Android 继承framelayout，实现ScrollView 和 HorizontalScrollView 的效果
2024-08-31 16:30:41
有些项目，需要让控件或者布局进行水平和垂直同时能拖拽，当然，ScrollView 和 HorizontalScrollView 的结合写法是一种写法。但是，这么写用户体验效果不佳，会有迟钝感，因此推荐下面的写法。继承之FrameLayout，代码是在网上找的。
package com.test; import java.util.List; import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.FocusFinder;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.animation.AnimationUtils;
import android.widget.FrameLayout;
import android.widget.Scroller; /**
* Reference to ScrollView and HorizontalScrollView
*/
public class Myscroll extends FrameLayout {
static final int ANIMATED_SCROLL_GAP = ; static final float MAX_SCROLL_FACTOR = 0.5f; private long mLastScroll; private final Rect mTempRect = new Rect();
private Scroller mScroller; /**
* Flag to indicate that we are moving focus ourselves. This is so the
* code that watches for focus changes initiated outside this ScrollView
* knows that it does not have to do anything.
*/
private boolean mScrollViewMovedFocus; /**
* Position of the last motion event.
*/
private float mLastMotionY;
private float mLastMotionX; /**
* True when the layout has changed but the traversal has not come through yet.
* Ideally the view hierarchy would keep track of this for us.
*/
private boolean mIsLayoutDirty = true; /**
* The child to give focus to in the event that a child has requested focus while the
* layout is dirty. This prevents the scroll from being wrong if the child has not been
* laid out before requesting focus.
*/
private View mChildToScrollTo = null; /**
* True if the user is currently dragging this ScrollView around. This is
* not the same as 'is being flinged', which can be checked by
* mScroller.isFinished() (flinging begins when the user lifts his finger).
*/
private boolean mIsBeingDragged = false; /**
* Determines speed during touch scrolling
*/
private VelocityTracker mVelocityTracker; /**
* When set to true, the scroll view measure its child to make it fill the currently
* visible area.
*/
private boolean mFillViewport; /**
* Whether arrow scrolling is animated.
*/
private boolean mSmoothScrollingEnabled = true; private int mTouchSlop;
private int mMinimumVelocity;
private int mMaximumVelocity; /**
* ID of the active pointer. This is used to retain consistency during
* drags/flings if multiple pointers are used.
*/
private int mActivePointerId = INVALID_POINTER; /**
* Sentinel value for no current active pointer.
* Used by {@link #mActivePointerId}.
*/
private static final int INVALID_POINTER = -; private boolean mFlingEnabled = true; public Myscroll(Context context) {
this(context, null);
} public Myscroll(Context context, AttributeSet attrs) {
super(context, attrs);
initScrollView();
} @Override
protected float getTopFadingEdgeStrength() {
if (getChildCount() == ) {
return 0.0f;
} final int length = getVerticalFadingEdgeLength();
if (getScrollY() < length) {
return getScrollY() / (float) length;
} return 1.0f;
} @Override
protected float getLeftFadingEdgeStrength() {
if (getChildCount() == ) {
return 0.0f;
} final int length = getHorizontalFadingEdgeLength();
if (getScrollX() < length) {
return getScrollX() / (float) length;
} return 1.0f;
} @Override
protected float getRightFadingEdgeStrength() {
if (getChildCount() == ) {
return 0.0f;
} final int length = getHorizontalFadingEdgeLength();
final int rightEdge = getWidth() - getPaddingRight();
final int span = getChildAt().getRight() - getScrollX() - rightEdge;
if (span < length) {
return span / (float) length;
} return 1.0f;
} @Override
protected float getBottomFadingEdgeStrength() {
if (getChildCount() == ) {
return 0.0f;
} final int length = getVerticalFadingEdgeLength();
final int bottomEdge = getHeight() - getPaddingBottom();
final int span = getChildAt().getBottom() - getScrollY() - bottomEdge;
if (span < length) {
return span / (float) length;
} return 1.0f;
} /**
* @return The maximum amount this scroll view will scroll in response to
* an arrow event.
