Question

我的ViewModel类在Java中，而我的Activity类在Kotlin中。我收到错误

09-18 14：01：32.737 14082-14082 / com.meme.archcompwordlist E / AndroidRuntime：致命异常：主要过程： com.meme.archcompwordlist，PID：14082 java.lang.RuntimeException：无法开始活动 ComponentInfo {com.meme.archcompwordlist / com.meme.archcompwordlist.MainActivity}： java.lang.RuntimeException：无法创建类的实例 com.meme.archcompwordlist.WordViewModel 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2665）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2726）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1477）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886） com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）的原因：java.lang.RuntimeException：无法创建的实例 com.meme.archcompwordlist.WordViewModel类在android.arch.lifecycle.ViewModelProvider $ AndroidViewModelFactory.create（ViewModelProvider.java:207）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:134）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:102）在com.meme.archcompwordlist.MainActivity.onCreate（MainActivity.kt：37）在android.app.Activity.performCreate（Activity.java:6679）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1118）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2618）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2726）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1477）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）上由：java.lang.reflect.InvocationTargetException 在java.lang.reflect.Constructor.newInstance0（本地方法）在java.lang.reflect.Constructor.newInstance（Constructor.java:430）在android.arch.lifecycle.ViewModelProvider $ AndroidViewModelFactory.create（ViewModelProvider.java:199）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:134）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:102）在com.meme.archcompwordlist.MainActivity.onCreate（MainActivity.kt：37）在android.app.Activity.performCreate（Activity.java:6679）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1118）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2618）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2726）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1477）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）导致：java.lang.RuntimeException：找不到实现 com.meme.archcompwordlist.room.WordRoomDatabase。 WordRoomDatabase_Impl 不存在在android.arch.persistence.room.Room.getGeneratedImplementation（Room.java:93）在android.arch.persistence.room.RoomDatabase $ Builder.build（RoomDatabase.java:630）在com.meme.archcompwordlist.room.WordRoomDatabase.getRoomDatabase（WordRoomDatabase.java:22）在com.meme.archcompwordlist.WordRepository。（WordRepository.java:21）在com.meme.archcompwordlist.WordViewModel。（WordViewModel.java:22）在java.lang.reflect.Constructor.newInstance0（本地方法）在java.lang.reflect.Constructor.newInstance（Constructor.java:430）在android.arch.lifecycle.ViewModelProvider $ AndroidViewModelFactory.create（ViewModelProvider.java:199）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:134）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:102）在com.meme.archcompwordlist.MainActivity.onCreate（MainActivity.kt：37）在android.app.Activity.performCreate（Activity.java:6679）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1118）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2618）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2726）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1477）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）

这是我的AndroidViewModel类

public class WordViewModel extends AndroidViewModel {

    private WordRepository repository;

    private LiveData<List<WordEntity>> allWords;

    public WordViewModel(Application application){
        super(application);
        repository = new WordRepository(application);
        allWords = repository.getAllWords();
    }

    public LiveData<List<WordEntity>> getAllWords(){
        return allWords;
    }

    public void insert(WordEntity word){
        repository.insert(word);
    }

    public void deleteAllWords() {
        repository.deleteAllWords();
    }
}

这是我的活动课

class MainActivity : AppCompatActivity() {

    private lateinit var wordViewModel:WordViewModel
    private lateinit var newWord:EditText
    private lateinit var recyclerView:RecyclerView
    private lateinit var adapter:WordAdapter


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        adapter= WordAdapter()
        recyclerView= findViewById<RecyclerView>(R.id.wordList)
        recyclerView.adapter=adapter

        //establish a connection to the current ViewModel
        wordViewModel= ViewModelProviders.of(this).get(WordViewModel::class.java)

        newWord = findViewById<EditText>(R.id.insertWord);
        findViewById<Button>(R.id.submitWord).setOnClickListener {
             fun onClick(v:View?){
                if(!TextUtils.isEmpty(newWord.getText())){
                    wordViewModel.insert(WordEntity(newWord.getText().toString()))
                }
            }
        }
        findViewById<Button>(R.id.deleteWords).setOnClickListener{
            fun onClick(v:View?){
                wordViewModel.deleteAllWords()
            }
        }


        wordViewModel.getAllWords().observe(this,Observer<List<WordEntity>>(){
            fun onChanged(words:List<WordEntity>){
            adapter.setWords(words)
        }
        })

    }

}

有人可以帮助我确定我在做什么错吗？在远离Android的情况下，我想尝试使用Architecture Components。我还不清楚如何进行。

Answer 1

我遇到了同样的问题，并从此blog找到了解决方法。

您应将ViewModelProvider.AndroidViewModelFactory传递给ViewModelProvider，如下所示：

WordViewModel model = new ViewModelProvider(this, new ViewModelProvider.AndroidViewModelFactory(getApplication())).get(WordViewModel.class);

无法创建AndroidViewModel的子类的实例

1 个答案: