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android - 尽管初始化，对象在 Kotlin 中仍处于未初始化状态

问题描述

我正在我的方法中初始化我的RecyclerView对象，但不知何故它没有通过。我正在使用该函数来初始化我的对象并附加其必要的属性：MainActivity.ktonCrete()applyRecyclerView

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

        ...

        adapter = EntryAdapter()
        layoutManager = LinearLayoutManager(this)

        recyclerView.apply{
            findViewById<RecyclerView>(R.id.userpass_recyclerview)
            layoutManager = layoutManager
            adapter = adapter
        }

        ...
    }

这是我得到的错误：

Process: com.example.cryptpass_kt, PID: 29095
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.cryptpass_kt/com.example.cryptpass_kt.MainActivity}: kotlin.UninitializedPropertyAccessException: lateinit property recyclerView has not been initialized
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2853)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2928)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1609)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6703)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:769)
     Caused by: kotlin.UninitializedPropertyAccessException: lateinit property recyclerView has not been initialized
        at com.example.cryptpass_kt.MainActivity.onCreate(MainActivity.kt:46)
        at android.app.Activity.performCreate(Activity.java:6980)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2806

标签： androidkotlin

解决方案

调用apply（与任何其他方法一样）方法需要已经初始化的对象。但是您正试图在apply的 lambda 中对其进行初始化。

所以你需要先打电话findViewById：

recyclerView = findViewById<RecyclerView>(R.id.userpass_recyclerview)
recyclerView.apply {...}

或者，要获得更少的代码：

recyclerView = findViewById<RecyclerView>(R.id.userpass_recyclerview).apply {
    ...
}

并且不要忘记，您应该findViewById只在setContentView.

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