简介

总结下之前看的自定义View的内容，结合一个简单的例子，阐述下基本用法和大致的使用流程，这个例子比较简单，更复杂的自定义View，随着自己的学习，后面再慢慢添加。作为一个Android开发者，这部分应该是不可或缺的。

自定义属性

位置：res/values/attrs.xml

格式：

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <declare-styleable name="name_of_style">

        <attr name="name_of_attr" format="reference|string|color|boolean|dimension|enum|flag|float|fraction|integer"/>

    </declare-styleable>

</resources>

format	意义
reference	参考某一资源ID, 如R.drawable.xxx
string	字符串
color	颜色
boolean	布尔值
dimension	尺寸值
enum	枚举值,例如
flag	位或运算，例如：
float	浮点数
fraction	百分数，例如pivotX,pivotY这一类属性
integer	整数

获取自定义属性

TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.name_of_style);

Color mColor = typedArray.getColor(R.styleable.name_of_style_name_of_attr, Color.BLUE);//其他的属性获取类似

typedArray.recycle();//记得回收

名字：

R.styleable.{name_of_style}

R.styleable.{name_of_style}_{name_of_attr}

举个栗子

举个栗子，实现一个背景为渐变色的圆角按钮，圆角半径，开始颜色，中心颜色，结束颜色，渐变方向用户可自定义。

attrs.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <declare-styleable name="CornerButton">

        <attr name="corner_radius" format="dimension" />

        <attr name="background_start_color" format="color" />

        <attr name="background_center_color" format="color" />

        <attr name="background_end_color" format="color" />

        <attr name="backgrouund_gradient_orientation">

            <enum name="TOP_BOTTOM" value="0" />

            <enum name="TR_BL" value="1" />

            <enum name="RIGHT_LEFT" value="2" />

            <enum name="BR_TL" value="3" />

            <enum name="BOTTOM_TOP" value="4" />

            <enum name="BL_TR" value="5" />

            <enum name="LEFT_RIGHT" value="6" />

            <enum name="TL_BR" value="7" />

        </attr>

    </declare-styleable>

</resources>

CornerButton

public class CornerButton extends Button {

    private GradientDrawable mBg;

    private float mRandius;

    private int mStartColor;

    private int mCenterColor;

    private int mEndColor;

    private int mOrientation;

    public CornerButton(Context context, AttributeSet attrs) {

        super(context, attrs);

        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.CornerButton);

        mRandius = typedArray.getDimension(R.styleable.CornerButton_corner_radius, 10);

        mStartColor = typedArray.getColor(R.styleable.CornerButton_background_start_color, Color.BLUE);

        mCenterColor = typedArray.getColor(R.styleable.CornerButton_background_center_color, Color.GREEN);

        mEndColor = typedArray.getColor(R.styleable.CornerButton_background_end_color, Color.BLACK);

        mOrientation = typedArray.getInt(R.styleable.CornerButton_backgrouund_gradient_orientation, 0);

        typedArray.recycle();

        int[] colors = {mStartColor, mCenterColor, mEndColor};

        mBg = new GradientDrawable();

        mBg.setCornerRadius(mRandius);

        mBg.setOrientation(Orientation.TR_BL);

        mBg.setColors(colors);

        switch (mOrientation) {

            case 0:

                mBg.setOrientation(Orientation.TOP_BOTTOM);

                break;

            case 1:

                mBg.setOrientation(Orientation.TR_BL);

                break;

            case 2:

                mBg.setOrientation(Orientation.RIGHT_LEFT);

                break;

            case 3:

                mBg.setOrientation(Orientation.BR_TL);

                break;

            case 4:

                mBg.setOrientation(Orientation.BOTTOM_TOP);

                break;

            case 5:

                mBg.setOrientation(Orientation.BL_TR);

                break;

            case 6:

                mBg.setOrientation(Orientation.LEFT_RIGHT);

                break;

            case 7:

                mBg.setOrientation(Orientation.TL_BR);

                break;

        }

        this.setBackground(mBg);

    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:yidong="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/activity_main"

    android:layout_width="match_parent" android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="gs.com.customview.MainActivity">

    <gs.com.customview.CornerButton

        android:id="@+id/cb_content"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        yidong:background_start_color="#CCFF0000"

        yidong:background_center_color="#CCAADD00"

        yidong:background_end_color="#CC00EEFF"

        yidong:corner_radius="100dp"

        yidong:backgrouund_gradient_orientation="BOTTOM_TOP"

        />

</RelativeLayout>

xmlns:yidong=”http://schemas.android.com/apk/res-auto”

和

yidong:corner_radius=”100dp”

XML命名空间和属性的Tag对应。

实际效果