*/
public int getMaxScrollAmountV() {
return (int) (MAX_SCROLL_FACTOR * (getBottom() - getTop()));
} public int getMaxScrollAmountH() {
return (int) (MAX_SCROLL_FACTOR * (getRight() - getLeft()));
} private void initScrollView() {
mScroller = new Scroller(getContext());
setFocusable(true);
setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
setWillNotDraw(false);
final ViewConfiguration configuration = ViewConfiguration.get(getContext());
mTouchSlop = configuration.getScaledTouchSlop();
mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
} @Override
public void addView(View child) {
if (getChildCount() > ) {
throw new IllegalStateException("ScrollView can host only one direct child");
} super.addView(child);
} @Override
public void addView(View child, int index) {
if (getChildCount() > ) {
throw new IllegalStateException("ScrollView can host only one direct child");
} super.addView(child, index);
} @Override
public void addView(View child, ViewGroup.LayoutParams params) {
if (getChildCount() > ) {
throw new IllegalStateException("ScrollView can host only one direct child");
} super.addView(child, params);
} @Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if (getChildCount() > ) {
throw new IllegalStateException("ScrollView can host only one direct child");
} super.addView(child, index, params);
} /**
* @return Returns true this ScrollView can be scrolled
*/
private boolean canScrollV() {
View child = getChildAt();
if (child != null) {
int childHeight = child.getHeight();
return getHeight() < childHeight + getPaddingTop() + getPaddingBottom();
}
return false;
} private boolean canScrollH() {
View child = getChildAt();
if (child != null) {
int childWidth = child.getWidth();
return getWidth() < childWidth + getPaddingLeft() + getPaddingRight() ;
}
return false;
} /**
* Indicates whether this ScrollView's content is stretched to fill the viewport.
*
* @return True if the content fills the viewport, false otherwise.
*/
public boolean isFillViewport() {
return mFillViewport;
} /**
* Indicates this ScrollView whether it should stretch its content height to fill
* the viewport or not.
*
* @param fillViewport True to stretch the content's height to the viewport's
* boundaries, false otherwise.
*/
public void setFillViewport(boolean fillViewport) {
if (fillViewport != mFillViewport) {
mFillViewport = fillViewport;
requestLayout();
}
} /**
* @return Whether arrow scrolling will animate its transition.
*/
public boolean isSmoothScrollingEnabled() {
return mSmoothScrollingEnabled;
} /**
* Set whether arrow scrolling will animate its transition.
* @param smoothScrollingEnabled whether arrow scrolling will animate its transition
*/
public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {
mSmoothScrollingEnabled = smoothScrollingEnabled;
} @Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (!mFillViewport) {
return;
} final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (heightMode == MeasureSpec.UNSPECIFIED && widthMode == MeasureSpec.UNSPECIFIED) {
return;
} if (getChildCount() > ) {
final View child = getChildAt();
int height = getMeasuredHeight();
int width = getMeasuredWidth();
if (child.getMeasuredHeight() < height || child.getMeasuredWidth() < width) {
width -= getPaddingLeft();
width -= getPaddingRight();
int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); height -= getPaddingTop();
height -= getPaddingBottom();
int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
}
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
// Let the focused view and/or our descendants get the key first
return super.dispatchKeyEvent(event) || executeKeyEvent(event);
} /**
* You can call this function yourself to have the scroll view perform
* scrolling from a key event, just as if the event had been dispatched to
* it by the view hierarchy.
*
* @param event The key event to execute.
* @return Return true if the event was handled, else false.
*/
public boolean executeKeyEvent(KeyEvent event) {
mTempRect.setEmpty(); boolean handled = false; if (event.getAction() == KeyEvent.ACTION_DOWN) {
switch (event.getKeyCode()) {
case KeyEvent.KEYCODE_DPAD_LEFT:
if(canScrollH()){
if (!event.isAltPressed()) {
handled = arrowScrollH(View.FOCUS_LEFT);
} else {
handled = fullScrollH(View.FOCUS_LEFT);
}
}
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
if(canScrollH()){
if (!event.isAltPressed()) {
handled = arrowScrollH(View.FOCUS_RIGHT);
} else {
handled = fullScrollH(View.FOCUS_RIGHT);
}
}
break;
case KeyEvent.KEYCODE_DPAD_UP:
if(canScrollV()){
if (!event.isAltPressed()) {
handled = arrowScrollV(View.FOCUS_UP);
} else {
handled = fullScrollV(View.FOCUS_UP);
}
}
break;
case KeyEvent.KEYCODE_DPAD_DOWN:
if(canScrollV()){
if (!event.isAltPressed()) {
handled = arrowScrollV(View.FOCUS_DOWN);
} else {
handled = fullScrollV(View.FOCUS_DOWN);
}
}
break;
}
}
return handled;
} private boolean inChild(int x, int y) {
if (getChildCount() > ) {
final int scrollX = getScrollX();
final int scrollY = getScrollY();
final View child = getChildAt();
return !(y < child.getTop() - scrollY
|| y >= child.getBottom() - scrollY
|| x < child.getLeft() - scrollX
|| x >= child.getRight() - scrollX);
}
return false;
} @Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onMotionEvent will be called and we do the actual
* scrolling there.
*/ /*
* Shortcut the most recurring case: the user is in the dragging
* state and he is moving his finger. We want to intercept this
* motion.
