android上类似iphone上的开关按钮

public class SlipButton extends View {  
  
    private boolean nowChoose = false;//记录当前按钮是否打开,true为打开,flase为关闭  
    private boolean onSlip = false;//记录用户是否在滑动的变量  
    private float nowX;//按下时的x,当前的x
    private float downX;
    private float baseX;
    private OnChangedListener ChgLsn;  
    private Bitmap slip_btn; 
    private float centerX;
    
    private float yes_text_width;
    private float no_text_width;
    
    private int btnWdith;
    private String[] messages;
    
    private Paint paint;
      
    public SlipButton(Context context) {  
        super(context);   
        init();  
    }  
  
    public SlipButton(Context context, AttributeSet attrs) {  
        super(context, attrs);  
        init();  
    }  
  
    private void init() { 
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setColor(Color.BLACK);
        paint.setTextSize(14);
        setMessages(new String[]{"Yes", "No"});
    }
    
    public void setButtonBitmap(Bitmap bitmap) {
    	if (bitmap == null) {
    		return;
    	}
    	slip_btn = bitmap;
        btnWdith = slip_btn.getWidth() / 3;
        centerX = btnWdith / 2;
    }
    
    public void setTextColor(int color) {
    	paint.setColor(color);
    }
    
    public void setTextSize(int size) {
    	paint.setTextSize(size);
    }
    
    public void setMessages(String[] messages) {
    	this.messages = messages;
    	yes_text_width = paint.measureText(messages[0]);
        no_text_width = paint.measureText(messages[1]);
    }
    
    public void setStatusOn(boolean on) {
    	nowChoose = on;
    }
    
    public boolean getStatusOn() {
    	return nowChoose;
    }
    
    public void setOnChangedListener(OnChangedListener l) {
        ChgLsn = l;  
    }
      
    @Override  
    protected void onDraw(Canvas canvas) { 
        super.onDraw(canvas);
        if (slip_btn == null) {
    		return;
    	}
        
        float minX = centerX;
        float maxX = getMeasuredWidth() - centerX;
        
        if (onSlip) {
        	nowX = baseX - (downX - nowX);
        	nowX = Math.min(Math.max(minX, nowX), maxX);
        } else {
        	if (nowChoose) {
        		nowX = maxX;
        	} else {
        		nowX = minX;
        	}
        	baseX = nowX;
        }
	    canvas.drawBitmap(slip_btn, nowX - centerX - btnWdith, 0, paint);//画出游标.
	   
        int marginX1 = (int)(btnWdith - yes_text_width) / 2;
        canvas.drawText(messages[0], nowX - centerX - marginX1 - yes_text_width, 22, paint);
	    
        int marginX2 = (int)(btnWdith - no_text_width) / 2;
        canvas.drawText(messages[1], nowX + centerX + marginX2, 22, paint);
    }  
  
  
    @Override
	public boolean onTouchEvent(MotionEvent event) {
    	if (slip_btn == null) {
    		return false;
    	}
    	
        switch(event.getAction())//根据动作来执行代码  
        {  
        case MotionEvent.ACTION_MOVE://滑动 
        	nowX = event.getX();
        	float moveX = downX - nowX;
        	if (Math.abs(moveX) > 5) {
        		onSlip = true;
        	}
            break;  
        case MotionEvent.ACTION_DOWN://按下  
        	downX = event.getX();
            break;  
        case MotionEvent.ACTION_UP://松开  
        	boolean LastChoose = nowChoose;
        	if (onSlip) {
        		moveX = downX - event.getX();
        		if (nowChoose) {
        			if ((moveX > 0) && (moveX >= centerX))
        				nowChoose = !nowChoose;
        		} else {
        			if ((moveX < 0) && (Math.abs(moveX) >= centerX))
        				nowChoose = !nowChoose;
        		} 
        	} else {
        		nowChoose = !nowChoose;
        	}
            onSlip = false;
            if ((ChgLsn != null) && (LastChoose != nowChoose)) {
            	if (nowChoose) {
            		ChgLsn.onChanged(nowChoose, messages[0]);
            	} else {
            		ChgLsn.onChanged(nowChoose, messages[1]);
            	}
            }
            break;  
        default:
        	break; 
        }  
        invalidate();//重画控件  
        return true;
	}
    
    public interface OnChangedListener {
    	public void onChanged(boolean on, String value);
    }
}