问题
I’m trying to setup an onDrag Listener for a google map fragment, but can’t get the drag event to fire. Since the map doesn't support drag events directly, I'm trying to implement a drag listener for the View. I know about the onMarkerDrag event, but that does me no good since I'm not trying to move markers around.
The reason for trapping map drag events is twofold:
First to detect if the user has panned the map. If they haven't, I like to keep their location on the screen, and animate to their location if it's not on the map. If they have panned the map, I assume they know what they want to see and force the location on the screen. (this seems like something that should be included in the API)
The second reason for trapping is to allow users to draw lines and polygons on the map. I can do this with onTap events(adding points), but I'd like to be able to let them freehand it as well.
My code looks like this:
mainActivity:
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
setUpMapIfNeeded();
mMapView = findViewById(R.id.map);
myMapDragListener = new MapDragListener();
mMapView.setOnDragListener(myMapDragListener);
The Listener:
public class MapDragListener implements OnDragListener {
/**
*
*/
public MapDragListener() {
super();
say.logCat("MapDragListener: I'm ALIVE!!!!");
}
private AkamaiAnnounce say = new AkamaiAnnounce();
private boolean inDrag;
private boolean hasPanned=false;
@Override
public boolean onDrag(View v, DragEvent event) {
say.logCat("MapDragListener.onDrag: " + event.toString());
//String dotTAG = (String) getTag();
if (event.getLocalState() != this) {
return false;
}
boolean myResult = true;
int action = event.getAction();
float x = event.getX();
float y = event.getY();
switch (action) {
case DragEvent.ACTION_DRAG_STARTED:
inDrag = true;
break;
case DragEvent.ACTION_DRAG_LOCATION:
break;
case DragEvent.ACTION_DRAG_ENTERED:
break;
case DragEvent.ACTION_DRAG_EXITED:
break;
case DragEvent.ACTION_DROP:
myResult = false;
break;
case DragEvent.ACTION_DRAG_ENDED:
inDrag = false; // change color of original dot back
hasPanned=true;
break;
default:
myResult = false;
break;
}
return false;
//return myResult;
}
public boolean hasPanned() {
return hasPanned;
}
public void setHasPanned(boolean hasPanned) {
this.hasPanned = hasPanned;
}
}
The map works fine. The listener instantiates, but my onDrag event never fires. Any ideas?
回答1:
1) Create wrapper class:
public class MapWrapperLayout extends FrameLayout {
public interface OnDragListener {
public void onDrag(MotionEvent motionEvent);
}
private OnDragListener mOnDragListener;
public MapWrapperLayout(Context context) {
super(context);
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (mOnDragListener != null) {
mOnDragListener.onDrag(ev);
}
return super.dispatchTouchEvent(ev);
}
public void setOnDragListener(OnDragListener mOnDragListener) {
this.mOnDragListener = mOnDragListener;
}
}
2) Create subclass of MapFragment class:
public class CustomMapFragment extends SupportMapFragment {
private View mOriginalView;
private MapWrapperLayout mMapWrapperLayout;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
mOriginalView = super.onCreateView(inflater, container, savedInstanceState);
mMapWrapperLayout = new MapWrapperLayout(getActivity());
mMapWrapperLayout.addView(mOriginalView);
return mMapWrapperLayout;
}
@Override
public View getView() {
return mOriginalView;
}
public void setOnDragListener(MapWrapperLayout.OnDragListener onDragListener) {
mMapWrapperLayout.setOnDragListener(onDragListener);
}
3.1) Finally, in your activity:
// Google map init block
CustomMapFragment customMapFragment = ((CustomMapFragment) getSupportFragmentManager().findFragmentById(R.id.map));
customMapFragment.setOnDragListener(new MapWrapperLayout.OnDragListener() {
@Override
public void onDrag(MotionEvent motionEvent) {
Log.d("ON_DRAG", String.format("ME: %s", motionEvent));
// Handle motion event:
}
});
GoogleMap map = customMapFragment.getMap();
3.2) ... and in your layout:
<fragment android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:name="your.package.CustomMapFragment"/>
回答2:
To get drag event listener a fragment containing googleMap, one can use below method of google. We can get the target position of map.
googleMap.setOnCameraIdleListener(new GoogleMap.OnCameraIdleListener() {
@Override
public void onCameraIdle() {
Log.e(TAG,"==camera idle=="+ googleMap.getCameraPosition().target);
}
});
googleMap.setOnCameraMoveStartedListener(new GoogleMap.OnCameraMoveStartedListener() {
@Override
public void onCameraMoveStarted(int reason) {
if (reason ==REASON_GESTURE) {
isMaptouched=true;
Toast.makeText(getActivity(), "The user gestured on the map.",
Toast.LENGTH_SHORT).show();
} else if (reason ==REASON_API_ANIMATION) {
Toast.makeText(getActivity(), "The user tapped something on the map.",
Toast.LENGTH_SHORT).show();
} else if (reason ==REASON_DEVELOPER_ANIMATION) {
Toast.makeText(getActivity(), "The app moved the camera.",
Toast.LENGTH_SHORT).show();
}
}
});
回答3:
I solved it using the onCameraMoveCancelledListener:
mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
@Override
public void onMapClick(LatLng latLng) {
stopCamera=true;
}
});
mMap.setOnCameraMoveCanceledListener(new GoogleMap.OnCameraMoveCanceledListener() {
@Override
public void onCameraMoveCanceled() {
stopCamera = true;
}
});
回答4:
I did something like similar using a BehaviorSubject to tell if the map was dirty (moved by user)
storeMap.setOnCameraMoveStartedListener(new GoogleMap.OnCameraMoveStartedListener() {
@Override
public void onCameraMoveStarted(int reason) {
if (reason == REASON_GESTURE) {
mapIsDirty.onNext(true);
}
}
});
storeMap.setOnCameraIdleListener(new OnCameraIdleListener() {
@Override
public void onCameraIdle() {
if(mapIsDirty.getValue()) {
// Do happy things
mapIsDirty.onNext(false);
}
}
});
来源：https://stackoverflow.com/questions/17223155/creating-ondraglistener-for-google-map-v2-fragment