*/
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) {
return true;
} switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_MOVE: {
/*
* mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
* whether the user has moved far enough from his original down touch.
*/ /*
* Locally do absolute value. mLastMotionY is set to the y value
* of the down event.
*/
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
// If we don't have a valid id, the touch down wasn't on content.
break;
} final int pointerIndex = ev.findPointerIndex(activePointerId);
final float y = ev.getY(pointerIndex);
final int yDiff = (int) Math.abs(y - mLastMotionY);
if (yDiff > mTouchSlop) {
mIsBeingDragged = true;
mLastMotionY = y;
}
final float x = ev.getX(pointerIndex);
final int xDiff = (int) Math.abs(x - mLastMotionX);
if (xDiff > mTouchSlop) {
mIsBeingDragged = true;
mLastMotionX = x;
}
break;
} case MotionEvent.ACTION_DOWN: {
final float x = ev.getX();
final float y = ev.getY();
if (!inChild((int)x, (int) y)) {
mIsBeingDragged = false;
break;
} /*
* Remember location of down touch.
* ACTION_DOWN always refers to pointer index 0.
*/
mLastMotionY = y;
mLastMotionX = x;
mActivePointerId = ev.getPointerId(); /*
* If being flinged and user touches the screen, initiate drag;
* otherwise don't. mScroller.isFinished should be false when
* being flinged.
*/
mIsBeingDragged = !mScroller.isFinished();
break;
} case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
/* Release the drag */
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
} /*
* The only time we want to intercept motion events is if we are in the
* drag mode.
*/
return mIsBeingDragged;
} @Override
public boolean onTouchEvent(MotionEvent ev) { if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != ) {
// Don't handle edge touches immediately -- they may actually belong to one of our
// descendants.
return false;
} if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev); final int action = ev.getAction(); switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
final float x = ev.getX();
final float y = ev.getY();
if (!(mIsBeingDragged = inChild((int) x, (int) y))) {
return false;
} /*
* If being flinged and user touches, stop the fling. isFinished
* will be false if being flinged.
*/
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
} // Remember where the motion event started
mLastMotionY = y;
mLastMotionX = x;
mActivePointerId = ev.getPointerId();
break;
}
case MotionEvent.ACTION_MOVE:
if (mIsBeingDragged) {
// Scroll to follow the motion event
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
final float y = ev.getY(activePointerIndex);
final int deltaY = (int) (mLastMotionY - y);
mLastMotionY = y; final float x = ev.getX(activePointerIndex);
final int deltaX = (int) (mLastMotionX - x);
mLastMotionX = x; scrollBy(deltaX, deltaY);
}
break;
case MotionEvent.ACTION_UP:
if (mIsBeingDragged) {
if(mFlingEnabled){
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(, mMaximumVelocity);
int initialVelocitx = (int) velocityTracker.getXVelocity();
int initialVelocity = (int) velocityTracker.getYVelocity();
// int initialVelocitx = (int) velocityTracker.getXVelocity(mActivePointerId);
// int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); if (getChildCount() > ) {
if(Math.abs(initialVelocitx) > initialVelocitx || Math.abs(initialVelocity) > mMinimumVelocity) {
fling(-initialVelocitx, -initialVelocity);
} }
} mActivePointerId = INVALID_POINTER;
mIsBeingDragged = false; if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged && getChildCount() > ) {
mActivePointerId = INVALID_POINTER;
mIsBeingDragged = false;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
return true;
} private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >>
MotionEvent.ACTION_POINTER_ID_SHIFT;
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == ? : ;
mLastMotionX = ev.getX(newPointerIndex);
mLastMotionY = ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
/**
* <p>
* Finds the next focusable component that fits in the specified bounds.
* </p>
*
* @param topFocus look for a candidate is the one at the top of the bounds
* if topFocus is true, or at the bottom of the bounds if topFocus is
* false
* @param top the top offset of the bounds in which a focusable must be
* found
* @param bottom the bottom offset of the bounds in which a focusable must
* be found
* @return the next focusable component in the bounds or null if none can
* be found
*/
private View findFocusableViewInBoundsV(boolean topFocus, int top, int bottom) { List<View> focusables = getFocusables(View.FOCUS_FORWARD);
View focusCandidate = null; /*
* A fully contained focusable is one where its top is below the bound's
* top, and its bottom is above the bound's bottom. A partially
* contained focusable is one where some part of it is within the
* bounds, but it also has some part that is not within bounds. A fully contained
* focusable is preferred to a partially contained focusable.
