Andriod實現刮刮卡的效果

思想：

將一個View設計成多層，內層（包括中獎信息）和外層（用于刮獎），外層的圖層用Canvas與一個Bitmap關聯，用這個關聯的Bitmap來處理手勢的滑動，類似于刮獎的動作。

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.PorterDuff;

import android.graphics.PorterDuffXfermode;

import android.util.AttributeSet;

import android.view.MotionEvent;

import android.view.View;

/**

Created by Administrator on 2015/7/29. 
*/

public class GuaView extends View {

 private Path mPath;

 private Paint mInnerPaint;  //內層圖層Paint

 private Paint mOuterPaint;  //外層圖層Paint

 private Bitmap mGuaBitmap;  //用于處理刮獎的Bitmap

 private Bitmap mOuterBitmap;  //外層圖層Bitmap

 private Canvas mCanvas;
private int mWidth, mHeight;
private float mLastX;

 private float mLastY;
private String mText;
public GuaView(Context context, AttributeSet attrs) {

 super(context, attrs);  
 init();  

}
private void init() {

 mPath = new Path();  
 mOuterPaint = new Paint();  
 mInnerPaint = new Paint();  

 //創建外層圖層  
 mOuterBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.guaguaka).copy(Bitmap.Config.ARGB_8888, true);  
 mText = "¥500";  

}
@Override

 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

 super.onMeasure(widthMeasureSpec, heightMeasureSpec);  

 mWidth = mOuterBitmap.getWidth();  
 mHeight = mOuterBitmap.getHeight();  

 //創建內層圖層  
 mGuaBitmap = Bitmap.createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);  
 mCanvas = new Canvas(mGuaBitmap);  
 mCanvas.drawBitmap(mOuterBitmap, 0, 0, null); //將mOuterBitmap畫到mCanvas上，與mGuaBitmap關聯  

 setOuterPaint();  
 setInnerPaint();  

}
private void setInnerPaint() {

 mInnerPaint.setColor(Color.RED);  
 mInnerPaint.setStyle(Paint.Style.STROKE);  
 mInnerPaint.setStrokeCap(Paint.Cap.ROUND);  
 mInnerPaint.setStrokeJoin(Paint.Join.ROUND);  
 mInnerPaint.setAntiAlias(true);  
 mInnerPaint.setDither(true); //防抖  
 mInnerPaint.setStrokeWidth(5);  
 mInnerPaint.setTextSize(100);  
 mInnerPaint.setTextAlign(Paint.Align.CENTER);  

}
private void setOuterPaint() {

 mOuterPaint.setColor(Color.GREEN);  
 mOuterPaint.setStyle(Paint.Style.STROKE);  
 mOuterPaint.setStrokeCap(Paint.Cap.ROUND);  
 mOuterPaint.setStrokeJoin(Paint.Join.ROUND);  
 mOuterPaint.setAntiAlias(true);  
 mOuterPaint.setDither(true); //防抖  
 mOuterPaint.setStrokeWidth(20);  

}
@Override  //Path

 public boolean onTouchEvent(MotionEvent event) {

 float x = event.getX();  
 float y = event.getY();  
 switch (event.getAction()) {  
     case MotionEvent.ACTION_DOWN:  
         mLastX = x;  
         mLastY = y;  
         mPath.moveTo(x, y);  
         break;  
     case MotionEvent.ACTION_MOVE:  
         float deltaX = Math.abs(x - mLastX);  
         float deltaY = Math.abs(y - mLastY);  
         if (deltaX > 5 || deltaY > 5) {  
             mPath.lineTo(x, y);  
         }  
         mLastX = x;  
         mLastY = y;  
         break;  
     case MotionEvent.ACTION_UP:  
         break;  
 }  
 invalidate();  
 return true;  

}
@Override

 protected void onDraw(Canvas canvas) {

 super.onDraw(canvas);  

 canvas.drawColor(Color.parseColor("#bbbbbb")); //背景底色  灰色  
 canvas.drawText(mText, mWidth / 2, mHeight / 4 * 3, mInnerPaint); //繪制文本  
 canvas.drawBitmap(mGuaBitmap, 0, 0, null); //繪制外層Bitmap, 將mBitmap顯示在界面上  
 drawPath();  

}
private void drawPath() {

 //使用該mode：dst和src相交后， 只保留dst，且除去相交的部份  
 mOuterPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));  
 mCanvas.drawPath(mPath, mOuterPaint);  

}

}  </pre>