类似刮奖

转载：http://blog.youkuaiyun.com/lmj623565791/article/details/40162163

其中Sa全称为Source alpha表示源图的Alpha通道；Sc全称为Source color表示源图的颜色；Da全称为Destination alpha表示目标图的Alpha通道；Dc全称为Destination color表示目标图的颜色，[…,..]前半部分计算的是结果图像的Alpha通道值，“,”后半部分计算的是结果图像的颜色值。图像混排后是依靠这两个值来重新计算ARGB值的

布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.administrator.testapplication.Main2Activity"
    >
  <!--    android:background="@mipmap/a" -->
  <com.example.administrator.testapplication.HappyCard
      android:layout_height="100dp"
      android:layout_width="300dp"
      ></com.example.administrator.testapplication.HappyCard>

</LinearLayout>

2

public class HappyCard extends View {
    /*绘制线条的Pain，用户手指绘制path*/
    private Paint mOutterPaint = new Paint();
    /*记录用户绘制的Path*/
    private Path mPath ;
    /*内存中创建的Canvas*/
    private Canvas mCanvas;
    /*mCanvas绘制内容在其上*/
    private Bitmap mBitmap;
    private int mLastX,mLastY;
    private Paint mBackPin = new Paint();
    private Rect mTextBound = new Rect();
    private String mText = "￥500,000,000";

    public HappyCard(Context context) {
        this(context,null,0);
    }

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

    public HappyCard(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mPath = new Path();
        setUpOuterPaint();
        setUpBackPaint();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int width = getMeasuredWidth();
        int height = getMeasuredHeight();

        //初始化bitmap
        mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
        //设置画笔//    mOutterPaint.setColor(Color.RED);
        mOutterPaint.setStyle(Paint.Style.FILL);
        mCanvas.drawRoundRect(new RectF(0, 0, width, height), 30, 30, mOutterPaint);//灰色层

      ;
        mCanvas.drawBitmap(BitmapFactory.decodeResource(getResources(),
                R.mipmap.s_title), null, new RectF(0, 0, width, height), null);//图片层

    }


    @Override
    protected void onDraw(Canvas canvas) {

  //     canvas.drawBitmap(mBitmap, 0, 0, null);
        //绘制奖金
        canvas.drawText(mText, getWidth() / 2 - mTextBound.width() / 2, getHeight() / 2 + mTextBound.height() / 2, mBackPin);

       if(!isComplete) {
           drawPath();
           canvas.drawBitmap(mBitmap, 0, 0, null);

       }
    }

    /*绘制细线*/
    private void drawPath() {
        mOutterPaint.setStyle(Paint.Style.STROKE);
        mOutterPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        mCanvas.drawPath(mPath,mOutterPaint);

    }
    private void setUpBackPaint(){
        mBackPin.setStyle(Paint.Style.FILL);
        mBackPin.setTextScaleX(2f);
        mBackPin.setColor(Color.DKGRAY);
        mBackPin.setTextSize(32);
        mBackPin.getTextBounds(mText, 0, mText.length(), mTextBound);
    }
    private void setUpOuterPaint(){
        mOutterPaint.setAntiAlias(true);
        mOutterPaint.setColor(Color.parseColor("#c0c0c0"));
        mOutterPaint.setDither(true);
        mOutterPaint.setStyle(Paint.Style.STROKE);
        mOutterPaint.setStrokeJoin(Paint.Join.ROUND);
        mOutterPaint.setStrokeCap(Paint.Cap.ROUND);
        mOutterPaint.setStrokeWidth(20); //设置画笔宽度
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int action = event.getAction();
        int x = (int) event.getX();
        int y = (int) event.getY();
        switch (action){
            case MotionEvent.ACTION_DOWN:
                mLastX = x;
                mLastY = y;
                mPath.moveTo(mLastX, mLastY);
                break;
            case MotionEvent.ACTION_MOVE:

                int dx = Math.abs(x - mLastX);
                int dy = Math.abs(y - mLastY);

                if(dx > 3 || dy >3)
                    mPath.lineTo(x, y);

                    mLastX = x;
                    mLastY = y;
                break;
            case MotionEvent.ACTION_UP:
                new Thread((mRunnable)).start();
                break;
        }
        invalidate();
        return true;
    }

    //统计擦除区域任务
    private  Runnable mRunnable = new Runnable() {
        private int[] mPixels;
        @Override
        public void run() {
            int w = getWidth();
            int h = getHeight();

            float wipeArea = 0;
            float totalArea = w*h;
            Bitmap bitmap = mBitmap;
            mPixels = new int[w*h];
            //拿到所有像素信息
            bitmap.getPixels(mPixels, 0, w, 0, 0, w, h);

            //遍历统计擦除的区域
            for (int i = 0; i < w; i++) {
                for (int j = 0; j < h; j++) {
                    int index = i+j*w;
                    if(mPixels[index] == 0){
                        wipeArea++;
                    }
                }
            }

        //根据所占比例，进行一些操作
            if(wipeArea>0&&totalArea>0){
                int percent   =(int)(wipeArea*100/totalArea);
                if(percent >70){
                    isComplete = true;
                    postInvalidate();
                }
            }
        }
    };
            boolean isComplete;
}