如何修复 "lateinit property YYY has not been initialized"

Question

我有一个 class 可以建立蓝牙连接并从连接在汽车中的 OBD 蓝牙加密狗获取 PID。 但是当调用获取 RPM 的方法时，我有一个关于不初始化 属性.

的异常

class BluetoothOBDManager : OBDManager {
    lateinit var context: Context
    private lateinit var input: InputStream
    private lateinit var output: OutputStream
    private lateinit var rpmCommand: RPMCommand
    private lateinit var coolantTempCommand: EngineCoolantTemperatureCommand
    private lateinit var airIntakeTempCommand: AirIntakeTemperatureCommand
    private lateinit var mmSocket : BluetoothSocket

    fun connect(deviceString: String) {
        var adapter: BluetoothAdapter = getDefaultAdapter()
        val device = adapter.getRemoteDevice(deviceString)
        val uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")
        val mmSocket:BluetoothSocket=device.createRf....Record(uuid)

        mmSocket.let { socket ->
                socket.connect()
            }

        input = mmSocket.inputStream
        output = mmSocket.outputStream
        if (mmSocket.isConnected) {
            println("output.write =1")
            output.write(1)
        }
        rpmCommand = RPMCommand() //This is the INIT of the propert
    }

    override fun getCurrentRpm(): Int {
        rpmCommand.run(input, output) // This line throughs the EXCEPTION
        return rpmCommand.rpm
    }
}

我就是这样调用另一个方法的class

BluetoothOBDManager().connect(deviceString)
            var rpm  = BluetoothOBDManager().getCurrentRpm()
            rpmTextView.setText(rpm)

异常

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: gr.obd.logger, PID: 17486
    kotlin.UninitializedPropertyAccessException: lateinit property rpmCommand has not been initialized

我尝试在方法中初始化 属性 但没有成功

  override fun getCurrentRpm(): Int {
        rpmCommand = RPMCommand()
        rpmCommand.run(input, output) // This line throughs the EXCEPTION
        return rpmCommand.rpm
    }

Answer 1

BluetoothOBDManager().connect(deviceString)
        var rpm  = BluetoothOBDManager().getCurrentRpm()

您的代码创建一个 BluetoothOBDManager，连接它（初始化 rpmCommand），然后丢弃它，创建一个 new BluetoothOBDManager一切都未初始化并尝试调用 getCurrentRpm 。应该是

val obdManager = BluetoothOBDManager()
obdManager.connect(deviceString)
val rpm = obdManager.getCurrentRpm()

这并不能解释为什么你会得到

I have tried to INIT the property inside the method but no luck

但是真的不应该发生；我预计会出现其他问题。