android 自定义滑动按钮

第一接触公司项目就让我画页面，而且还涉及到我最讨厌的自定义view  但是没办法，讨厌也必须要做啊，经过百度上资源的查找，终于写出了一个滑动控件。废话不多说，上代码。

package com.etong.cpms.widget;

import com.etong.cpms.activity.R;

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

public class WiperSwitch extends View implements OnTouchListener{  
    private Bitmap bg_on, bg_off, slipper_btn;  
    private String mOnText = "打开";
    private String mOffText = "关闭";
    /**
     * 按下时的x和当前的x
     */  
    private float downX, nowX;  
      
    /**
     * 记录用户是否在滑动
     */  
    private boolean onSlip = false;  
      
    /**
     * 当前的状态
     */  
    private boolean nowStatus = false;  
      
    /**
     * 监听接口
     */  
    private OnChangedListener listener;  
      
      
    public WiperSwitch(Context context) {  
        super(context);  
        init();  
    }  
 
    public WiperSwitch(Context context, AttributeSet attrs) {  
        super(context, attrs);  
        init();  
    }  
      
    public void init(){  
        //载入图片资源  
        bg_on = BitmapFactory.decodeResource(getResources(), R.drawable.switch_bkg_switch1);  
        bg_off = BitmapFactory.decodeResource(getResources(), R.drawable.switch_bkg_switch1);  
        slipper_btn = BitmapFactory.decodeResource(getResources(), R.drawable.switch_btn_slip1);  
        setOnTouchListener(this);  
    }  
      
    protected void onDraw(Canvas canvas) {  
        super.onDraw(canvas);  
        Matrix matrix = new Matrix();  
        Paint paint = new Paint();  
        float x = 0;  
          
        //根据nowX设置背景，开或者关状态  
        if (nowX < (bg_on.getWidth()/2)){  
              canvas.drawBitmap(bg_off, matrix, paint);//画出关闭时的背景
              paint.setColor(Color.WHITE);
              paint.setFakeBoldText(true);
              paint.setTextSize(40);
              canvas.drawText(mOffText, (bg_off.getWidth()-slipper_btn.getWidth())/2, (bg_off.getHeight()+30)/2, paint);
        }else{  
            canvas.drawBitmap(bg_on, matrix, paint);//画出打开时的背景   
            canvas.drawBitmap(bg_on, matrix, paint);//画出打开时的背景   
            paint.setColor(Color.WHITE);
            paint.setFakeBoldText(true);
            paint.setTextSize(40);
            canvas.drawText(mOnText,(bg_on.getWidth()-slipper_btn.getWidth())/2, (bg_on.getHeight()+30)/2, paint);
        }  
          
        if (onSlip) {//是否是在滑动状态,    
            if(nowX >= bg_on.getWidth())//是否划出指定范围,不能让滑块跑到外头,必须做这个判断  
                x = bg_on.getWidth() - slipper_btn.getWidth()/2;//减去滑块1/2的长度  
            else  
                x = nowX - slipper_btn.getWidth()/2;  
        }else {  
            if(nowStatus){//根据当前的状态设置滑块的x值  
                x = bg_on.getWidth() - slipper_btn.getWidth();  
            }else{  
                x = 0;  
            }  
        }  
          
        //对滑块滑动进行异常处理，不能让滑块出界  
        if (x < 0 ){  
            x = 0;  
        }  
        else if(x > bg_on.getWidth() - slipper_btn.getWidth()){  
            x = bg_on.getWidth() - slipper_btn.getWidth();  
        }  
          
        //画出滑块  
        canvas.drawBitmap(slipper_btn, x , 0, paint);   
    }  
 
    @Override  
    public boolean onTouch(View v, MotionEvent event) {  
        switch(event.getAction()){  
        case MotionEvent.ACTION_DOWN:{  
            if (event.getX() > bg_off.getWidth() || event.getY() > bg_off.getHeight()){  
                return false;  
            }else{  
                onSlip = true;  
                downX = event.getX();  
                nowX = downX;  
            }  
            break;  
        }  
        case MotionEvent.ACTION_MOVE:{  
            nowX = event.getX();  
            break;  
        }  
        case MotionEvent.ACTION_UP:{  
            onSlip = false;  
            if(event.getX() >= (bg_on.getWidth()/2)){  
                nowStatus = true;  
                nowX = bg_on.getWidth() - slipper_btn.getWidth();  
            }else{  
                nowStatus = false;  
                nowX = 0;  
            }  
              
            if(listener != null){  
                listener.OnChanged(WiperSwitch.this, nowStatus);  
            }  
            break;  
        }  
        }  
        //刷新界面  
        invalidate();  
        return true;  
    }  
      
      
      
    /**
     * 为WiperSwitch设置一个监听，供外部调用的方法
     * @param listener
     */  
    public void setOnChangedListener(OnChangedListener listener){  
        this.listener = listener;  
    }  
      
    /**
     * 设置滑动开关的初始状态，供外部调用
     * @param checked
     */  
    public void setChecked(boolean checked){  
        if(checked){  
            nowX = bg_off.getWidth();  
        }else{  
            nowX = 0;
        }  
        nowStatus = checked;  
    }  
    /**
     * 回调接口
     * @author len
     *
     */  
    public interface OnChangedListener {  
        public void OnChanged(WiperSwitch wiperSwitch, boolean checkState);  
    }  
 
 
}