Question

我想在灰色方块位图上检测到手指的区域进行擦除但不起作用。

我用ic_launch作为图像显示一个位图，然后我在图像上显示一个灰色方形油漆，我可以将颜色修改为TRANSPARENT

有什么问题？谢谢

private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private Paint mPaint;

public CaseView(Context c) {
    super(c);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeWidth(40);


    mBitmap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < 100; j++) {
            mBitmap.setPixel(i, j, Color.GRAY);
        }

    }
    mCanvas = new Canvas(mBitmap);
    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(0, 0, oldw, oldh);

}

@Override
protected void onDraw(Canvas canvas) {

    canvas.drawRect(100, 100, 200, 200, mBitmapPaint);
    canvas.drawPath(mPath, mPaint);

    Bitmap _scratch = BitmapFactory.decodeResource(getResources(),
            R.drawable.ic_launcher);
    canvas.drawColor(Color.WHITE);

    // logo
    canvas.drawBitmap(_scratch, 0, 100, null);



    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < 100; j++) {
            if ((mX < 100 && mX >= 0) && (mY < 100 && mY >= 0)) {

                mBitmap.setPixel((int) mY,(int) mX,  Color.TRANSPARENT);
            }
        }

    }
    canvas.drawBitmap(mBitmap, 0, 100, mBitmapPaint);

    Bitmap mutableBitmap = Bitmap.createBitmap(_scratch.getWidth(),
            _scratch.getHeight(), Bitmap.Config.ARGB_8888);
    mutableBitmap.setPixel(50, 50, 124);
    canvas.drawBitmap(mutableBitmap, 0, 100, null);
    int pixelColor = mBitmap.getPixel(50, 50);
    int red = Color.red(pixelColor);
    int green = Color.green(pixelColor);
    Log.v("red", "red:" + red + " /green:" + green);


}


private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

private void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;
}

private void touch_move(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 touch_up() {
    mPath.lineTo(mX, mY);
    // commit the path to our offscreen
    mCanvas.drawPath(mPath, mPaint);
    // kill this so we don't double draw
    mPath.reset();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();
    Log.v("onTouchEvent", "x:" + x + "/y:" + y);

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touch_start(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_MOVE:
        touch_move(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        touch_up();
        invalidate();
        break;
    }
    return true;
}

Answer 1

对于绘图，您需要使用一个Paint类绘制路径。但是为了再次擦除，你必须在你的触摸坐标上绘制一条路径

mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

在 android-sdk 示例中，他们提供了一个 FingerPaint 类，可以很好地解释它

如何用手指擦除油漆

1 个答案: