java.lang.IllegalArgumentException：指定為非空的參數是 null：- android，應用程序啟動但立即崩潰

Question

嘿伙計們，我在啟動我的應用程序時遇到問題，我不知道是什么問題，當我啟動它時它會立即崩潰，從日志中我想這是關於數據綁定的問題，但我真的不知道出了什么問題對現在：C

2020-04-10 22:22:22.716 32624-32624/? I/rss.ing_projec: Late-enabling -Xcheck:jni
2020-04-10 22:22:22.746 32624-32624/? E/rss.ing_projec: Unknown bits set in runtime_flags: 0x8000
2020-04-10 22:22:23.053 32624-32624/com.lswarss.ing_project I/Perf: Connecting to perf service.
2020-04-10 22:22:23.070 32624-32624/com.lswarss.ing_project V/Font: Change font:1
2020-04-10 22:22:23.071 32624-32624/com.lswarss.ing_project V/Font: Default family:android.graphics.Typeface@177a2b82
2020-04-10 22:22:23.077 32624-32676/com.lswarss.ing_project E/Perf: Fail to get file list com.lswarss.ing_project
2020-04-10 22:22:23.077 32624-32676/com.lswarss.ing_project E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2020-04-10 22:22:23.077 32624-32676/com.lswarss.ing_project E/Perf: Fail to get file list com.lswarss.ing_project
2020-04-10 22:22:23.078 32624-32676/com.lswarss.ing_project E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2020-04-10 22:22:23.156 32624-32624/com.lswarss.ing_project W/rss.ing_projec: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
2020-04-10 22:22:23.157 32624-32624/com.lswarss.ing_project W/rss.ing_projec: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
2020-04-10 22:22:23.213 32624-32624/com.lswarss.ing_project V/FlingOptimizerScroller: FlingOptimizerOverScroller Init
2020-04-10 22:22:23.251 32624-32624/com.lswarss.ing_project D/AndroidRuntime: Shutting down VM
2020-04-10 22:22:23.253 32624-32624/com.lswarss.ing_project E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.lswarss.ing_project, PID: 32624
    java.lang.RuntimeException: Failed to call observer method
        at androidx.lifecycle.ClassesInfoCache$MethodReference.invokeCallback(ClassesInfoCache.java:226)
        at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeMethodsForEvent(ClassesInfoCache.java:194)
        at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeCallbacks(ClassesInfoCache.java:185)
        at androidx.lifecycle.ReflectiveGenericLifecycleObserver.onStateChanged(ReflectiveGenericLifecycleObserver.java:37)
        at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361)
        at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300)
        at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339)
        at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145)
        at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131)
        at androidx.fragment.app.Fragment.performStart(Fragment.java:2735)
        at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:365)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1194)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManager.dispatchStart(FragmentManager.java:2583)
        at androidx.fragment.app.Fragment.performStart(Fragment.java:2739)
        at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:365)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1194)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManager.dispatchStart(FragmentManager.java:2583)
        at androidx.fragment.app.FragmentController.dispatchStart(FragmentController.java:258)
        at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:550)
        at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1514)
        at android.app.Activity.performStart(Activity.java:7838)
        at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3398)
        at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
        at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2109)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7682)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
     Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter data
        at com.lswarss.ing_project.adapters.BindingAdaptersKt.bindRecyclerView(Unknown Source:7)
        at com.lswarss.ing_project.databinding.PostsFragmentBindingImpl.executeBindings(PostsFragmentBindingImpl.java:125)
2020-04-10 22:22:23.253 32624-32624/com.lswarss.ing_project E/AndroidRuntime:     at androidx.databinding.ViewDataBinding.executeBindingsInternal(ViewDataBinding.java:473)
        at androidx.databinding.ViewDataBinding.executePendingBindings(ViewDataBinding.java:445)
        at androidx.databinding.ViewDataBinding$OnStartListener.onStart(ViewDataBinding.java:1687)
        at java.lang.reflect.Method.invoke(Native Method)
        at androidx.lifecycle.ClassesInfoCache$MethodReference.invokeCallback(ClassesInfoCache.java:216)
            ... 41 more

那是 android 工作室給出的日志 這個 class 有一些問題，但它有什么問題：

package com.lswarss.ing_project.adapters

import android.view.View
import android.widget.ImageView
import androidx.databinding.BindingAdapter
import androidx.recyclerview.widget.RecyclerView
import com.lswarss.ing_project.R
import com.lswarss.ing_project.domain.PostItem
import com.lswarss.ing_project.fragments.PostsApiStatus

@BindingAdapter("listData")
fun bindRecyclerView(recyclerView: RecyclerView, data: List<PostItem>?){
    val adapter  = recyclerView.adapter as PostsAdapter
    adapter.submitList(data)
}


@BindingAdapter("postApiStatus")
fun bindStatus(statusImageView: ImageView, status: PostsApiStatus?) {
    when (status) {
        PostsApiStatus.LOADING -> {
            statusImageView.visibility = View.VISIBLE
            statusImageView.setImageResource(R.drawable.loading_animation)
        }
        PostsApiStatus.ERROR -> {
            statusImageView.visibility = View.VISIBLE
            statusImageView.setImageResource(R.drawable.ic_connection_error)
        }
        PostsApiStatus.DONE -> {
            statusImageView.visibility = View.GONE
        }
    }
}

我正在嘗試使用 udacity course Mars Real Estate App中制作的應用程序來執行此應用程序

這是 github 上我的應用程序的鏈接： https://github.com/LSWarss/ing_project我遇到問題的代碼在分支 new_architecture

對不起，如果這是一個愚蠢的問題，但我是 android 和 koltlin 的新手，甚至在堆棧上發帖：)

Answer 1

   Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter data
   at com.lswarss.ing_project.adapters.BindingAdaptersKt.bindRecyclerView(Unknown Source:7

發生這種情況是因為只要我從 github 看到，在您的PostsFragment中，您沒有將適配器設置為回收器視圖，因此當綁定適配器嘗試訪問它時，它是null 。

另外，我在您的主分支中注意到了這一點：

viewModel.posts.observe(viewLifecycleOwner, Observer {
    posts -> recycler_view_posts.also{
    it.layoutManager = LinearLayoutManager(requireContext())
    it.setHasFixedSize(true)
    it.adapter = PostsAdapter(posts)
}

每次觀察到某些東西時，您不必初始化您的回收站視圖。

在片段的onViewCreated()方法中，您可以設置適配器和 layoutManager（如果您在 PostsFragment 中添加它，這也將解決您的錯誤）：

private fun initRecyclerView(){
    recycler_view_posts.run{
        adapter = PostsAdapter(posts)
        layoutManager = LinearLayoutManager(requireContext())
        setHasFixedSize(true)
    }
}

然后觀察你只需要使用 new_architecture 分支（ adapter.submitList(list) ）的方法或通過在適配器中設置新列表並調用adapter.notifyDataSetChange()來刷新內容。

Answer 2

將bindRecyclerView更改為：

@BindingAdapter("listData")
fun bindRecyclerView(recyclerView: RecyclerView, data: List<PostItem>?){
    val adapter  = recyclerView.adapter as PostsAdapter? // changed to nullable type
    adapter?.submitList(data)// nullablity checked
}