AppCompatActivity未观察到ViewModel

Question

我试图在EarthquakeActivity中一起使用ViewModel，但我一直收到这个错误：

Wrong 1st argument type. Found: 'com.example.android.quakereport.EarthquakeActivity', required: 'androidx.lifecycle.LifecycleOwner'

这是我尝试做的时候

mainViewModel.getEarthquakeData().observe(this, new Observer<List<Earthquake>>() {
@Override
public void onChanged(List<Earthquake> earthquakes) {
// do something
}
});

作为活动的this返回一个错误。

我在这里读到AppCompatActivity已经扩展了LifecycleOwner，这正是我正在使用的。这里怎么了？其他教程都没有这个问题。

我的EarthquakeActivity.java:

package com.example.android.quakereport;
import android.arch.lifecycle.ViewModelProviders;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
import POJO.Earthquake;
import POJO.RootEarthquakeResponse;
import androidx.lifecycle.Observer;
import retrofit2.Call;

public class EarthquakeActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private RecyclerView.Adapter adapter;
private LinearLayoutManager  layoutManager;
public static final String LOG_TAG = EarthquakeActivity.class.getName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.earthquake_activity);
// Create a fake list of earthquake locations.
final ArrayList<Earthquake> earthquakes = getEarthquakes();
setupRecyclerView(earthquakes); // set up recycler view
MainViewModel mainViewModel = ViewModelProviders.of(this).get(MainViewModel.class);
mainViewModel.getEarthquakeData().observe(this, new Observer<List<Earthquake>>() {
@Override
public void onChanged(List<Earthquake> earthquakes) {
// do something
}
});
}
private void setupRecyclerView(ArrayList<Earthquake> earthquakes){
// set up recyclerview
}
}

我的主视图模型：

package com.example.android.quakereport;
import android.app.Application;
import android.arch.lifecycle.AndroidViewModel;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;
import POJO.Earthquake;
import POJO.Feature;
import POJO.RootEarthquakeResponse;
import androidx.annotation.NonNull;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
public class MainViewModel extends AndroidViewModel {
private MutableLiveData<List<Earthquake>> earthquakeLiveData;
private String LOG_TAG = MainViewModel.class.getName();
public MainViewModel(@NonNull Application application) {
super(application);
//        earthquakeLiveData = new EarthquakeLiveData();
}
public LiveData<List<Earthquake>> getEarthquakeData(){
if (earthquakeLiveData == null){
earthquakeLiveData = new MutableLiveData<>();
loadEarthquakes();
}
return earthquakeLiveData;
}
private void loadEarthquakes(){
EarthquakeService earthquakeService = EarthquakeServiceGenerator.createService(EarthquakeService.class);
Call<RootEarthquakeResponse> call = earthquakeService.getEarthquakes("geojson", "time", 6, 10);
call.enqueue(new Callback<RootEarthquakeResponse>() {
@Override
public void onResponse(Call<RootEarthquakeResponse> call, Response<RootEarthquakeResponse> response) {
List<Earthquake> earthquakes = new ArrayList<>();
for (Feature f: response.body().getFeatures()) {
earthquakes.add(f.getEarthquake());
}
earthquakeLiveData.setValue(earthquakes);
Log.d(LOG_TAG, "Successful!");
Log.d(LOG_TAG, response.body().toString());
}
@Override
public void onFailure(Call<RootEarthquakeResponse> call, Throwable t) {
Log.e(LOG_TAG, call.request().toString()); // check request if failed
Log.e(LOG_TAG, t.toString()); // check error
}
});
}
}

以下是我的等级依赖关系：

implementation fileTree(dir: 'libs', include: ['*.jar'])
testImplementation 'junit:junit:4.12'
implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.android.support:recyclerview-v7:26.1.0'
implementation 'com.squareup.retrofit2:retrofit:2.5.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation 'com.squareup.okhttp3:logging-interceptor:3.9.1'
implementation "androidx.lifecycle:lifecycle-viewmodel:2.0.0" // use -ktx for Kotlin
// alternatively - just LiveData
implementation "androidx.lifecycle:lifecycle-livedata:2.0.0"
implementation "android.arch.lifecycle:extensions:1.1.1"

我需要处理覆盖生命周期吗？还是我的依赖关系出了问题？

Answer 1

您正在使用AndroidX库中的ViewModel，同时也在使用AppCompatActivity的支持库。

将您的支持库迁移到AndroidX以解决您的问题。