Java MediatorLiveData是否可以等待两个livedata也接收更新?
正如标题所说。我有两个livedata对象,它们从API获取一些数据。我想等待两个livedata在对其值执行某些操作之前完成数据的提取。 这就是我到目前为止所做的:Java MediatorLiveData是否可以等待两个livedata也接收更新?,java,android,retrofit,android-livedata,Java,Android,Retrofit,Android Livedata,正如标题所说。我有两个livedata对象,它们从API获取一些数据。我想等待两个livedata在对其值执行某些操作之前完成数据的提取。 这就是我到目前为止所做的: public class MainActivity extends AppCompatActivity implements View.OnClickListener { private Button myButt; private MainViewModel mvw; private TextView m
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Button myButt;
private MainViewModel mvw;
private TextView myView;
private MediatorLiveData data;
@Override
protected void onCreate(Bundle savedInstanceState) {
mvw = new ViewModelProvider(this).get(MainViewModel.class);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myButt = findViewById(R.id.button);
myView = findViewById(R.id.textview);
myButt.setOnClickListener(this);
data = new MediatorLiveData<>();
data.addSource(mvw.getAllOrders(), new Observer<Orders>() {
@Override
public void onChanged(Orders orders) {
data.setValue(orders);
}
});
data.addSource(mvw.getAllOrderRows(), new Observer<OrderRows>() {
@Override
public void onChanged(OrderRows orderRows) {
data.setValue(orderRows);
}
});
data.observe(this, new Observer<Orders>() {
@Override
public void onChanged(Orders order) {
myView.setText(mvw.extractDate(order));
//Here i want to manipulate order and orderrows
Log.i("livedata" , order.getOrders().toString());
}
});
}
@Override
public void onClick(View view) {
switch(view.getId()){
case R.id.button:
Log.i("button","clicked");
mvw.updateOrderData(); // calls for new values to be fetched
mvw.updateOrderRowData();
}
}
}
public类MainActivity扩展AppCompatActivity实现View.OnClickListener{
私人按钮;
私有主视图模型mvw;
私有文本视图myView;
私有数据;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
mvw=新的ViewModelProvider(this.get)(MainViewModel.class);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myButt=findViewById(R.id.按钮);
myView=findviewbyd(R.id.textview);
myButt.setOnClickListener(this);
data=新的MediatorLiveData();
data.addSource(mvw.getAllOrders(),new Observer()){
@凌驾
更改后的公共作废(订单){
数据设置值(订单);
}
});
data.addSource(mvw.getAllordErrors(),new Observer()){
@凌驾
更改后的公共void(OrderRows OrderRows){
data.setValue(orderRows);
}
});
data.observe(这个,新的观察者(){
@凌驾
更改后的公共作废(订单){
myView.setText(mvw.extractDate(order));
//这里我想处理order和orderrows
Log.i(“livedata”,order.getOrders().toString());
}
});
}
@凌驾
公共void onClick(视图){
开关(view.getId()){
案例R.id按钮:
Log.i(“按钮”,“点击”);
mvw.updateOrderData();//调用要获取的新值
mvw.updateOrderRowData();
}
}
}
问题是,我似乎只能听两个现场数据中的一个。如何等待两者都完成,然后对它们都执行一些操作?您可以编写一个MergedMediatorLiveData类,如下所示:
class MergedLiveData<T, K, S>(sourceA: LiveData<T>, sourceB: LiveData<K>, private val mergedCallback: (resultA: T?, resultB: K?) -> S) : MediatorLiveData<S>() {
private var resultA: T? = null
private var resultB: K? = null
init {
super.addSource(sourceA) {
resultA = it
value = mergedCallback(resultA, resultB)
}
super.addSource(sourceB) {
resultB = it
value = mergedCallback(resultA, resultB)
}
}
}
您可以按如下方式编写MergedMediatorLiveData类:
class MergedLiveData<T, K, S>(sourceA: LiveData<T>, sourceB: LiveData<K>, private val mergedCallback: (resultA: T?, resultB: K?) -> S) : MediatorLiveData<S>() {
private var resultA: T? = null
private var resultB: K? = null
init {
super.addSource(sourceA) {
resultA = it
value = mergedCallback(resultA, resultB)
}
super.addSource(sourceB) {
resultB = it
value = mergedCallback(resultA, resultB)
}
}
}