android - lateinit 属性 llMain(RecyclerView) 尚未初始化

Question

我有带有 searchItem 和 tabHost 的 Activity 。 TabHost 有其他 Activity 。我在数据库中有一个搜索功能，它显示另一个 Activity 中的结果，该 Activity 位于 tabhost 中。但是当您尝试搜索时，它会出错:

kotlin.UninitializedPropertyAccessException: lateinit property llMain has not been initialized. 

我理解错误是当一个函数被调用时，它进入 viewTab 并试图调用 llMain。但我不知道如何解决这个问题。

class QuestionsActivity : AppCompatActivity(),WatchActivity.search{
    override fun searchQA(newText: String?) {
        if (newText != null) {
            val arraylis = db.search(newText)
            val search_date = Array(date.size) { "" }
            val search_id = IntArray(arraylis.size)
            val search_kategory = Array(arraylis.size) { "" }
            val search_summa = FloatArray(arraylis.size)
            ParseList().parse_search(arraylis,search_id,search_date,search_kategory,search_summa)
            Log.d("String", newText)
            ViewTab(search_id, search_date, search_kategory, search_summa)
        }
    }

    private lateinit var llMain: RecyclerView
    val adapter =  MyRecyclerViewAdapter()

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.questions_layout)
        llMain = findViewById(R.id.llMain)
//Other code
        }
 private fun ViewTab(id: IntArray, date: Array<String>, kategory: Array<String>,
                        summa: FloatArray) {
        val numberOfColumns = 1
        llMain.layoutManager = GridLayoutManager(this, numberOfColumns)
        adapter.MyRecyclerViewAdapter_(this, id, date, kategory,  summa)
        llMain.adapter = adapter
    }
}

class WatchActivity : AppCompatActivity(), SearchView.OnQueryTextListener {

    override fun onQueryTextSubmit(query: String?): Boolean {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

    override fun onQueryTextChange(newText: String?): Boolean {
        (qa as(search)).searchQA(newText)
        return false
    }

    interface search{
        fun searchQA(newText: String?)
    }

private val qa = QuestionsActivity()
    private lateinit var tabHost: TabHost
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.watch_layout)
        tabHost = findViewById(R.id.tabhost)
        val mLocalActivityManager = LocalActivityManager(this, false)
        mLocalActivityManager.dispatchCreate(savedInstanceState) // state will be bundle your activity state which you get in onCreate
        tabHost.setup(mLocalActivityManager)
        addTab("Расходы", "Расходы", qa::class.java)
tabHost.currentTab = 0

    }

    private fun addTab(spec: String, indic: String, classname: Class<*>) {
        val tabSpec = tabHost.newTabSpec(spec)
        tabSpec.setIndicator(indic)
        val intent = Intent(this, classname)
        tabSpec.setContent(intent)
        tabHost.addTab(tabSpec)
    }
}