*/
boolean foundFullyContainedFocusable = false; int count = focusables.size();
for (int i = ; i < count; i++) {
View view = focusables.get(i);
int viewTop = view.getTop();
int viewBottom = view.getBottom(); if (top < viewBottom && viewTop < bottom) {
/*
* the focusable is in the target area, it is a candidate for
* focusing
*/ final boolean viewIsFullyContained = (top < viewTop) &&
(viewBottom < bottom); if (focusCandidate == null) {
/* No candidate, take this one */
focusCandidate = view;
foundFullyContainedFocusable = viewIsFullyContained;
} else {
final boolean viewIsCloserToBoundary =
(topFocus && viewTop < focusCandidate.getTop()) ||
(!topFocus && viewBottom > focusCandidate
.getBottom()); if (foundFullyContainedFocusable) {
if (viewIsFullyContained && viewIsCloserToBoundary) {
/*
* We're dealing with only fully contained views, so
* it has to be closer to the boundary to beat our
* candidate
*/
focusCandidate = view;
}
} else {
if (viewIsFullyContained) {
/* Any fully contained view beats a partially contained view */
focusCandidate = view;
foundFullyContainedFocusable = true;
} else if (viewIsCloserToBoundary) {
/*
* Partially contained view beats another partially
* contained view if it's closer
*/
focusCandidate = view;
}
}
}
}
} return focusCandidate;
} private View findFocusableViewInBoundsH(boolean leftFocus, int left, int right) { List<View> focusables = getFocusables(View.FOCUS_FORWARD);
View focusCandidate = null; /*
* A fully contained focusable is one where its left is below the bound's
* left, and its right is above the bound's right. A partially
* contained focusable is one where some part of it is within the
* bounds, but it also has some part that is not within bounds. A fully contained
* focusable is preferred to a partially contained focusable.
*/
boolean foundFullyContainedFocusable = false; int count = focusables.size();
for (int i = ; i < count; i++) {
View view = focusables.get(i);
int viewLeft = view.getLeft();
int viewRight = view.getRight(); if (left < viewRight && viewLeft < right) {
/*
* the focusable is in the target area, it is a candidate for
* focusing
*/ final boolean viewIsFullyContained = (left < viewLeft) &&
(viewRight < right); if (focusCandidate == null) {
/* No candidate, take this one */
focusCandidate = view;
foundFullyContainedFocusable = viewIsFullyContained;
} else {
final boolean viewIsCloserToBoundary =
(leftFocus && viewLeft < focusCandidate.getLeft()) ||
(!leftFocus && viewRight > focusCandidate.getRight()); if (foundFullyContainedFocusable) {
if (viewIsFullyContained && viewIsCloserToBoundary) {
/*
* We're dealing with only fully contained views, so
* it has to be closer to the boundary to beat our
* candidate
*/
focusCandidate = view;
}
} else {
if (viewIsFullyContained) {
/* Any fully contained view beats a partially contained view */
focusCandidate = view;
foundFullyContainedFocusable = true;
} else if (viewIsCloserToBoundary) {
/*
* Partially contained view beats another partially
* contained view if it's closer
*/
focusCandidate = view;
}
}
}
}
} return focusCandidate;
} /**
* <p>Handles scrolling in response to a "home/end" shortcut press. This
* method will scroll the view to the top or bottom and give the focus
* to the topmost/bottommost component in the new visible area. If no
* component is a good candidate for focus, this scrollview reclaims the
* focus.</p>
*
* @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
* to go the top of the view or
* {@link android.view.View#FOCUS_DOWN} to go the bottom
* @return true if the key event is consumed by this method, false otherwise
*/
public boolean fullScrollV(int direction) {
boolean down = direction == View.FOCUS_DOWN;
int height = getHeight(); mTempRect.top = ;
mTempRect.bottom = height; if (down) {
int count = getChildCount();
if (count > ) {
View view = getChildAt(count - );
mTempRect.bottom = view.getBottom();
mTempRect.top = mTempRect.bottom - height;
}
} return scrollAndFocusV(direction, mTempRect.top, mTempRect.bottom);
} public boolean fullScrollH(int direction) {
boolean right = direction == View.FOCUS_RIGHT;
int width = getWidth(); mTempRect.left = ;
mTempRect.right = width; if (right) {
int count = getChildCount();
if (count > ) {
View view = getChildAt();
mTempRect.right = view.getRight();
mTempRect.left = mTempRect.right - width;
}
} return scrollAndFocusH(direction, mTempRect.left, mTempRect.right);
} /**
* <p>Scrolls the view to make the area defined by <code>top</code> and
* <code>bottom</code> visible. This method attempts to give the focus
* to a component visible in this area. If no component can be focused in
* the new visible area, the focus is reclaimed by this scrollview.</p>
*
* @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
* to go upward
* {@link android.view.View#FOCUS_DOWN} to downward
* @param top the top offset of the new area to be made visible
* @param bottom the bottom offset of the new area to be made visible
