android.view.MotionEvent#getXPrecision ( )源码实例Demo

@Override
public boolean onTrackballEvent(MotionEvent event) {
    final int action = event.getActionMasked();
    if (action == MotionEvent.ACTION_DOWN) {
        // Advance color when the trackball button is pressed.
        advanceColor();
    }

    if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_MOVE) {
        final int N = event.getHistorySize();
        final float scaleX = event.getXPrecision() * TRACKBALL_SCALE;
        final float scaleY = event.getYPrecision() * TRACKBALL_SCALE;
        for (int i = 0; i < N; i++) {
            moveTrackball(event.getHistoricalX(i) * scaleX,
                    event.getHistoricalY(i) * scaleY);
        }
        moveTrackball(event.getX() * scaleX, event.getY() * scaleY);
    }
    return true;
}
 

private MotionEvent transformEvent(MotionEvent e, int headerPosition) {
    if (headerPosition == MATCHED_STICKIED_HEADER) {
        return e;
    }

    long downTime = e.getDownTime();
    long eventTime = e.getEventTime();
    int action = e.getAction();
    int pointerCount = e.getPointerCount();
    int[] pointerIds = getPointerIds(e);
    MotionEvent.PointerCoords[] pointerCoords = getPointerCoords(e);
    int metaState = e.getMetaState();
    float xPrecision = e.getXPrecision();
    float yPrecision = e.getYPrecision();
    int deviceId = e.getDeviceId();
    int edgeFlags = e.getEdgeFlags();
    int source = e.getSource();
    int flags = e.getFlags();

    View headerHolder = getChildAt(headerPosition);
    for (int i = 0; i < pointerCount;i++) {
        pointerCoords[i].y -= headerHolder.getTop();
    }
    MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
            pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
            yPrecision, deviceId, edgeFlags, source, flags);
    return n;
}
 

private static MotionEvent transformEventOld(MotionEvent e, Matrix m) {
    long downTime = e.getDownTime();
    long eventTime = e.getEventTime();
    int action = e.getAction();
    int pointerCount = e.getPointerCount();
    int[] pointerIds = getPointerIds(e);
    PointerCoords[] pointerCoords = getPointerCoords(e);
    int metaState = e.getMetaState();
    float xPrecision = e.getXPrecision();
    float yPrecision = e.getYPrecision();
    int deviceId = e.getDeviceId();
    int edgeFlags = e.getEdgeFlags();
    int source = e.getSource();
    int flags = e.getFlags();
    // Copy the x and y coordinates into an array, map them, and copy back.
    float[] xy = new float[pointerCoords.length * 2];
    for (int i = 0; i < pointerCount;i++) {
        xy[2 * i] = pointerCoords[i].x;
        xy[2 * i + 1] = pointerCoords[i].y;
    }
    m.mapPoints(xy);
    for (int i = 0; i < pointerCount;i++) {
        pointerCoords[i].x = xy[2 * i];
        pointerCoords[i].y = xy[2 * i + 1];
        pointerCoords[i].orientation = transformAngle(
                m, pointerCoords[i].orientation);
    }
    MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
            pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
            yPrecision, deviceId, edgeFlags, source, flags);
    return n;
}
 

private MotionEvent transformEvent(MotionEvent e, int headerPosition) {
    if (headerPosition == MATCHED_STICKIED_HEADER) {
        return e;
    }

    long downTime = e.getDownTime();
    long eventTime = e.getEventTime();
    int action = e.getAction();
    int pointerCount = e.getPointerCount();
    int[] pointerIds = getPointerIds(e);
    MotionEvent.PointerCoords[] pointerCoords = getPointerCoords(e);
    int metaState = e.getMetaState();
    float xPrecision = e.getXPrecision();
    float yPrecision = e.getYPrecision();
    int deviceId = e.getDeviceId();
    int edgeFlags = e.getEdgeFlags();
    int source = e.getSource();
    int flags = e.getFlags();

    View headerHolder = getChildAt(headerPosition);
    for (int i = 0; i < pointerCount;i++) {
        pointerCoords[i].y -= headerHolder.getTop();
    }
    MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
            pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
            yPrecision, deviceId, edgeFlags, source, flags);
    return n;
}
 

private MotionEvent transformEvent(MotionEvent e, int headerPosition) {
    if (headerPosition == MATCHED_STICKIED_HEADER) {
        return e;
    }

    long downTime = e.getDownTime();
    long eventTime = e.getEventTime();
    int action = e.getAction();
    int pointerCount = e.getPointerCount();
    int[] pointerIds = getPointerIds(e);
    MotionEvent.PointerCoords[] pointerCoords = getPointerCoords(e);
    int metaState = e.getMetaState();
    float xPrecision = e.getXPrecision();
    float yPrecision = e.getYPrecision();
    int deviceId = e.getDeviceId();
    int edgeFlags = e.getEdgeFlags();
    int source = e.getSource();
    int flags = e.getFlags();

    View headerHolder = getChildAt(headerPosition);
    for (int i = 0; i < pointerCount;i++) {
        pointerCoords[i].y -= headerHolder.getTop();
    }
    MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
            pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
            yPrecision, deviceId, edgeFlags, source, flags);
    return n;
}
 

@Override
public boolean onTrackballEvent(MotionEvent event)
{
	int action = event.getAction();
	switch (action)
	{
		case MotionEvent.ACTION_UP:
			setFollowingThroughContext(!isFollowing);
			break;
		case MotionEvent.ACTION_MOVE:
			if (!isFollowing)
			{
				int n = event.getHistorySize();
				final float scaleX = event.getXPrecision();
				final float scaleY = event.getYPrecision();
				int dx = (int) (-event.getX() * scaleX);
				int dy = (int) (-event.getY() * scaleY);
				for (int i = 0; i < n; i++)
				{
					dx += -event.getHistoricalX(i) * scaleX;
					dy += -event.getHistoricalY(i) * scaleY;
				}
				if (Math.abs(dx) > 0 || Math.abs(dy) > 0)
				{
					onDragFinished(dx, dy);
				}
			}
			break;
	}

	/*
	 * for (MapOverlay mo : this.overlays) if (mo.onTrackballEvent(event,
	 * this)) return true;
	 */

	return true;
}