安卓：制作一个刮奖控件

1.创建自定义控件，如果要显示文字则继承TextView。

2.设置好画笔的颜色，粗细，空心还是实心，透明度，有无锯齿，等参数。

3.画笔还要设置交叉颜色的类型。

4.从资源图片获得覆盖奖品图片的图案。

package com.example.scratcharea;

import com.example.scratcharea.ScratchController.OnScratchListener;

import android.R.drawable;
import android.R.integer;
import android.app.ActionBar.LayoutParams;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.Toast;
import android.media.AudioManager;
import android.media.SoundPool;

public class ScratchController extends ImageView{

    private Context context;
    private Paint pen;
    private Path drawPath;
    private Paint bitmapPen;

    private Canvas canvas;
    private float mx,my;
    private SoundPool sp;
    int scratchSound;
    int streamId;
    boolean isplaying=false;
    OnScratchListener scratchListener;
    boolean canCalculate=false;
    
    private Bitmap maskbitmap;
    
    int picWidth;
    int picHeight;
    
    int maskWidth;
    int maskHeight;
    
    int picColorPixels;
    int maskColorPixels;
    
    public interface OnScratchListener{//事件监听接口
        void onScratch(int persent);
    }
    
    public void setOnScratchListener(OnScratchListener listener){
        this.scratchListener =  listener;
    }
    
    Handler scratchHandler = new Handler(){
        public void handleMessage(Message msg){
            if(scratchListener!=null){
                int persent = msg.arg1;
                scratchListener.onScratch(persent);
            }
        }
    };
    
    Runnable calMaskRunnable = new Runnable() {
        
        @Override
        public void run() {
            maskColorPixels=calColorPixels(maskbitmap);//计算所有有色像素的个数
    //    Log.i("calMaskRunnable","maskColorPixels:"+maskColorPixels);
        }
    };
    
    Runnable calPercentRunnable = new Runnable() {
        
        @Override
        public void run() {
            if(canCalculate){//计算后来的有色像素和初始有色像素的比值并增大100倍。。。
                int colorPixels=calColorPixels(maskbitmap);
            //    Log.i("calMaskRunnable","colorPixels: "+colorPixels);
                int percent =100-(int)((colorPixels*1.0/maskColorPixels)*100);
                Message msg= scratchHandler.obtainMessage();//从message pool中获取一个message 并且将message 的target属性指向改handler
                msg.arg1 =percent;//
                scratchHandler.sendMessage(msg);
            }
        }
    };
    
    private int calColorPixels(Bitmap bitmap){
        int colorPixels = 0;
        int w=bitmap.getWidth();
        int h=bitmap.getHeight();
        int arrLen = w*h;
        int [] pixels = new int [arrLen];
    //    Log.i("calColorPixels","w: "+w+" h: "+h);
        bitmap.getPixels(pixels, 0, w, 0, 0, w, h);//获取像素的点
        for(int i=0;i<arrLen;i++){
            if(pixels[i]!=0){
                colorPixels++;
            }
        }
        return colorPixels;
    }
    
    public ScratchController(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.context=context;
        TypedArray tArray = context.obtainStyledAttributes(attrs, R.styleable.ScratchArea);
        int len = tArray.length();
        for(int i=0;i<len;i++){
            if(R.styleable.ScratchArea_pic==tArray.getIndex(i)){
                int id = tArray.getResourceId(R.styleable.ScratchArea_pic, 0);
                if(id!=0){
                    setPic(id);
                }
            }
            if(R.styleable.ScratchArea_mask==tArray.getIndex(i)){
                int id = tArray.getResourceId(R.styleable.ScratchArea_mask, 0);
                if(id!=0){
                    if(id!=0){
                        setMask(id);
                    }
                }
            }
        }
        tArray.recycle();
    }
        
    public void setPic(int resId){
        this.setImageResource(resId);
        this.setScaleType(ImageView.ScaleType.FIT_XY);
//        ViewGroup.LayoutParams params = this.getLayoutParams();
//        picWidth = params.width;
//        picHeight = params.height;
    }
    
