Android实现刮刮乐示例分析

微信公众号有很多都做刮刮乐的活动，本文就实现了刮刮乐的效果，具体代码如下：

首先要做一个类似橡皮擦的东西吧，然后才能把纸上的笔迹擦除
 

 
  public class Text_Rubbler extends TextView { 
    private float TOUCH_TOLERANCE; // 填充距离，使线条更自然，柔和,值越小，越柔和。 
    // private final int bGColor; 
    // 位图 
    private Bitmap mBitmap; 
    // 画布 
    private canvas mCanvas; 
    // 画笔 
    private Paint mPaint; 
    private Path mPath; 
    private float mX, mY; 
    private boolean isDraw = false; 
    public Text_Rubbler(Context context) { 
       
      super(context); 
    } 
    public Text_Rubbler(Context context, AttributeSet attrs, int defStyle) { 
      super(context, attrs, defStyle); 
      // bgColor = 
      // attrs.getAttributeIntValue("Http://schemas.Android.com/apk/res/android", 
      // "textColor", 0xFFFFFF); 
      // System.out.println("Color:"+bgColor); 
    } 
    public Text_Rubbler(Context context, AttributeSet attrs) { 
      super(context, attrs); 
      // bgColor = 
      // attrs.getAttributeIntValue("http://schemas.android.com/apk/res/android", 
      // "textColor", 0xFFFFFF); 
      // System.out.println(bgColor); 
      // System.out.println(attrs.getAttributeValue("http://schemas.android.com/apk/res/android", 
      // "layout_width")); 
    } 
    @Override 
    protected void onDraw(Canvas canvas) { 
      super.onDraw(canvas); 
      if (isDraw) { 
        mCanvas.drawPath(mPath, mPaint); 
        // mCanvas.drawPoint(mX, mY, mPaint); 
        canvas.drawBitmap(mBitmap, 0, 0, null); 
      } 
    } 
     
    public void beginRubbler(final int bgColor, final int paintStrokeWidth, 
        float touchTolerance) { 
      TOUCH_TOLERANCE = touchTolerance; 
      // 设置画笔 
      mPaint = new Paint(); 
      // mPaint.setAlpha(0); 
      // 画笔划过的痕迹就变成透明色了 
      mPaint.setColor(Color.BLACK); // 此处不能为透明色 
      mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT)); 
      // 或者 
      // mPaint.setAlpha(0); 
      // mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN)); 
      mPaint.setAntiAlias(true); 
      mPaint.setDither(true); 
      mPaint.setStyle(Paint.Style.STROKE); 
      mPaint.setStrokeJoin(Paint.Join.ROUND); // 前圆角 
      mPaint.setStrokeCap(Paint.Cap.ROUND); // 后圆角 
      mPaint.setStrokeWidth(paintStrokeWidth); // 笔宽 
      // 痕迹 
      mPath = new Path(); 
      ; 
      // 覆盖 
      // if (getLayoutParams().width == LayoutParams.FILL_PARENT) { 
      // 
      // } 
      mBitmap = Bitmap.createBitmap(getLayoutParams().width, 
          getLayoutParams().height, Config.ARGB_8888); 
      mCanvas = new Canvas(mBitmap); 
      mCanvas.drawColor(bgColor); 
      isDraw = true; 
    } 
    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
      if (!isDraw) { 
        return true; 
      } 
      switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: // 触点按下 
        // touchDown(event.getRawX(),event.getRawY()); 
        touchDown(event.getX(), event.getY()); 
        invalidate(); 
        break; 
      case MotionEvent.ACTION_MOVE: // 触点移动 
        touchMove(event.getX(), event.getY()); 
        invalidate(); 
        break; 
      case MotionEvent.ACTION_UP: // 触点弹起 
        touchUp(event.getX(), event.getY()); 
        invalidate(); 
        break; 
      default: 
        break; 
      } 
      return true; 
    } 
    private void touchDown(float x, float y) { 
      mPath.reset(); 
      mPath.moveTo(x, y); 
      mX = x; 
      mY = y; 
    } 
    private void touchMove(float x, float y) { 
      float dx = Math.abs(x - mX); 
      float dy = Math.abs(y - mY); 
      if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) { 
        mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2); 
        mX = x; 
        mY = y; 
      } 
    } 
    private void touchUp(float x, float y) { 
      mPath.lineTo(x, y); 
      mCanvas.drawPath(mPath, mPaint); 
      mPath.reset(); 
    } 
  } 