* @return true if the key event is consumed by this method, false otherwise
*/
private boolean scrollAndFocusV(int direction, int top, int bottom) {
boolean handled = true; int height = getHeight();
int containerTop = getScrollY();
int containerBottom = containerTop + height;
boolean up = direction == View.FOCUS_UP; View newFocused = findFocusableViewInBoundsV(up, top, bottom);
if (newFocused == null) {
newFocused = this;
} if (top >= containerTop && bottom <= containerBottom) {
handled = false;
} else {
int delta = up ? (top - containerTop) : (bottom - containerBottom);
doScrollY(delta);
} if (newFocused != findFocus() && newFocused.requestFocus(direction)) {
mScrollViewMovedFocus = true;
mScrollViewMovedFocus = false;
} return handled;
} private boolean scrollAndFocusH(int direction, int left, int right) {
boolean handled = true; int width = getWidth();
int containerLeft = getScrollX();
int containerRight = containerLeft + width;
boolean goLeft = direction == View.FOCUS_LEFT; View newFocused = findFocusableViewInBoundsH(goLeft, left, right);
if (newFocused == null) {
newFocused = this;
} if (left >= containerLeft && right <= containerRight) {
handled = false;
} else {
int delta = goLeft ? (left - containerLeft) : (right - containerRight);
doScrollX(delta);
} if (newFocused != findFocus() && newFocused.requestFocus(direction)) {
mScrollViewMovedFocus = true;
mScrollViewMovedFocus = false;
} return handled;
} /**
* Handle scrolling in response to an up or down arrow click.
*
* @param direction The direction corresponding to the arrow key that was
* pressed
* @return True if we consumed the event, false otherwise
*/
public boolean arrowScrollV(int direction) { View currentFocused = findFocus();
if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); final int maxJump = getMaxScrollAmountV(); if (nextFocused != null && isWithinDeltaOfScreenV(nextFocused, maxJump, getHeight())) {
nextFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(nextFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);
doScrollY(scrollDelta);
nextFocused.requestFocus(direction);
} else {
// no new focus
int scrollDelta = maxJump; if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) {
scrollDelta = getScrollY();
} else if (direction == View.FOCUS_DOWN) {
if (getChildCount() > ) {
int daBottom = getChildAt().getBottom(); int screenBottom = getScrollY() + getHeight(); if (daBottom - screenBottom < maxJump) {
scrollDelta = daBottom - screenBottom;
}
}
}
if (scrollDelta == ) {
return false;
}
doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta);
} if (currentFocused != null && currentFocused.isFocused()
&& isOffScreenV(currentFocused)) {
// previously focused item still has focus and is off screen, give
// it up (take it back to ourselves)
// (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are
// sure to
// get it)
final int descendantFocusability = getDescendantFocusability(); // save
setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);
requestFocus();
setDescendantFocusability(descendantFocusability); // restore
}
return true;
} public boolean arrowScrollH(int direction) { View currentFocused = findFocus();
if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); final int maxJump = getMaxScrollAmountH(); if (nextFocused != null && isWithinDeltaOfScreenH(nextFocused, maxJump)) {
nextFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(nextFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);
doScrollX(scrollDelta);
nextFocused.requestFocus(direction);
} else {
// no new focus
int scrollDelta = maxJump; if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) {
scrollDelta = getScrollX();
} else if (direction == View.FOCUS_RIGHT && getChildCount() > ) { int daRight = getChildAt().getRight(); int screenRight = getScrollX() + getWidth(); if (daRight - screenRight < maxJump) {
scrollDelta = daRight - screenRight;
}
}
if (scrollDelta == ) {
return false;
}
doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta);
} if (currentFocused != null && currentFocused.isFocused()
&& isOffScreenH(currentFocused)) {
// previously focused item still has focus and is off screen, give
// it up (take it back to ourselves)
// (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are
// sure to
// get it)
final int descendantFocusability = getDescendantFocusability(); // save
setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);
requestFocus();
setDescendantFocusability(descendantFocusability); // restore
}
return true;
}
/**
* @return whether the descendant of this scroll view is scrolled off
* screen.
*/
private boolean isOffScreenV(View descendant) {
return !isWithinDeltaOfScreenV(descendant, , getHeight());
} private boolean isOffScreenH(View descendant) {
return !isWithinDeltaOfScreenH(descendant, );
} /**
* @return whether the descendant of this scroll view is within delta
* pixels of being on the screen.
