Android自定义滑动开关按钮

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

    <!-- 声明属性集的名称 -->
    <declare-styleable name="MyToggleBtn">
        <!-- 声名一个属性  name是my_background   类型为 引用类型      引用资源ID -->
        <attr name="my_background" format="reference" />
        <!-- 声名一个属性  name是my_slide_btn   类型为 引用类型      引用资源ID -->
        <attr name="my_slide_btn" format="reference" />
        <!-- 声名一个属性  name是curr_state   类型为 boolean 类型 -->
        <attr name="curr_state" format="boolean" />
    </declare-styleable>

</resources>

<com.gnnuit.togglebutton.MyToggleButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        gnnuit:curr_state="true"
        gnnuit:my_background="@drawable/switch_background"
        gnnuit:my_slide_btn="@drawable/slide_button" />

package com.gnnuit.togglebutton;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class MyToggleButton extends View implements android.view.View.OnClickListener {
    private Bitmap backgroundBitmap;// 背景图片
    private Bitmap slideButtonBitmap;// 滑动按钮图片
    private Paint paint;
    private boolean currentState = false;// 当前状态
    private float left_slide;// 滑动按钮的左边界位置
    private float startX, lastX;// 记录滑动按钮滑动时的开始和结束位置
    private boolean isSlide = false;// 记录是否移动滑动按钮
    private float dist;

    /**
     * 在布局文件中声明此View，创建时由系统自动调用该构造方法
     * 
     * @param context
     * @param attrs
     */
    public MyToggleButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 获取自定义属性
        currentState = attrs.getAttributeBooleanValue("http://schemas.android.com/apk/res/com.gnnuit.togglebutton", "curr_state", false);
        
        int backgroundResourceId = attrs.getAttributeResourceValue("http://schemas.android.com/apk/res/com.gnnuit.togglebutton", "my_background", -1);
        if (backgroundResourceId == -1) {
            throw new RuntimeException("请设置背景图片");
        }
        backgroundBitmap = BitmapFactory.decodeResource(getResources(), backgroundResourceId);
        
        int slideBtnResourceId = attrs.getAttributeResourceValue("http://schemas.android.com/apk/res/com.gnnuit.togglebutton", "my_slide_btn", -1);
        if (slideBtnResourceId == -1) {
            throw new RuntimeException("请设置背景图片");
        }
        slideButtonBitmap = BitmapFactory.decodeResource(getResources(), slideBtnResourceId);

        if (currentState) {
            left_slide = backgroundBitmap.getWidth() - slideButtonBitmap.getWidth();
        }
        initView();// 初始化
    }

    /**
     * 初始化
     */
    private void initView() {
        // 初始化图片
        // backgroundBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.switch_background);
        // slideButtonBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.slide_button);
        // 初始化画笔
        paint = new Paint();
        paint.setAntiAlias(true);// 设置抗锯齿
        // 设置点击事件
        setOnClickListener(this);
    }

    @Override
    /**
     * 测量尺寸的回调方法
     */
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(backgroundBitmap.getWidth(), backgroundBitmap.getHeight());// 设置控件的宽和高，单位是像素
    }

    @Override
    /**
     * 绘制当前View的内容
     */
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(backgroundBitmap, 0, 0, paint);
        canvas.drawBitmap(slideButtonBitmap, left_slide, 0, paint);
    }

    @Override
    public void onClick(View v) {
        if (!isSlide) {
            currentState = !currentState;
            flushState();// 刷新界面
        }
    }

    /**
     * 刷新当前状态
     */
    private void flushState() {
        if (currentState) {
            left_slide = backgroundBitmap.getWidth() - slideButtonBitmap.getWidth();
        } else {
            left_slide = 0;
        }
        invalidate();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        super.onTouchEvent(event);
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            isSlide = false;
            startX = lastX = event.getX();
            break;

        case MotionEvent.ACTION_MOVE:
            lastX = event.getX();
            dist = lastX - startX;
            if (Math.abs(dist) > 5) {
                isSlide = true;
                left_slide += dist;
                flushShow();
                startX = event.getX();
            }
            break;
        case MotionEvent.ACTION_UP:
            if (isSlide) {
                if (left_slide > (backgroundBitmap.getWidth() - slideButtonBitmap.getWidth()) / 2) {
                    left_slide = backgroundBitmap.getWidth() - slideButtonBitmap.getWidth();
                    currentState = true;
                } else {
                    left_slide = 0;
                    currentState = false;
                }
                flushShow();
            }
            break;
        }
        return true;
    }

    /**
     * 刷新当前View
     */
    private void flushShow() {
        int maxLeftSlide = backgroundBitmap.getWidth() - slideButtonBitmap.getWidth();
        // left_slide的范围为0=<left_slide<=maxLeftSlide
        if (left_slide > maxLeftSlide) {
            left_slide = maxLeftSlide;
            currentState = true;
        } else if (left_slide < 0) {
            left_slide = 0;
            currentState = false;
        }
        invalidate();
    }
}