我正在学习android MVVM模式android开发。我想创建一个recycclerview Activity 以显示来自服务器的数据。但这不接受我的viewmodel类。波纹管是我的logcat错误。
LOGCAT
2020-04-12 21:03:18.026 2008-2008/com.shovon.mvvm E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.shovon.mvvm, PID: 2008
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.shovon.mvvm/com.shovon.mvvm.activity.RecyclerActivity}: java.lang.RuntimeException: Cannot create an instance of class com.shovon.mvvm.viewmodel.RecyclerActivityViewModel
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.RuntimeException: Cannot create an instance of class com.shovon.mvvm.viewmodel.RecyclerActivityViewModel
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:221)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.shovon.mvvm.activity.RecyclerActivity.onCreate(RecyclerActivity.kt:23)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
**Caused by: java.lang.InstantiationException: java.lang.Class<com.shovon.mvvm.viewmodel.RecyclerActivityViewModel> has no zero argument constructor**
at java.lang.Class.newInstance(Native Method)
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:219)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.shovon.mvvm.activity.RecyclerActivity.onCreate(RecyclerActivity.kt:23)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
View 模型
这是我的viewmodel类。我正在从此 View 模型向 Activity 传递一些数据。但是问题是 Activity 不接受该 View 模型。也许viewmodel有任何问题。
class RecyclerActivityViewModel(application: Application) : AndroidViewModel(application) {
val repository = RecyclerActivityRepository(application)
fun userData(): LiveData<ArrayList<UserResponse>>{
return repository.getUserData()
}
}
仓库
class RecyclerActivityRepository(application: Application) {
var liveData = MutableLiveData<ArrayList<UserResponse>>()
private val userList = ArrayList<UserResponse>()
private var adapter: UserAdapter? = null
fun getUserData(): MutableLiveData<ArrayList<UserResponse>>{
if (liveData == null){
liveData = MutableLiveData<ArrayList<UserResponse>>()
}
RetrofitClient.instance.getUsers()
.enqueue(object : Callback<List<UserResponse>> {
override fun onFailure(call: Call<List<UserResponse>>, t: Throwable) {
Log.v("Retrofit", t.message.toString())
}
override fun onResponse(
call: Call<List<UserResponse>>,
response: Response<List<UserResponse>>
) {
Log.v("Retrofit", "Success")
Log.v("response_code", response.code().toString())
try {
userList.addAll(response.body()!!)
adapter?.notifyDataSetChanged()
}catch (e: Exception){
Log.v("error", e.message.toString())}
}
})
return liveData
}
}
Activity
这是我的逻辑代码
class RecyclerActivity : AppCompatActivity() {
private lateinit var viewModel: RecyclerActivityViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_recycler)
viewModel = ViewModelProvider(this).get(RecyclerActivityViewModel::class.java)
}
}
最佳答案
这可能会有所帮助
viewModel= ViewModelProvider(this, ViewModelProvider.AndroidViewModelFactory.getInstance(this.getApplication())).get(RecyclerActivityViewModel::class.java)
关于android - 无法在Android MVVM中创建ViewModel类的实例，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/61173893/