接下来就是使用橡皮檫擦除了
 

   
  public class RubblerAct extends Activity { 
    // 刮开后文字显示 
    private TextView tv_rubbler; 
    // 得到刮一刮的内容 
    private Sentence mSentence; 
    // 下一张 
    private TextView tv_next; 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      // setContentView(new Rubble(this,"谢谢惠顾",new Rect(100, 200, 
      // 300,250),2,1f,14)); 
      // ///////////////////////////////////////// 
      setContentView(R.layout.rubbler); 
      // 设置的颜色必须要有透明度。 
      ((Text_Rubbler) findViewById(R.id.rubbler)).beginRubbler(0xFFFFFFFF, 20, 
          1f);// 设置橡皮擦的宽度等 
      mSentence = new Sentence(); 
      // 随机初始化文字 
      tv_rubbler = (TextView) findViewById(R.id.rubbler); 
      String str = mSentence.getSentence(); 
      tv_rubbler.setText(str); 
      tv_next = (TextView) findViewById(R.id.tv_next); 
      // 点击下一步 
      tv_next.setOnClickListener(new OnClickListener() { 
        @Override 
        public void onClick(View v) { 
          // TODO Auto-generated method stub 
          String str = mSentence.getSentence(); 
          tv_rubbler.setText(str); 
          ((Text_Rubbler) findViewById(R.id.rubbler))// 初始化状态 
              .beginRubbler(0xFFFFFFFF, 20, 1f); 
        } 
      }); 
    } 
    class Rubble extends View { 
      private final int PAINT_STROKE_WIDTH; 
      private final float TOUCH_TOLERANCE; // 填充距离，使线条更自然，柔和,值越小，越柔和。 
      private final int TEXT_SIZE; 
      private Bitmap mBitmap; 
      // 画布 
      private Canvas mCanvas; 
      // 画笔 
      private Paint mPaint; 
      private Path mPath; 
      private float mX, mY; 
      private final int X, Y, W, H; 
      private final Rect touchRect; 
      public Rubble(Context context, String bgText, Rect rect, 
          int paintStrokeWidth, float touchTolerance, int textSize) { 
        super(context); 
        setFocusable(true); 
        touchRect = rect; 
        W = rect.right - rect.left; 
        H = rect.bottom - rect.top; 
        X = rect.left; 
        Y = rect.top; 
        TEXT_SIZE = textSize; 
        PAINT_STROKE_WIDTH = paintStrokeWidth; 
        TOUCH_TOLERANCE = touchTolerance; 
        setBackground(touchRect, bgText); 
        initDrowTools(); 
      } 
      private void setBackground(Rect rect, String bgText) { 
        DisplayMetrics dm = new DisplayMetrics(); 
        dm = this.getResources().getDisplayMetrics(); 
        Bitmap bitmap = Bitmap.createBitmap(dm.widthPixels, 
            dm.heightPixels, Config.ARGB_8888); 
        Canvas canvas = new Canvas(bitmap); 
        Paint paint = new Paint(); 
        paint.setColor(0x88000000); 
        // paint.setStyle(Style.STROKE); 
        // paint.setTextAlign(Align.CENTER); 
        paint.setTextSize(TEXT_SIZE); 
        // paint.setTextScaleX(1.5f); 
        canvas.drawColor(Color.WHITE); 
        // 画字的坐标不好控制 
        int x = rect.left 
            + (rect.right - rect.left - bgText.length() * TEXT_SIZE) 
            / 2; 
        int y = rect.top + (rect.bottom - rect.top - TEXT_SIZE) / 2; 
        // int y = 218+25; 
        canvas.drawText(bgText, x, y, paint); 
        Drawable drawable = new BitmapDrawable(bitmap); 
        setBackgroundDrawable(drawable); 
      } 
      private void initDrowTools() { 
        // 设置画笔 
        mPaint = new Paint(); 
        // mPaint.setAlpha(0); 
        // 画笔划过的痕迹就变成透明色了 