*/
private boolean isWithinDeltaOfScreenV(View descendant, int delta, int height) {
descendant.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(descendant, mTempRect); return (mTempRect.bottom + delta) >= getScrollY()
&& (mTempRect.top - delta) <= (getScrollY() + height);
} private boolean isWithinDeltaOfScreenH(View descendant, int delta) {
descendant.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(descendant, mTempRect); return (mTempRect.right + delta) >= getScrollX()
&& (mTempRect.left - delta) <= (getScrollX() + getWidth());
} /**
* Smooth scroll by a Y delta
*
* @param delta the number of pixels to scroll by on the Y axis
*/
private void doScrollY(int delta) {
if (delta != ) {
if (mSmoothScrollingEnabled) {
smoothScrollBy(, delta);
} else {
scrollBy(, delta);
}
}
} private void doScrollX(int delta) {
if (delta != ) {
if (mSmoothScrollingEnabled) {
smoothScrollBy(delta, );
} else {
scrollBy(delta, );
}
}
} /**
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param dx the number of pixels to scroll by on the X axis
* @param dy the number of pixels to scroll by on the Y axis
*/
public void smoothScrollBy(int dx, int dy) {
if (getChildCount() == ) {
// Nothing to do.
return;
}
long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
if (duration > ANIMATED_SCROLL_GAP) {
final int height = getHeight() - getPaddingBottom() - getPaddingTop();
final int bottom = getChildAt().getHeight();
final int maxY = Math.max(, bottom - height);
final int scrollY = getScrollY();
dy = Math.max(, Math.min(scrollY + dy, maxY)) - scrollY; final int width = getWidth() - getPaddingRight() - getPaddingLeft();
final int right = getChildAt().getWidth();
final int maxX = Math.max(, right - width);
final int scrollX = getScrollX();
dx = Math.max(, Math.min(scrollX + dx, maxX)) - scrollX; mScroller.startScroll(scrollX, scrollY, dx, dy);
invalidate();
} else {
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
scrollBy(dx, dy);
}
mLastScroll = AnimationUtils.currentAnimationTimeMillis();
} /**
* Like {@link #scrollTo}, but scroll smoothly instead of immediately.
*
* @param x the position where to scroll on the X axis
* @param y the position where to scroll on the Y axis
*/
public final void smoothScrollTo(int x, int y) {
smoothScrollBy(x - getScrollX(), y - getScrollY());
} /**
* <p>The scroll range of a scroll view is the overall height of all of its
* children.</p>
*/
@Override
protected int computeVerticalScrollRange() {
final int count = getChildCount();
final int contentHeight = getHeight() - getPaddingBottom() - getPaddingTop();
if (count == ) {
return contentHeight;
} return getChildAt().getBottom();
} @Override
protected int computeHorizontalScrollRange() {
final int count = getChildCount();
final int contentWidth = getWidth() - getPaddingLeft() - getPaddingRight();
if (count == ) {
return contentWidth;
} return getChildAt().getRight();
} @Override
protected int computeVerticalScrollOffset() {
return Math.max(, super.computeVerticalScrollOffset());
} @Override
protected int computeHorizontalScrollOffset() {
return Math.max(, super.computeHorizontalScrollOffset());
} @Override
protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
int childWidthMeasureSpec;
int childHeightMeasureSpec; childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(, MeasureSpec.UNSPECIFIED); childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
} @Override
protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
int parentHeightMeasureSpec, int heightUsed) {
final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);
final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
} @Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
// This is called at drawing time by ViewGroup. We don't want to
// re-show the scrollbars at this point, which scrollTo will do,
// so we replicate most of scrollTo here.
//
// It's a little odd to call onScrollChanged from inside the drawing.
//
// It is, except when you remember that computeScroll() is used to
// animate scrolling. So unless we want to defer the onScrollChanged()
// until the end of the animated scrolling, we don't really have a
// choice here.
//
// I agree. The alternative, which I think would be worse, is to post
// something and tell the subclasses later. This is bad because there
// will be a window where mScrollX/Y is different from what the app
// thinks it is.
//
int x = mScroller.getCurrX();
int y = mScroller.getCurrY(); if (getChildCount() > ) {
View child = getChildAt();
x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
super.scrollTo(x, y);
}
awakenScrollBars(); // Keep on drawing until the animation has finished.
postInvalidate();
}
} /**
* Scrolls the view to the given child.
*
* @param child the View to scroll to
*/
private void scrollToChild(View child) {
child.getDrawingRect(mTempRect); /* Offset from child's local coordinates to ScrollView coordinates */
offsetDescendantRectToMyCoords(child, mTempRect); int scrollDeltaV = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);
int scrollDeltaH = computeScrollDeltaToGetChildRectOnScreenH(mTempRect); if (scrollDeltaH != || scrollDeltaV != ) {
scrollBy(scrollDeltaH, scrollDeltaV);
}
} /**
* If rect is off screen, scroll just enough to get it (or at least the
* first screen size chunk of it) on screen.
