无法创建我的AndroidViewModel实例。

huangapple
go评论66阅读模式
英文:

Cannot create an instance of my AndroidViewModel

问题

这是我第一次使用Android和MVVM。

我遇到了这个错误：

E/AndroidRuntime: 致命异常: 主线程
    进程: com.ClementF.logged, PID: 11719
    java.lang.RuntimeException: 无法创建类 com.ClementF.logged.ActivityViewModel 的实例
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:275)
        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
        at com.ClementF.logged.ActivitySelectorFragment.onCreate(ActivitySelectorFragment.java:34)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:2684)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:270)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1173)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:442)
        at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2167)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1990)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1945)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1816)
        at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:297)
        at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:341)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:276)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:67)
        at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7556)
        at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:860)
        at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8601)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8559)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8547)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1641)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at androidx.viewpager2.widget.ViewPager2.onLayout(ViewPager2.java:527)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at com.google.android.material.appbar.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:148)
        at com.google.android.material.appbar.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:43)
        at com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1996)
        at androidx.coordinatorlayout.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:918)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
E/AndroidRuntime:     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:784)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3470)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2938)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:731)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     原因: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
        	... 79 more
     原因: java.lang.RuntimeException: 无法找到 com.ClementF.logged.ActivityDatabase 的实现。ActivityDatabase_Impl 不存在
        at androidx.room.Room.getGeneratedImplementation(Room.java:94)
        at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:952)
        at com.ClementF.logged.ActivityDatabase.getInstance(ActivityDatabase.java:24)
        at com.ClementF.logged.ActivityRepository.<init>(ActivityRepository.java:19)
        at com.ClementF.logged.ActivityViewModel.<init>(ActivityViewModel.java:18)
        	... 82 more

<details>
<summary>英文:</summary>

this is one of my first times using android and mvvm.

I get this error:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ClementF.logged, PID: 11719
java.lang.RuntimeException: Cannot create an instance of class com.ClementF.logged.ActivityViewModel
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:275)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.ClementF.logged.ActivitySelectorFragment.onCreate(ActivitySelectorFragment.java:34)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2684)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:270)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1173)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:442)
at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2167)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1990)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1945)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1816)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:297)
at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:341)
at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:276)
at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:67)
at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7556)
at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:860)
at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8601)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8559)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8547)
at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1641)
at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at androidx.viewpager2.widget.ViewPager2.onLayout(ViewPager2.java:527)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at com.google.android.material.appbar.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:148)
at com.google.android.material.appbar.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:43)
at com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1996)
at androidx.coordinatorlayout.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:918)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
E/AndroidRuntime: at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:784)
at android.view.View.layout(View.java:22844)
at android.view.ViewGroup.layout(ViewGroup.java:6389)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3470)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2938)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
at android.view.Choreographer.doCallbacks(Choreographer.java:796)
at android.view.Choreographer.doFrame(Choreographer.java:731)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
... 79 more
Caused by: java.lang.RuntimeException: cannot find implementation for com.ClementF.logged.ActivityDatabase. ActivityDatabase_Impl does not exist
at androidx.room.Room.getGeneratedImplementation(Room.java:94)
at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:952)
at com.ClementF.logged.ActivityDatabase.getInstance(ActivityDatabase.java:24)
at com.ClementF.logged.ActivityRepository.<init>(ActivityRepository.java:19)
at com.ClementF.logged.ActivityViewModel.<init>(ActivityViewModel.java:18)
... 82 more


This is my AndroidViewModel:

package com.ClementF.logged;

import android.app.Application;
import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;

import java.util.List;

public class ActivityViewModel extends AndroidViewModel {

private ActivityRepository activityRepository;
private LiveData&lt;List&lt;ActivityEntity&gt;&gt; activities;
public ActivityViewModel(@NonNull Application application) {
super(application);
activityRepository = new ActivityRepository(application);
activities = activityRepository.getAllActivities();
}
public void insert(ActivityEntity activity) {
activityRepository.insert(activity);
}
public void update(ActivityEntity activity) {
activityRepository.update(activity);
}
public void delete(ActivityEntity activity) {
activityRepository.delete(activity);
}
public LiveData&lt;List&lt;ActivityEntity&gt;&gt; getAllActivities() {
return activityRepository.getAllActivities();
}

}


And this is the fragment trying to access the ViewModel

package com.ClementF.logged;

import android.app.Application;
import android.os.Bundle;

import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProvider;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.List;

public class ActivitySelectorFragment extends Fragment {

private ActivityViewModel activityViewModel;
public ActivitySelectorFragment() {
// Required empty public constructor
}
public static ActivitySelectorFragment newInstance() {
return new ActivitySelectorFragment();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setup view model
activityViewModel = new ViewModelProvider(this).get(ActivityViewModel.class);
activityViewModel.getAllActivities().observe(this, new Observer&lt;List&lt;ActivityEntity&gt;&gt;() {
@Override
public void onChanged(List&lt;ActivityEntity&gt; activityEntities) {
// TODO: update recycler view
}
});
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_activity_selector, container, false);
}

}


I have tried passing a ViewModelProvider.AndroidViewModelFactory inside of the ViewModelProvider constructor however I get the same error.
Any ideas as to what I&#39;m doing wrong? Thank you so much!
If you need to know this is a fragment inside a ViewPager2 from my main_activity, I&#39;m using a tab layout.
Git repo: https://github.com/Teariest/Logged
</details>
# 答案1
**得分**: 0
```plaintext
发现实际上 ViewModel 没有错误。
将以下两行添加到您的 gradle 中，以便 Room 库可以编译 SQL 代码，处理注释并进行编译。
annotationProcessor "androidx.room:room-compiler:$room_version"
androidTestImplementation "androidx.room:room-testing:$room_version"
room_version 是从 Google 获取的最新版本。
然后同步 Gradle。
在 ActivityEntity 中为表添加 ColumnInfo，以便它可以在一个列中存储您的数据，您可以随意命名该列，我只是将其命名为 activity。
@ColumnInfo(name="activity")

注意：由于您要求只返回翻译好的内容，因此我仅提供了翻译后的文本，没有其他额外的内容。如果您有任何问题或需要进一步帮助，请随时问我。

英文:

Found out that there are no errors with ViewModel actually.

Add these two lines to your gradle so that Room library can compile the SQL codes,to handle the annotations and for compilation too.

annotationProcessor &quot;androidx.room:room-compiler:$room_version&quot;
androidTestImplementation &quot;androidx.room:room-testing:$room_version&quot;

无法创建我的AndroidViewModel实例。

room_version is what the latest version is available from Google

Then Sync Gradle

Add ColumnInfo to table in ActivityEntity so that it can store your data under a column and name it anything you like i just named it as activity

@ColumnInfo(name=&quot;activity&quot;)

无法创建我的AndroidViewModel实例。

无法创建我的AndroidViewModel实例。

huangapple
  • 本文由 发表于 2020年8月19日 09:21:08
  • 转载请务必保留本文链接：https://go.coder-hub.com/63478720.html
  • android
  • android-layout
  • android-mvvm
  • java
  • mvvm
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