XML代码:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                             xmlns:app="http://schemas.android.com/apk/res-auto"
                                             xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
                                             android:layout_height="match_parent">
    <TextView
            android:text="@string/numb"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/textView19"
            app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent"
            android:textSize="20sp" android:textColor="@android:color/background_dark" android:layout_marginTop="40dp"
            android:layout_marginLeft="4dp" android:layout_marginStart="4dp"/>
    <TextView
            android:text="@string/date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/textView20"
            android:textSize="20sp" app:layout_constraintStart_toEndOf="@+id/textView19"
            app:layout_constraintTop_toTopOf="parent" android:layout_marginLeft="28dp"
            android:layout_marginStart="28dp"
            android:clickable="true" android:textColor="@android:color/background_dark"
            android:layout_marginTop="40dp" android:focusable="true"/>
    <TextView
            android:text="@string/kate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/textView21"
            android:textSize="20sp" app:layout_constraintStart_toEndOf="@+id/textView19"
            app:layout_constraintTop_toTopOf="parent" android:layout_marginLeft="168dp"
            android:layout_marginStart="168dp" android:textColor="@android:color/background_dark"
            android:layout_marginTop="40dp"/>
    <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/textView22"
            android:textSize="20sp" app:layout_constraintStart_toEndOf="@+id/textView19"
            app:layout_constraintTop_toTopOf="parent" android:layout_marginLeft="320dp"
            android:layout_marginStart="320dp" android:textColor="@android:color/background_dark"
            android:layout_marginTop="40dp" android:text="@string/sum"/>
    <android.support.v7.widget.RecyclerView
            android:layout_width="407dp"
            android:id="@+id/llMain"
            android:layout_height="447dp"
            android:layout_x="-3dp"
            android:layout_y="-1dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" android:layout_marginBottom="203dp"
            android:layout_marginTop="8dp" app:layout_constraintTop_toBottomOf="@+id/textView20"/>
    <View
            android:id="@+id/view"
            android:visibility="gone"
            android:background="#CC000000"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    <com.getbase.floatingactionbutton.FloatingActionsMenu
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:id="@+id/multiplie_actions"
            android:layout_margin="16dp"
            android:layout_alignParentBottom="true"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true"
            app:fab_addButtonColorNormal="@color/colorPrimaryDark"
            app:fab_addButtonColorPressed="@color/colorAccent"
            app:fab_addButtonPlusIconColor="@android:color/background_light"
            app:fab_labelStyle="@style/menu_lables_style"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="92dp" android:layout_marginRight="92dp"
            android:layout_marginTop="10dp" app:layout_constraintTop_toBottomOf="@+id/searchView">
        <com.getbase.floatingactionbutton.FloatingActionButton
                android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                android:id="@+id/groupby"
                app:fab_title="Сгруппировать"
                app:fab_icon="@drawable/group"
                app:fab_colorNormal="#FFFFFF"
                app:fab_colorPressed="#BDBDBD"
                app:fab_size="normal"
                app:layout_constraintBottom_toTopOf="@+id/multiplie_actions"
                app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="12dp"
                android:layout_marginRight="12dp"/>
        <com.getbase.floatingactionbutton.FloatingActionButton
                android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                android:id="@+id/drop_table"
                app:fab_title="Очистить данные"
                app:fab_icon="@drawable/clear"
                app:fab_colorNormal="#FFFFFF"
                app:fab_colorPressed="#BDBDBD"
                app:fab_size="normal"
                app:layout_constraintBottom_toTopOf="@+id/multiplie_actions"
                app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="12dp"
                android:layout_marginRight="12dp"/>
    </com.getbase.floatingactionbutton.FloatingActionsMenu>
    <SearchView
            android:layout_width="402dp"
            android:layout_height="33dp"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginLeft="4dp" android:layout_marginStart="4dp" app:layout_constraintTop_toTopOf="parent"
            android:id="@+id/searchView">
    </SearchView>
</android.support.constraint.ConstraintLayout>

Answer 1

首先，您的代码在很多方面都存在严重错误，并且违反了常见的 Android 开发指南，包括命名、模式和良好做法。我建议您熟悉一些 Android 代码(例如由 Google 或 Square 编写的代码)或阅读一些有关 Android 开发的文献。

然而，由于您在使用此行创建的 Activity 实例上调用 (qa as(search)).searchQA(newText) 导致发生错误: private val qa = QuestionsActivity()。在那里，您覆盖了原始 QuestionsActivity.class 的 onCreate() 方法。 因此，您不再初始化 llMain 并且您收到错误...

简单地说，你没有这一行:

llMain = findViewById(R.id.llMain)

在 onCreate() 方法中，在 Activity 的重写方法中，您在此行中手动构建:private val qa = QuestionsActivity():

private val qa = QuestionsActivity()
    private lateinit var tabHost: TabHost
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.watch_layout)
        tabHost = findViewById(R.id.tabhost)
        val mLocalActivityManager = LocalActivityManager(this, false)
        mLocalActivityManager.dispatchCreate(savedInstanceState) // state will be bundle your activity state which you get in onCreate
        tabHost.setup(mLocalActivityManager)
        addTab("Расходы", "Расходы", qa::class.java)
tabHost.currentTab = 0

    }

onCreate() 方法中没有llMain 的初始化