我有一个MVVM设置,其中有两个片段通过ViewModel进行交互。我的SourceFragment
正在更新VM中的两个MutableLiveData
LatLng。我的第二个是MapFragment
,其中我使用两个LatLng LiveData绘制了一条路线。活动启动时,两个片段都被加载。 SourceFragment更新LatLng。我需要等待地图加载,然后再请求绘制路线,并且我有第三个MutableLiveData
布尔值,一旦加载地图,我就对其进行更新。目前,我实现此目标的方法是通过为我的MutableLiveData
中的三个MapFragment
设置三个单独的viewModel观察器,并使用一组if语句来检查是否同时设置了所有三个MutableLiveData
。我感觉可以使用MediatorLiveData
之类的方法来更好地完成此操作,但是我还没有找到可以解决的示例。 MediatorLiveData
或其他适用于此处的内容吗?
我的源代码片段
viewModel.setPickupLocation(pickupLatLng);
viewModel.setDestinationLatLng(destinationLatLng());
我的地图片段
@Override
public void onActivityCreated(@NonNull Bundle savedInstanceState) {
Log.d(TAG, "onActivityCreated: called");
super.onActivityCreated(savedInstanceState);
getCustomerOrDriverViewModel();
}
private void initViewModels() {
viewModel.getPickupLocation().observe(getViewLifecycleOwner(), new Observer<LatLng>() {
@Override
public void onChanged(@NonNull LatLng pickupLocation) {
Log.d(TAG, "onChanged: from onActivityCreated: called for getPickupLocation");
if(viewModel.getMapReady().getValue() != null) {
if(viewModel.getMapReady().getValue()) {
resetRoute();
setSingleMarker(pickupLocation);
if(viewModel.getDestinationLatLng().getValue() != null) {
plotRoute(viewModel.getDestinationLatLng().getValue(), pickupLocation);
}
}
}
}
});
viewModel.getDestinationLatLng().observe(getViewLifecycleOwner(), new Observer<LatLng>() {
@Override
public void onChanged(@NonNull LatLng destinationLatLng) {
Log.d(TAG, "onChanged: from onActivityCreated: called for getPickupLocation");
if(viewModel.getMapReady().getValue() != null) {
if(viewModel.getMapReady().getValue()) {
resetRoute();
if(viewModel.getPickupLocation().getValue() != null) {
plotRoute(destinationLatLng, viewModel.getPickupLocation().getValue());
}
}
}
}
});
viewModel.getMapReady().observe(getViewLifecycleOwner(), new Observer<Boolean>() {
@Override
public void onChanged(@NonNull Boolean ready) {
Log.d(TAG, "onChanged: from onActivityCreated: called for getMapReady");
if(ready) {
if(viewModel.getPickupLocation().getValue() != null && viewModel.getDestinationLatLng().getValue() != null) {
Log.d(TAG, "onChanged: from onActivityCreated: called for getMapReady: plotting route");
resetRoute();
plotRoute(viewModel.getDestinationLatLng().getValue(), viewModel.getPickupLocation().getValue());
}
}
}
});
}
mMap.setOnMapLoadedCallback(new GoogleMap.OnMapLoadedCallback() {
@Override
public void onMapLoaded() {
viewModel.setMapReady(true);
}
});
我的ViewModel
private MutableLiveData<LatLng> pickupLocation = new MutableLiveData<>();
private MutableLiveData<LatLng> destinationLatLng = new MutableLiveData<>();
private MutableLiveData<Boolean> mapReady = new MutableLiveData<>();
public void setPickupLocation(LatLng input) {
Log.d(TAG, "setPickupLocation: ");
pickupLocation.setValue(input);
}
public void setDestinationLatLng(LatLng input) {
Log.d(TAG, "setPickupLocation: ");
destinationLatLng.setValue(input);
}
public void setMapReady(Boolean input) {
Log.d(TAG, "setPickupLocation: ");
mapReady.setValue(input);
}
public MutableLiveData<LatLng> getPickupLocation() {
Log.d(TAG, "getPickupLocation: ");
return pickupLocation;
}
public MutableLiveData<LatLng> getDestinationLatLng() {
Log.d(TAG, "getDestinationLatLng: ");
return destinationLatLng;
}
public MutableLiveData<Boolean> getMapReady() {
Log.d(TAG, "getMapReady: ");
return mapReady;
}
private void setupData(){
if(variable1 == null || variable2 == null || variable3 == null){
return;
}
plotRoute(xxxxxx);
}
然后在每个视图模型响应中调用setupData()代替三重嵌套的if语句检查