现在,LiveData非常受欢迎,如何使用viewmodel和LiveData将数据从活动发送到片段,反之亦然?请用编码示例解释.
解决方法:
在活动中
public class MyActivity extends AppCompatActivity {
Myviewmodel myviewmodel;
Handler handler;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
handler = new Handler();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.replace(R.id.container, MyFragment.newInstance())
.commitNow();
}
//Make View Holder Object
myviewmodel=viewmodelProviders.of(this).get(Myviewmodel.class);
myviewmodel.init();
myviewmodel.sendData("Hello kamy");
// Make thread to send data again
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printstacktrace();
}
handler.post(new Runnable() {
@Override
public void run() {
myviewmodel.sendData("How are You ?");
}
});
}
}).start();
}
}
在viewmodel类中
public class Myviewmodel extends viewmodel {
// Todo: Implement the viewmodel
private mutablelivedata<String> stringmutablelivedata;
public void init()
{
stringmutablelivedata=new mutablelivedata<>();
}
public void sendData(String msg)
{
stringmutablelivedata.setValue(msg);
}
public LiveData<String> getMessage()
{
return stringmutablelivedata;
}
}
在片段中
public class MyFragment extends Fragment {
private Myviewmodel mviewmodel;
private TextView textView;
public static MyFragment newInstance() {
return new MyFragment();
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
View view= inflater.inflate(R.layout.my_fragment, container, false);
textView=(TextView)view.findViewById(R.id.message);
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mviewmodel = viewmodelProviders.of(this).get(Myviewmodel.class);
viewmodelProviders.of(getActivity()).get(Myviewmodel.class).getMessage().observe(this, new Observer<String>() {
@Override
public void onChanged(@Nullable String message) {
textView.setText(message);
Toast.makeText(getContext(),message,Toast.LENGTH_SHORT).show();
}
});
}
}
片段xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/my"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.my.MyFragment">
<TextView
android:id="@+id/message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="MyFragment"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>