我正在使用 Android Drag&Drop API,并尝试将拖动阴影的锚点设置为触摸发生的点View
。默认行为是将锚点放在中间View
.
我做了一些研究,看来这可以通过覆盖来完成onProvideShadowMetrics (Point shadowSize, Point shadowTouchPoint)方法中的DragShadowBuilder
班级。据我了解,如果我改变 x,y 坐标shadowTouchPoint
它应该修改拖动锚点的坐标。
我所做的就是延长DragShadowBuilder
像这样的类:
class EventDragShadowBuilder extends DragShadowBuilder {
int touchPointXCoord, touchPointYCoord;
public EventDragShadowBuilder() {
super();
}
public EventDragShadowBuilder(View view, int touchPointXCoord,
int touchPointYCoord) {
super(view);
this.touchPointXCoord = touchPointXCoord;
this.touchPointYCoord = touchPointYCoord;
}
@Override
public void onProvideShadowMetrics(Point shadowSize,
Point shadowTouchPoint) {
shadowTouchPoint.set(touchPointXCoord, touchPointYCoord);
super.onProvideShadowMetrics(shadowSize, shadowTouchPoint);
}
}
In the Fragment
在我使用拖放的地方,我创建了两个侦听器来启动拖动事件View
:
mEventLongClickListener = new OnLongClickListener() {
@Override
public boolean onLongClick(View view) {
EventDragShadowBuilder shadowBuilder = new EventDragShadowBuilder(
view, mEventTouchXCoord, mEventTouchYCoord);
view.startDrag(null, shadowBuilder, view, 0);
return true;
}
};
// We need this listener in order to get the corect coordinates for the
// drag shadow
mEventTouchListener = new OnTouchListener() {
@Override
public boolean onTouch(View view, MotionEvent event) {
final int action = event.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
mEventTouchXCoord = (int) event.getX();
mEventTouchYCoord = (int) event.getY();
break;
}
}
return false;
}
};
我设置了两个听众:
itemView.setOnLongClickListener(mEventLongClickListener);
itemView.setOnTouchListener(mEventTouchListener);
到这里一切都好。但是当我测试应用程序并开始拖动过程时,拖动阴影位于触摸点下方的中心。因此它使用默认行为。我尝试调试,我发现mEventTouchXCoord
and mEventTouchYCoord
设置正确。方法shadowTouchPoint.set(touchPointXCoord, touchPointYCoord);
获得正确的坐标,但仍然以阴影为中心。
我不知道我做错了什么。也许我误解了API。任何帮助或提示将不胜感激。