滑动开关控件

public class SlidButton extends View implements OnTouchListener {  
  
    private boolean nowChoose = false;// 记录当前按钮是否打开，true为打开，false为关闭  
    private boolean onSlip = false;// 记录用户是否在滑动  
    private float downX, nowX; // 按下时的x，当前的x  
    private Rect btn_on, btn_off;// 打开和关闭状态下，游标的Rect  
  
    private boolean isChgLsnOn = false;//是否设置监听  
    private OnChangedListener changedLis;  
  
    private Bitmap bg_on, bg_off, slip_btn;  
  
    public SlidButton(Context context, AttributeSet attrs) {  
        super(context, attrs);  
        init();  
    }  
  
    public SlidButton(Context context) {  
        super(context);  
        init();  
    }  
  
       @Override  
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  
        // TODO Auto-generated method stub  
        setMeasuredDimension(bg_on.getWidth(), bg_on.getHeight());  
    }  
  
    
  
    private void init() {  
        // 载入图片资源  
        bg_on = BitmapFactory.decodeResource(getResources(),  
                R.drawable.sild_bg_on);  
        bg_off = BitmapFactory.decodeResource(getResources(),  
                R.drawable.sild_bg_off);  
        slip_btn = BitmapFactory.decodeResource(getResources(),  
                R.drawable.sild_btn);  
        // 获得需要的Rect数据  
        btn_on = new Rect(0, 0, slip_btn.getWidth(), slip_btn.getHeight());  
        btn_off = new Rect(bg_off.getWidth() - slip_btn.getWidth(), 0,  
                bg_off.getWidth(), slip_btn.getHeight());  
        setOnTouchListener(this);  
    }  
      
      
    @Override  
    protected void onDraw(Canvas canvas) {  
        // TODO Auto-generated method stub  
        super.onDraw(canvas);  
          
        Matrix matrix = new Matrix();  
        Paint paint = new Paint();  
        float x;  
          
        {  
            if (nowX<(bg_on.getWidth()/2)) //滑动到前半段与后半段的背景不同,在此做判断  
                canvas.drawBitmap(bg_off, matrix, paint);//画出关闭时的背景  
            else  
                canvas.drawBitmap(bg_on, matrix, paint);//画出打开时的背景   
                  
            if (onSlip) {//是否是在滑动状态,    
                if(nowX >= bg_on.getWidth())//是否划出指定范围,不能让游标跑到外头,必须做这个判断  
                    x = bg_on.getWidth() - slip_btn.getWidth()/2;//减去游标1/2的长度  
                else  
                    x = nowX - slip_btn.getWidth()/2;  
            }else {  
                if(nowChoose)//根据现在的开关状态设置画游标的位置   
                    x = btn_off.left;  
                else  
                    x = btn_on.left;  
            }  
              
            if (x < 0 ) //对游标位置进行异常判断..  
                x = 0;  
            else if(x > bg_on.getWidth() - slip_btn.getWidth())  
                x = bg_on.getWidth() - slip_btn.getWidth();  
              
            canvas.drawBitmap(slip_btn, x,0, paint);//画出游标.     
        }  
    }  
  
    @Override  
    public boolean onTouch(View v, MotionEvent event) {  
          
        switch (event.getAction()) {//根据动作来执行代码  
              
            case MotionEvent.ACTION_MOVE://滑动  
                nowX = event.getX();  
                break;  
            case MotionEvent.ACTION_DOWN://按下  
                if (event.getX() > bg_on.getWidth() || event.getY() > bg_on.getHeight())   
                    return false;  
                onSlip = true;  
                downX = event.getX();  
                nowX = downX;  
                break;  
            case MotionEvent.ACTION_UP://松开  
                onSlip = false;  
                boolean lastChoose = nowChoose;  
                if (event.getX() >= (bg_on.getWidth()/2))   
                    nowChoose = true;  
                else   
                    nowChoose = false;  
                if(isChgLsnOn && (lastChoose != nowChoose))//如果设置了监听器,就调用其方法.  
                    changedLis.OnChanged(nowChoose);  
                break;  
            default:  
                break;  
        }  
        invalidate();  
        return true;  
    }  
  
      
    public void SetOnChangedListener(OnChangedListener l){//设置监听器,当状态修改的时候  
        isChgLsnOn = true;  
        changedLis = l;  
    }  
      
    public interface OnChangedListener {  
        abstract void OnChanged(boolean checkState);  
    }  
}