6.自定义view-侧边字母导航LetterNavigationBar

1.效果

2.实现原理

1.绘制右侧的字母

2.onTouchEvent 中获取点击、滑动的位置，在通过invalidate() 去重新绘制，

回调给activity去处理中间显示的文字

核心代码：

    @Override

    protected void onDraw(Canvas canvas) {

        mItemHeight = (getHeight() - getPaddingTop() - getPaddingBottom()) / mLetters.length;

        for (int i = 0; i < mLetters.length; i++) {

            int x = (int) (getWidth() / 2 - mPaint.measureText(mLetters[i]) / 2);

            int middleHeight = mItemHeight * i + getHeight() / mLetters.length / 2 + getPaddingTop();

            Paint.FontMetricsInt fontMetricsInt = mPaint.getFontMetricsInt();

            int dy = (fontMetricsInt.bottom - fontMetricsInt.top) / 2 - fontMetricsInt.bottom;

            int baseLine = middleHeight + dy;

            //当前滑动到的字母 高亮显示

            if (mCurrentLetter.equals(mLetters[i])) {

                canvas.drawText(mLetters[i], x, baseLine, mHighPaint);

            } else {

                canvas.drawText(mLetters[i], x, baseLine, mPaint);

            }

        }

    }

 @Override

    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()) {

            case MotionEvent.ACTION_MOVE:

                //获取当前触摸的下标

                int currentIndex = getCurrentIndex(event.getY());

                //防止重绘

                if (!mCurrentLetter.equals(mLetters[currentIndex])) {

                    mCurrentLetter = mLetters[currentIndex];

                    if (mLetterTouchListener != null) {

                        mLetterTouchListener.onTouch(mCurrentLetter, true);

                    }

                    invalidate();

                }

                break;

            case MotionEvent.ACTION_UP:

                if (mLetterTouchListener != null) {

                    mLetterTouchListener.onTouch(mCurrentLetter, false);

                }

                break;

        }

        return true;

    }

源码地址

巴特西

6.自定义view-侧边字母导航LetterNavigationBar

1.效果

2.实现原理

最新文章

热门文章