通过 RunOnUIThread 更改 MainActivity 上的按钮颜色会崩溃

Question

我得到了

kotlin.UninitializedPropertyAccessException：lateinit 属性 BTNStatus05 尚未初始化

当我尝试设置 ButtonColor 时。 这个想法是根据通过 TCPsocket 的回复来更改按钮上的按钮颜色等。 在我的

我的主要活动简化：

class MainActivity() : AppCompatActivity(), Parcelable {
    constructor(parcel: Parcel) : this() {

    }
    private var fgm: SygicNaviFragment? = null
    private var uiInitialized = false
    private val TAG = "MainActivity"
    private lateinit var socketHandler: SocketHandler
    private lateinit var handlerThread: HandlerThread
    lateinit var BTNStatus05 : Button


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        if (PermissionsUtils.requestStartupPermissions(this) == PackageManager.PERMISSION_GRANTED) {
            checkSygicResources()
            Log.i(TAG, "onCreate: Sygic Resources checked")
        }
        //this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN)

        window.decorView.apply {
           systemUiVisibility = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or View.SYSTEM_UI_FLAG_FULLSCREEN
        }
        setContentView(R.layout.activity_main)

        handlerThread = HandlerThread("").apply {
            start()
            socketHandler = SocketHandler(looper)


            socketHandler?.obtainMessage()?.also { msg ->
                msg.what = 0
                msg.obj = "INIT"
                msg.arg1 = 0
                socketHandler?.sendMessage(msg)}

        }
       
        // set on-click listener
        BTNStatus05= findViewById(R.id.statusbutton05) as Button
        Log.d(TAG, "BTN05" + BTNStatus05)
            //BTNStatus05.setBackgroundColor(Color.YELLOW)
            //BTNStatus05.setEnabled(false)
        BTNStatus05.setOnClickListener {
            socketHandler?.obtainMessage()?.also { msg ->
                msg.what = 1
                msg.obj = "btnpress"
                msg.arg1 = 5
                socketHandler?.sendMessage(msg)
            }
            Toast.makeText(this@MainActivity, "Status05 Clicked.", Toast.LENGTH_SHORT).show()
        }
            
    fun Test() {
           Log.d(TAG, "DATA on Mainthread? " + Thread.currentThread().name)
           Log.d(TAG, "Stop: We Got a button:")
           BTNStatus05.setBackgroundColor(Color.YELLOW)
           BTNStatus05.setEnabled(false)
    }

    override fun onCreateDialog(id: Int): Dialog {
        return fgm?.onCreateDialog(id) ?: return super.onCreateDialog(id)
    }

    override fun onPrepareDialog(id: Int, dialog: Dialog) {
        super.onPrepareDialog(id, dialog)
        fgm?.onPrepareDialog(id, dialog)
    }

    override fun onNewIntent(intent: Intent?) {
        super.onNewIntent(intent)
        fgm!!.onNewIntent(intent)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        fgm?.onActivityResult(requestCode, resultCode, data)
    }

    override fun onKeyDown(keyCode: Int, event: KeyEvent?): Boolean {
        return fgm?.onKeyDown(keyCode, event) ?: return super.onKeyDown(keyCode, event)
    }

    override fun onKeyUp(keyCode: Int, event: KeyEvent?): Boolean {
        return fgm?.onKeyUp(keyCode, event) ?: return super.onKeyUp(keyCode, event)
    }



    override fun writeToParcel(parcel: Parcel, flags: Int) {

    }


       override fun describeContents(): Int {
        return 0
    }

    companion object CREATOR : Parcelable.Creator<MainActivity> {
        override fun createFromParcel(parcel: Parcel): MainActivity {
            return MainActivity(parcel)
        }

        override fun newArray(size: Int): Array<MainActivity?> {
            return arrayOfNulls(size)
        }
    }


   inner class MainHandler(mainlooper: Looper) : Handler(mainlooper) {
        private val TAG = "MainActivity"
        val mainA = MainActivity()
       val mapper = jacksonObjectMapper()
        override fun handleMessage(msg: Message) {
            Log.d(TAG, "Handle")
            super.handleMessage(msg)
            val jsonstr = msg?.obj as String
            val jsontree = mapper.readTree(jsonstr)
            val type = jsontree.get("type").asText()
            Log.d(TAG, "Mainhandler: jsonstr - " + jsonstr)
            Log.d(TAG, "MainHandler:Json type -  " + type )
            when(type) {
                           "button" -> {
                    Log.d(TAG, "We got button update: " + type)

                        MainActivity().runOnUiThread(Runnable {
                        BTNStatus05.setBackgroundColor(Color.YELLOW) })
                        //BTNStatus05.setBackgroundColor(Color.YELLOW)

                }
                else -> Log.d(TAG, "unknown what " + type)
            }
                   }
    }
}

我尝试过：

when(type) {
                           "button" -> {
                    Log.d(TAG, "We got button update: " + type)

                        MainActivity().runOnUiThread(Runnable {
                        BTNStatus05.setBackgroundColor(Color.YELLOW) })
                        //BTNStatus05.setBackgroundColor(Color.YELLOW)

                }
                else -> Log.d(TAG, "unknown what " + type)

而且也只是打电话给

test()

...有什么想法吗？

Answer 1

kotlin.UninitializedPropertyAccessException: lateinit property BTNStatus05 has not been initialized

此异常要求您的代码正在访问声明为

lateinit

并且尚未初始化的属性。因此，当您将

BTNStatus05

声明为

lateinit

时，您必须在代码上的任何其他行访问它之前对其进行初始化。在您的情况下，当

MainHandler

调用

BTNStatus05.setBackgroundColor(Color.YELLOW)

时，

BTNStatus05

未初始化。

要解决此问题，只需将按钮

BTNStatus05= findViewById(R.id.statusbutton05) as Button

的这一行初始化移动到

onCreate

方法的第一行内，如下所示。

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    BTNStatus05= findViewById(R.id.statusbutton05)
    // Other code
}

这将在访问之前初始化您的按钮，并且不会抛出相同的异常。