*
* @param rect The rectangle.
* @param immediate True to scroll immediately without animation
* @return true if scrolling was performed
*/
private boolean scrollToChildRect(Rect rect, boolean immediate) {
final int deltaV = computeScrollDeltaToGetChildRectOnScreenV(rect);
final int deltaH = computeScrollDeltaToGetChildRectOnScreenH(rect);
final boolean scroll = deltaH != || deltaV != ;
if (scroll) {
if (immediate) {
scrollBy(deltaH, deltaV);
} else {
smoothScrollBy(deltaH, deltaV);
}
}
return scroll;
}
/**
* Compute the amount to scroll in the Y direction in order to get
* a rectangle completely on the screen (or, if taller than the screen,
* at least the first screen size chunk of it).
*
* @param rect The rect.
* @return The scroll delta.
*/
protected int computeScrollDeltaToGetChildRectOnScreenV(Rect rect) {
if (getChildCount() == ) return ; int height = getHeight();
int screenTop = getScrollY();
int screenBottom = screenTop + height; int fadingEdge = getVerticalFadingEdgeLength(); // leave room for top fading edge as long as rect isn't at very top
if (rect.top > ) {
screenTop += fadingEdge;
} // leave room for bottom fading edge as long as rect isn't at very bottom
if (rect.bottom < getChildAt().getHeight()) {
screenBottom -= fadingEdge;
} int scrollYDelta = ; if (rect.bottom > screenBottom && rect.top > screenTop) {
// need to move down to get it in view: move down just enough so
// that the entire rectangle is in view (or at least the first
// screen size chunk). if (rect.height() > height) {
// just enough to get screen size chunk on
scrollYDelta += (rect.top - screenTop);
} else {
// get entire rect at bottom of screen
scrollYDelta += (rect.bottom - screenBottom);
} // make sure we aren't scrolling beyond the end of our content
int bottom = getChildAt().getBottom();
int distanceToBottom = bottom - screenBottom;
scrollYDelta = Math.min(scrollYDelta, distanceToBottom); } else if (rect.top < screenTop && rect.bottom < screenBottom) {
// need to move up to get it in view: move up just enough so that
// entire rectangle is in view (or at least the first screen
// size chunk of it). if (rect.height() > height) {
// screen size chunk
scrollYDelta -= (screenBottom - rect.bottom);
} else {
// entire rect at top
scrollYDelta -= (screenTop - rect.top);
} // make sure we aren't scrolling any further than the top our content
scrollYDelta = Math.max(scrollYDelta, -getScrollY());
}
return scrollYDelta;
} protected int computeScrollDeltaToGetChildRectOnScreenH(Rect rect) {
if (getChildCount() == ) return ; int width = getWidth();
int screenLeft = getScrollX();
int screenRight = screenLeft + width; int fadingEdge = getHorizontalFadingEdgeLength(); // leave room for left fading edge as long as rect isn't at very left
if (rect.left > ) {
screenLeft += fadingEdge;
} // leave room for right fading edge as long as rect isn't at very right
if (rect.right < getChildAt().getWidth()) {
screenRight -= fadingEdge;
} int scrollXDelta = ; if (rect.right > screenRight && rect.left > screenLeft) {
// need to move right to get it in view: move right just enough so
// that the entire rectangle is in view (or at least the first
// screen size chunk). if (rect.width() > width) {
// just enough to get screen size chunk on
scrollXDelta += (rect.left - screenLeft);
} else {
// get entire rect at right of screen
scrollXDelta += (rect.right - screenRight);
} // make sure we aren't scrolling beyond the end of our content
int right = getChildAt().getRight();
int distanceToRight = right - screenRight;
scrollXDelta = Math.min(scrollXDelta, distanceToRight); } else if (rect.left < screenLeft && rect.right < screenRight) {
// need to move right to get it in view: move right just enough so that
// entire rectangle is in view (or at least the first screen
// size chunk of it). if (rect.width() > width) {
// screen size chunk
scrollXDelta -= (screenRight - rect.right);
} else {
// entire rect at left
scrollXDelta -= (screenLeft - rect.left);
} // make sure we aren't scrolling any further than the left our content
scrollXDelta = Math.max(scrollXDelta, -getScrollX());
}
return scrollXDelta;
} @Override
public void requestChildFocus(View child, View focused) {
if (!mScrollViewMovedFocus) {
if (!mIsLayoutDirty) {
scrollToChild(focused);
} else {
// The child may not be laid out yet, we can't compute the scroll yet
mChildToScrollTo = focused;
}
}
super.requestChildFocus(child, focused);
} /**
* When looking for focus in children of a scroll view, need to be a little
* more careful not to give focus to something that is scrolled off screen.
