android - 可缩放 ListView 不滚动

Question

我有一个问题:我的自定义 ListView 在缩放前不滚动。缩放按预期工作。我该如何解决这个问题？

可缩放 ListView :

public class ZoomableListView extends ListView {

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
private boolean isPagerEnabled;
private static final int INVALID_POINTER_ID = -1;

// The ‘active pointer’ is the one currently moving our object.
private int mActivePointerId = INVALID_POINTER_ID;

private float mPosX;
private float mPosY;

private float mLastTouchX;
private float mLastTouchY;

// Pivot point for Scaling
static float gx = 0, gy = 0;

public ZoomableListView(Context context, AttributeSet attrs) {
super(context, attrs);
mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
}

public ZoomableListView(Context context) {
super(context);
mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
}

@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.translate(mPosX, mPosY);
canvas.scale(mScaleFactor, mScaleFactor);
canvas.restore();
}


@Override
protected void dispatchDraw(Canvas canvas) {
// Save the canvas to set the scaling factor returned from detector
canvas.save(Canvas.MATRIX_SAVE_FLAG);
if (mScaleFactor == 1.0f) {
    isPagerEnabled = true;
} else {
    isPagerEnabled = false;
}

if (mScaleFactor == 1.0f) {
    mPosX = 0.0f;
    mPosY = 0.0f;
}
canvas.translate(mPosX, mPosY);
canvas.scale(mScaleFactor, mScaleFactor);
super.dispatchDraw(canvas);
canvas.restore();
invalidate();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
mScaleDetector.onTouchEvent(ev);
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
    final float x = ev.getX();
    final float y = ev.getY();

    mLastTouchX = x;
    mLastTouchY = y;

    // Save the ID of this pointer
    mActivePointerId = ev.getPointerId(0);
    break;
}

case MotionEvent.ACTION_MOVE: {
    // Find the index of the active pointer and fetch its position
    final int pointerIndex = ev.findPointerIndex(mActivePointerId);
    final float x = ev.getX(pointerIndex);
    final float y = ev.getY(pointerIndex);

    final float dx = x - mLastTouchX;
    final float dy = y - mLastTouchY;

    mPosX += dx;
    mPosY += dy;

    mLastTouchX = x;
    mLastTouchY = y;

    invalidate();
    break;
}

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

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

case MotionEvent.ACTION_POINTER_UP: {
    // Extract the index of the pointer that left the touch sensor
    final int pointerIndex = (action & 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;
}

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(1.0f, Math.min(mScaleFactor, 3.0f));

    invalidate();
    return true;
}
}

这是自定义 ListView 的 XML:

<com.android.app.core.view.ZoomableListView
    android:id="@android:id/list"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginBottom="40dp"
    android:divider="@android:color/darker_gray"
    android:dividerHeight="1dp" >
</com.android.app.core.view.ZoomableListView>

感谢您的回答。

Answer 1

添加 super.onTouchEvent(ev);。我试了一下以确认它有效:

@Override
public boolean onTouchEvent(MotionEvent ev) {
    super.onTouchEvent(ev);
    ...