        mPaint.setColor(Color.BLACK); // 此处不能为透明色 
        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT)); 
        // 或者 
        // mPaint.setAlpha(0); 
        // mPaint.setXfermode(new 
        // PorterDuffXfermode(PorterDuff.Mode.DST_IN)); 
        mPaint.setAntiAlias(true); 
        mPaint.setDither(true); 
        mPaint.setStyle(Paint.Style.STROKE); 
        mPaint.setStrokeJoin(Paint.Join.ROUND); // 前圆角 
        mPaint.setStrokeCap(Paint.Cap.ROUND); // 后圆角 
        mPaint.setStrokeWidth(PAINT_STROKE_WIDTH); // 笔宽 
        // 痕迹 
        mPath = new Path(); 
        ; 
        // 覆盖 
        mBitmap = Bitmap.createBitmap(W, H, Config.ARGB_8888); 
        mCanvas = new Canvas(mBitmap); 
        mCanvas.drawColor(0x88000000); 
      } 
      @Override 
      protected void onDraw(Canvas canvas) { 
        super.onDraw(canvas); 
        mCanvas.drawPath(mPath, mPaint); 
        // mCanvas.drawPoint(mX, mY, mPaint); 
        canvas.drawBitmap(mBitmap, X, Y, null); 
      } 
      @Override 
      public boolean onTouchEvent(MotionEvent event) { 
        System.out.print("X--" + event.getX()); 
        System.out.println("Y--" + event.getY()); 
        if (!touchRect.contains((int) event.getX(), (int) event.getY())) { 
          return false; 
        } 
        switch (event.getAction()) { 
        // 触点按下 
        case MotionEvent.ACTION_DOWN: { 
          touchDown(event.getRawX(), event.getRawY()); 
          touchDown(event.getX() - touchRect.left, event.getY() 
              - touchRect.top); 
          invalidate(); 
          break; 
        } 
        case MotionEvent.ACTION_MOVE: // 触点移动 
          touchMove(event.getX() - touchRect.left, event.getY() 
              - touchRect.top); 
          invalidate(); 
          break; 
        case MotionEvent.ACTION_UP: // 触点弹起 
          touchUp(event.getX() - touchRect.left, event.getY() 
              - touchRect.top); 
          invalidate(); 
          break; 
        default: 
          break; 
        } 
        return true; 
      } 
      private void touchDown(float x, float y) { 
        mPath.reset(); 
        mPath.moveTo(x, y); 
        mX = x; 
        mY = y; 
      } 
      private void touchMove(float x, float y) { 
        float dx = Math.abs(x - mX); 
        float dy = Math.abs(y - mY); 
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) { 
          mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2); 
          mX = x; 
          mY = y; 
        } 
      } 
      private void touchUp(float x, float y) { 
        mPath.lineTo(x, y); 
        mCanvas.drawPath(mPath, mPaint); 
        mPath.reset(); 
      } 
    } 
     
    // 退出时间 
    private long exitTime = 0; 
    @Override 
    public boolean onKeyDown(int keyCode, KeyEvent event) { 
      if (keyCode == KeyEvent.KEYCODE_BACK 
          && event.getAction() == KeyEvent.ACTION_DOWN) { 
        if ((System.currentTimeMillis() - exitTime) > 2000) { 
          Toast.makeText(getApplicationContext(), "再按一次退出程序", 
              Toast.LENGTH_SHORT).show(); 
          exitTime = System.currentTimeMillis(); 
        } else { 
          finish(); 
          System.exit(0); 
        } 
        return true; 
      } 
      return super.onKeyDown(keyCode, event); 
    } 
  } 

实现效果如下：

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