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嗨，我正在尝试在 LinearLayout 中实现捏合缩放功能，我的第一次尝试是扩展线性布局并使用缩放手势检测器来检测捏合缩放手势，遵循android 开发人员博客的建议

我试图覆盖 onDraw 方法并使用画布设置缩放，但它根本不起作用，视图保持固定大小

这是我的自定义视图中的代码：

private static final int INVALID_POINTER_ID = -1;

private static final String TAG = "MyTag";

private float mScaleFactor = 1f;
private ScaleGestureDetector mScaleDetector;
private float mPosX;
private float mPosY;
private float mFocusX;
private float mFocusY;

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

private boolean mHandlingGesture = true;

public CrosswordGridLayout(Context context) {
    super(context);
    init();
}

public CrosswordGridLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public CrosswordGridLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
}

private void init() {
    setWillNotDraw(false);
    mScaleDetector = new ScaleGestureDetector(getContext(),
            new ScaleListener());
}

@Override
protected void onDraw(Canvas canvas) {
    Log.d(TAG, "onDraw");
    canvas.save();
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor, mFocusX, mFocusY);
    super.onDraw(canvas);
    canvas.restore();
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
    Log.d(TAG, "onTouchEvent");
    // Let the ScaleGestureDetector inspect all events.
    mHandlingGesture = 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;

            requestLayout();
        }

        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
public boolean onInterceptTouchEvent(MotionEvent ev) {
    return true;
}

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

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

        mFocusX = detector.getFocusX();
        mFocusY = detector.getFocusY();
        Log.d(TAG, "mScaleFactor=" + mScaleFactor);
        requestLayout();

        return true;
    }
}
4

1 回答 1

3

你canvas里面的操作dispatchDraw()不行吗onDraw()

protected void dispatchDraw(Canvas canvas) {
    Log.d(TAG, "dispatchDraw");
    canvas.save();
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor, mFocusX, mFocusY);
    super.dispatchDraw(canvas);
    canvas.restore();
}

该示例与您的代码之间的区别在于，在该示例中，它是缩放的简单视图，在您的情况下，它是 ViewGroup。

并且不要在使用requestLayout()中ScaleListener.onScale()使用invalidate()。

于 2012-09-04T15:22:33.970 回答