Question

我正在尝试使用android ViewModel和LiveData，但是当我想创建观察时出现错误。第一个参数给我一个错误：错误的第一个参数类型，它是期望Lifecycleowner。如果我尝试构建它：不兼容的类型：FragStat无法转换为LifecycleOwner 我正在使用构建工具27.0.1和支持库。

这是我的片段：

import android.arch.lifecycle.Observer;
import android.arch.lifecycle.ViewModelProviders;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;

import android.support.v7.widget.RecyclerView;
import android.util.Log;

import com.example.konem.pubgstat.Adapters.StatAdapter;
import com.example.konem.pubgstat.LocalStatViewModel;
import com.example.konem.pubgstat.Models.LocalStat;
import com.example.konem.pubgstat.R;
import com.example.konem.pubgstat.Utils.LocalData.AppDatabase;
import com.example.konem.pubgstat.Utils.UserManager;
import org.androidannotations.annotations.AfterViews;
import org.androidannotations.annotations.EFragment;
import org.androidannotations.annotations.ViewById;
import java.util.List;
import static android.content.ContentValues.TAG;

@EFragment(R.layout.fragment_frag_stat)
public class FragStat extends Fragment {
private List<LocalStat> localStats;
private StatAdapter statAdapter;
private AppDatabase appDatabase;
private UserManager userManager;


@ViewById
RecyclerView rvStats;

@AfterViews
void init() {
    appDatabase = AppDatabase.getAppDatabase(getActivity());
    userManager = new UserManager(getActivity());
    LocalStatViewModel mViewModel = 
    ViewModelProviders.of(this).get(LocalStatViewModel.class);


    statAdapter = new StatAdapter(localStats);

    rvStats.setLayoutManager(new LinearLayoutManager(getActivity()));
    rvStats.setAdapter(statAdapter);
    subscribetostats(mViewModel);
}

private void subscribetostats(LocalStatViewModel localStatViewModel) {
    localStatViewModel.getList().observe(this, new Observer<List<LocalStat>>() {
        @Override
        public void onChanged(@Nullable List<LocalStat> localStats) {

        }
    });
}

}

Answer 1

设置从DOA界面获取记录的返回类型为
LiveData<List<LocatStat>> getAllStats();

然后获取片段中的实时数据

LiveData<List<LocalStat> localStats;

最后在片段

中设置Livedata观察者

localStats.getList().observe(this, new Observer<List<LocalStat>>() {
    @Override
    public void onChanged(@Nullable List<LocalStat> localStats) {

        // Update UI

    }
});

Answer 2

所以经过几天尝试后我发现了问题。你必须在每个片段或活动中包含这几行，我认为是由appcombat实现但不是......

private LifecycleRegistry mLifecycleRegistry;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mLifecycleRegistry = new LifecycleRegistry(this);
    mLifecycleRegistry.markState(Lifecycle.State.CREATED);

}

@Override
public void onStart() {
    super.onStart();
    mLifecycleRegistry.markState(Lifecycle.State.STARTED);
}

@NonNull
@Override
public Lifecycle getLifecycle() {
    return mLifecycleRegistry;
}

ViewModel Observer的第一个参数是需要Lifecycleowner

2 个答案: