绘制 ToggleButton --重写view

package com.example.compoundbuttonview.view;

import com.example.compoundbuttonview.R;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

public class SlideSwitchView extends View{
    /** Switch底部样式图片 */
    private Bitmap mSwitchBottom;
    /** Switch 当前样式  */
    private Bitmap mSwitchThumb;
    /** Switch无操作情况下的样式  */
    private Bitmap mSwitchThumbNormal;
    /** Switch当前手指触摸式的样式  */
    private Bitmap mSwitchThumbPressed;
    /** Switch 框架  */
    private Bitmap mSwitchFrame;
    private Bitmap mSwitchMask;
    private float mCurrentX = 0;
    /** Switch 开关状态，默认是  开：true  */
    private boolean mSwitchOn = true;
    /** Switch 最大移动距离   */
    private int mMoveLength;
    /** 第一次按下的有效区域 */
    private float mLastX = 0;
    /** 绘制的目标区域大小  */
    private Rect mDest = null; 
    /** 截取源图片的大小  */
    private Rect mSrc = null;
    /** Switch 移动的偏移量  */
    private int mMoveDeltX = 0;
    /** 画笔工具  */
    private Paint mPaint = null;
    /** Switch 状态监听接口  */
    private OnSwitchChangedListener switchListener = null;
    private boolean mFlag = false;
    /** enabled 属性 为 true */
    private boolean mEnabled = true;
    /** 最大透明度，就是不透明 */
    private final int MAX_ALPHA = 255;
    /** 当前透明度，这里主要用于如果控件的enable属性为false时候设置半透明 ，即不可以点击 */
    private int mAlpha = MAX_ALPHA;
    /** Switch 判断是否在拖动 */
    private boolean mIsScrolled =false;
    
    public SlideSwitchView(Context context) {
        this(context, null);
    }

    public SlideSwitchView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public SlideSwitchView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    /**
     * 初始化相关资源
     */
    public void init() {
        mSwitchThumbPressed = BitmapFactory.decodeResource(getResources(),R.drawable.checkswitch_btn_pressed);
        mSwitchThumbNormal = BitmapFactory.decodeResource(getResources(),R.drawable.checkswitch_btn_unpressed);
        mSwitchBottom = BitmapFactory.decodeResource(getResources(),R.drawable.checkswitch_bottom);
        mSwitchFrame = BitmapFactory.decodeResource(getResources(),R.drawable.checkswitch_frame);
        mSwitchMask = BitmapFactory.decodeResource(getResources(),R.drawable.checkswitch_mask);
        mSwitchThumb = mSwitchThumbNormal;
        mMoveLength = mSwitchBottom.getWidth() - mSwitchFrame.getWidth();
        //绘制区域大小
        mDest = new Rect(0, 0, mSwitchFrame.getWidth(),mSwitchFrame.getHeight());
        mSrc = new Rect();
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setAlpha(255);
        //mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO Auto-generated method stub
        setMeasuredDimension(mSwitchFrame.getWidth(), mSwitchFrame.getHeight());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);
        if (mMoveDeltX > 0 || mMoveDeltX == 0 && mSwitchOn) {
            if (mSrc != null) {
                mSrc.set(mMoveLength - mMoveDeltX, 0, mSwitchBottom.getWidth()
                        - mMoveDeltX, mSwitchFrame.getHeight());
            }
        } else if (mMoveDeltX < 0 || mMoveDeltX == 0 && !mSwitchOn) {
            if (mSrc != null) {
                mSrc.set(-mMoveDeltX, 0, mSwitchFrame.getWidth() - mMoveDeltX,
                        mSwitchFrame.getHeight());
            }
        }
        Log.d("mAlpha", "mAlpha:" + mAlpha);
        //绘制一个不透明矩形 为白色 和黑色底衬 成灰色
        canvas.saveLayerAlpha(new RectF(mDest), mAlpha, Canvas.MATRIX_SAVE_FLAG
                | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
                | Canvas.FULL_COLOR_LAYER_SAVE_FLAG
                | Canvas.CLIP_TO_LAYER_SAVE_FLAG);
        canvas.drawBitmap(mSwitchBottom, mSrc, mDest, null);
        canvas.drawBitmap(mSwitchThumb, mSrc, mDest, null);
        canvas.drawBitmap(mSwitchFrame, 0, 0, null);
        canvas.drawBitmap(mSwitchMask, 0, 0, mPaint);
        canvas.restore();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // TODO Auto-generated method stub
        //如果Enabled属性设定为true,触摸效果才有效
        if(!mEnabled){
            return true;
        }
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mSwitchThumb = mSwitchThumbPressed;
            mLastX = event.getX();
            break;
        case MotionEvent.ACTION_MOVE:
            mCurrentX = event.getX();
            mMoveDeltX = (int) (mCurrentX - mLastX);
            if(mMoveDeltX > 10){
                //设置了10这个误差距离，可以更好的实现点击效果
                mIsScrolled = true;
            }
            // 如果开关开着向左滑动，或者开关关着向右滑动（这时候是不需要处理的）
            if ((mSwitchOn && mMoveDeltX < 0) || (!mSwitchOn && mMoveDeltX > 0)) {
                mFlag = true;
                mMoveDeltX = 0;
            }

