java - 如何在android Canvas 中使用Double Tap事件来保存当前图像

Question

我有一个扩展 View 的类，我可以将一个图像移动到另一个图像上，为此我使用两个位图图像一个放在另一个上，现在我想使用双击事件保存图像，但我不知道如何执行此操作....任何人都可以有一些想法或代码......

`公共(public)类 ShowCanvas 扩展 View {

Bitmap CanvasBitmap;
Bitmap ScaledBitmap;
Bitmap smallbitmap;
private static final int INVALID_POINTER_ID = -1;

private Drawable mImage;
private float mPosX;
private float mPosY;

private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;

public ShowCanvas(Context context) {

这个(上下文，空，0)； //TODO 自动生成构造函数 stub

    ScaledBitmap = DrawView.scaled;

    mImage = new BitmapDrawable(getResources(), Dress.bitmap);


    System.out.println("MImage" +mImage);

    mImage.setBounds(0, 0, mImage.getIntrinsicWidth(),
            mImage.getIntrinsicHeight());

}

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

public ShowCanvas(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

public void setBitmap(Bitmap bitmap) {
    // TODO Auto-generated method stub
    CanvasBitmap = bitmap;

    System.out.println("CanvasBitmap" + CanvasBitmap);

    int X = CanvasBitmap.getHeight();
    int Y = CanvasBitmap.getWidth();

    System.out.println("CanvasBitmap " + X + "\t" + Y);

}

@Override
public boolean isLongClickable() {
    // TODO Auto-generated method stub

    System.out.println("ISLongClickable");
    return super.isLongClickable();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    // Let the ScaleGestureDetector inspect all events.
    mScaleDetector.onTouchEvent(ev);




    final int action = ev.getAction();

    switch (action & MotionEvent.ACTION_MASK) {

    case MotionEvent.ACTION_DOWN: {
        final float x = ev.getX();
        final float y = ev.getY();

        mLastTouchX = x;
        mLastTouchY = y;
        mActivePointerId = ev.getPointerId(0);


        break;
    }

    case MotionEvent.ACTION_MOVE: {
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);

        // Only move if the ScaleGestureDetector isn't processing a
        // gesture.
        if (!mScaleDetector.isInProgress()) {
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            mPosX += dx;
            mPosY += dy;

            invalidate();
        }

        mLastTouchX = x;
        mLastTouchY = y;

        break;
    }

    case MotionEvent.ACTION_UP: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_CANCEL: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_POINTER_UP: {
        final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
        final int pointerId = ev.getPointerId(pointerIndex);
        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastTouchX = ev.getX(newPointerIndex);
            mLastTouchY = ev.getY(newPointerIndex);
            mActivePointerId = ev.getPointerId(newPointerIndex);
        }
        break;
    }
    }

    return true;
}

@Override
protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    Paint mpaint = new Paint();

    canvas.save();
    canvas.drawBitmap(ScaledBitmap, 0, 0, mpaint);
    Log.d("DEBUG", "X: " + mPosX + " Y: " + mPosY);
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor);
    mImage.draw(canvas);


    canvas.restore();

}

private class ScaleListener extends
        ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));

        invalidate();
        return true;
    }
}

}`

Answer 1

如果您的意思是双击，则必须使用 GestureDetector.OnDoubleTapListener。检查这个link

试试这个

public class MyView extends View {

GestureDetector gestureDetector;

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
            // creating new gesture detector
    gestureDetector = new GestureDetector(context, new GestureListener());
}

// skipping measure calculation and drawing

    // delegate the event to the gesture detector
@Override
public boolean onTouchEvent(MotionEvent e) {
    return gestureDetector.onTouchEvent(e);
}


private class GestureListener extends GestureDetector.SimpleOnGestureListener {

    @Override
    public boolean onDown(MotionEvent e) {
        return true;
    }
    // event when double tap occurs
    @Override
    public boolean onDoubleTap(MotionEvent e) {
        float x = e.getX();
        float y = e.getY();

        Log.d("Double Tap", "Tapped at: (" + x + "," + y + ")");

        return true;
    }
}
}