*
* This is more expensive than the default {@link android.view.ViewGroup}
* implementation, otherwise this behavior might have been made the default.
*/
@Override
protected boolean onRequestFocusInDescendants(int direction,
Rect previouslyFocusedRect) { // convert from forward / backward notation to up / down / left / right
// (ugh).
// TODO:
// if (direction == View.FOCUS_FORWARD) {
// direction = View.FOCUS_RIGHT;
// } else if (direction == View.FOCUS_BACKWARD) {
// direction = View.FOCUS_LEFT;
// } final View nextFocus = previouslyFocusedRect == null ?
FocusFinder.getInstance().findNextFocus(this, null, direction) :
FocusFinder.getInstance().findNextFocusFromRect(this,
previouslyFocusedRect, direction); if (nextFocus == null) {
return false;
} // if (isOffScreenH(nextFocus)) {
// return false;
// } return nextFocus.requestFocus(direction, previouslyFocusedRect);
} @Override
public boolean requestChildRectangleOnScreen(View child, Rect rectangle,
boolean immediate) {
// offset into coordinate space of this scroll view
rectangle.offset(child.getLeft() - child.getScrollX(),
child.getTop() - child.getScrollY()); return scrollToChildRect(rectangle, immediate);
} @Override
public void requestLayout() {
mIsLayoutDirty = true;
super.requestLayout();
} @Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
mIsLayoutDirty = false;
// Give a child focus if it needs it
if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) {
scrollToChild(mChildToScrollTo);
}
mChildToScrollTo = null; // Calling this with the present values causes it to re-clam them
scrollTo(getScrollX(), getScrollY());
} @Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh); View currentFocused = findFocus();
if (null == currentFocused || this == currentFocused)
return; // If the currently-focused view was visible on the screen when the
// screen was at the old height, then scroll the screen to make that
// view visible with the new screen height.
if (isWithinDeltaOfScreenV(currentFocused, , oldh)) {
currentFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(currentFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);
doScrollY(scrollDelta);
} final int maxJump = getRight() - getLeft();
if (isWithinDeltaOfScreenH(currentFocused, maxJump)) {
currentFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(currentFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);
doScrollX(scrollDelta);
}
} /**
* Return true if child is an descendant of parent, (or equal to the parent).
*/
private boolean isViewDescendantOf(View child, View parent) {
if (child == parent) {
return true;
} final ViewParent theParent = child.getParent();
return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent);
} /**
* Fling the scroll view
*
* @param velocityY The initial velocity in the Y direction. Positive
* numbers mean that the finger/cursor is moving down the screen,
* which means we want to scroll towards the top.
*/
public void fling(int velocityX, int velocityY) {
if (getChildCount() > ) {
int width = getWidth() - getPaddingRight() - getPaddingLeft();
int right = getChildAt().getWidth(); int height = getHeight() - getPaddingBottom() - getPaddingTop();
int bottom = getChildAt().getHeight(); mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY,
, Math.max(, right - width),
, Math.max(, bottom - height)); // final boolean movingDown = velocityX > 0 || velocityY > 0;
//
// View newFocused =
// findFocusableViewInMyBoundsV(movingDown, mScroller.getFinalY(), findFocus());
// if (newFocused == null) {
// newFocused = this;
// }
//
// if (newFocused != findFocus()
// && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) {
// mScrollViewMovedFocus = true;
// mScrollViewMovedFocus = false;
// } invalidate();
}
} /**
* {@inheritDoc}
*
* <p>This version also clamps the scrolling to the bounds of our child.
*/
@Override
public void scrollTo(int x, int y) {
// we rely on the fact the View.scrollBy calls scrollTo.
if (getChildCount() > ) {
View child = getChildAt();
x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
if (x != getScrollX() || y != getScrollY()) {
super.scrollTo(x, y);
}
}
} private int clamp(int n, int my, int child) {
if (my >= child || n < ) {
/* my >= child is this case:
* |--------------- me ---------------|
* |------ child ------|
* or
* |--------------- me ---------------|
* |------ child ------|
* or
* |--------------- me ---------------|
* |------ child ------|
*
* n < 0 is this case:
* |------ me ------|
* |-------- child --------|
* |-- mScrollX --|
*/
return ;
}
if ((my+n) > child) {
/* this case:
* |------ me ------|
* |------ child ------|
* |-- mScrollX --|
*/
return child-my;
}
return n;
} public boolean isFlingEnabled() {
return mFlingEnabled;
} public void setFlingEnabled(boolean flingEnabled) {
this.mFlingEnabled = flingEnabled;
}
}
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