            if (Math.abs(mMoveDeltX) > mMoveLength) {
                mMoveDeltX = mMoveDeltX > 0 ? mMoveLength : -mMoveLength;
            }
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
            mSwitchThumb = mSwitchThumbNormal;
            //如果没有滑动过，就看作一次点击事件
            if(!mIsScrolled){
                mMoveDeltX = mSwitchOn ? mMoveLength : -mMoveLength;
                mSwitchOn = !mSwitchOn;
                if (switchListener != null) {
                    switchListener.onSwitchChange(this, mSwitchOn);
                }
                invalidate();
                mMoveDeltX = 0;
                break;
            }
            mIsScrolled = false;
            if (Math.abs(mMoveDeltX) > 0 && Math.abs(mMoveDeltX) < mMoveLength / 2) {
                mMoveDeltX = 0;
                invalidate();
            } else if (Math.abs(mMoveDeltX) > mMoveLength / 2
                    && Math.abs(mMoveDeltX) <= mMoveLength) {
                mMoveDeltX = mMoveDeltX > 0 ? mMoveLength : -mMoveLength;
                mSwitchOn = !mSwitchOn;
                if (switchListener != null) {
                    switchListener.onSwitchChange(this, mSwitchOn);
                }
                invalidate();
                mMoveDeltX = 0;
            } else if (mMoveDeltX == 0 && mFlag) {
                // 这时候得到的是不需要进行处理的，因为已经move过了
                mMoveDeltX = 0;
                mFlag = false;
            }
        default:
            break;
        }
        invalidate();
        return true;
    }
    /** 
     * 设置 switch 状态监听 
     * */
    public void setOnChangeListener(OnSwitchChangedListener listener) {
        switchListener = listener;
    }
    /** 
     * switch 开关监听接口
     *  */
    public interface OnSwitchChangedListener{
        public void onSwitchChange(SlideSwitchView switchView, boolean isChecked);
    }
    
    @Override
    public void setEnabled(boolean enabled) {
        // TODO Auto-generated method stub
        mEnabled = enabled;
        mAlpha = enabled ? MAX_ALPHA : MAX_ALPHA/2;
        Log.d("enabled",enabled ? "true": "false");
        super.setEnabled(enabled);
        invalidate();
    }
    
    /** 自动判断切换至相反的属性 : true -->false ;false -->true */
    public void toggle() {
        setChecked(!mSwitchOn);
    }
    
    /** 设置选中的状态（选中:true   非选中: false） */
    public void setChecked(boolean checked) {
        mSwitchOn = checked;
        invalidate();
    }
}