    @Override
    public void setLayoutParams(ViewGroup.LayoutParams params){
        super.setLayoutParams(params);
        picWidth = params.width;
        picHeight = params.height;
    }
    
    public void startInit(){
        init();
    }
    private void init() {
        pen = new Paint();
        pen.setAntiAlias(true);//抗锯齿
        //pen.setAlpha(220);//设置透明度
        pen.setDither(true);//设定是否使用图像抖动处理，会使绘制出来的图片颜色更加平滑和饱满，图像更加清晰  
        //pen.setColor(Color.WHITE);
        pen.setStyle(Paint.Style.STROKE);
        pen.setStrokeWidth(35);
        pen.setStrokeJoin(Paint.Join.ROUND);//前端是圆的
        pen.setStrokeCap(Paint.Cap.ROUND);//后端是圆的
        pen.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));//设置颜色交叉模式为清除
        
        bitmapPen=new Paint();
        drawPath = new Path();
        
        
        
        
        canvas = new Canvas(maskbitmap);
        //canvas.drawColor(maskColor);
        sp= new SoundPool(1,AudioManager.STREAM_SYSTEM,3);//
        scratchSound = sp.load(this.getContext(), R.raw.scratch3,1);
        
        canCalculate= false;
    }
    
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        
        this.canvas.drawPath(drawPath, pen);
        canvas.drawBitmap(maskbitmap, 0, 0, bitmapPen);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {//事件处理函数
        switch (event.getAction()){
        case MotionEvent.ACTION_DOWN:
            touchDown(event);
            //Toast.makeText(this.context, "touchDown", Toast.LENGTH_SHORT).show();
            break;
        case MotionEvent.ACTION_MOVE:
            touchMove(event);
            //Toast.makeText(this.context, "touchMove", Toast.LENGTH_SHORT).show();
            break;
        case MotionEvent.ACTION_UP:
            touchUp(event);
            break;
        default:
            break;
        }
        return true;
    }

    private void touchUp(MotionEvent event) {
        if(isplaying){
            sp.stop(streamId);
            isplaying = false;
        }
        canCalculate = true;
        new Thread(calPercentRunnable).start();
    }

    private void touchMove(MotionEvent event) {

    //Toast.makeText(this.context, "touchMove", Toast.LENGTH_SHORT).show();
        
        float preX=mx;
        float preY=my;
        mx = event.getX();
        my = event.getY();
        
        if(Math.abs(preX-mx)>1||Math.abs(preY-my)>1){
            
            float cx=(preX+mx)/2;
            float cy=(preY+my)/2;
            
            drawPath.quadTo(cx, cy, mx, my);//贝塞尔曲线平滑处理
            if(!isplaying)
              streamId = sp.play(scratchSound, 1, 1, 0, -1, (float)0.5);
            isplaying =true;
            invalidate();
        }
        
    }

    private void touchDown(MotionEvent event) {
        
    //    Toast.makeText(this.context, "touchDown", Toast.LENGTH_SHORT).show();
        mx=event.getX();
        my=event.getY();
        
        drawPath.reset();
        drawPath.moveTo(mx, my);
        
    }
    
    public void setMask(int mask){
        Resources res = getResources();
        maskbitmap = BitmapFactory.decodeResource(res, mask).copy(Bitmap.Config.ARGB_8888, true);
      // bitmap = Bitmap.createBitmap(480, 800, Config.ARGB_8888);
        int width = maskbitmap.getWidth();
        //Log.i("ScratchController",""+width);
        //Toast.makeText(this.context, width, Toast.LENGTH_LONG).show();
        int height = maskbitmap.getHeight();
        //Log.i("ScratchController","height:"+height);
    
        maskWidth=picWidth;
        //Log.i("ScratchController","maskWidth:"+maskWidth);
        maskHeight =picHeight;
        //Log.i("ScratchController","maskHeight:"+maskHeight);
        
        float scaleWidth = ((float)maskWidth)/width;
        float scaleHeight = ((float)maskHeight)/height;
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);//放缩变换
        maskbitmap = Bitmap.createBitmap(maskbitmap,0,0,width,height,matrix,true);//以maskbitmap为模板创建bitmap
        
        new Thread(calMaskRunnable).start();
    }

    
}