Android Camera 2 API-textureView为null

Question

我一般对Kotlin和Android都很陌生。我试图做一个相机应用程序。当我启动该应用程序时，由于TextureView由于某种原因为null，它立即崩溃。我如何初始化它？很抱歉，如果它很琐碎，但我真的很难找到与此主题相关的最新教程和基于Kotlin的教程。更新：我没有在这里用方括号括起来，而是在代码中包含了方括号，不是由它引起的问题。

XML：

 <TextureView
        android:id="@+id/textureView"
        android:layout_width="447dp"
        android:layout_height="409dp"
        android:layout_marginTop="16dp"
        app:layout_constraintBottom_toTopOf="@+id/TakePicBtn"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" /> 

活动：

class CameraActivity : AppCompatActivity() {

    companion object {
        const val REQUEST_CAMERA_PERMISSION = 100
        private val TAG = this::class.qualifiedName
    }

    private val cameraManager by lazy { getSystemService(Context.CAMERA_SERVICE) as CameraManager }


    private fun <T> cameraCharacteristics(cameraId: String, key: CameraCharacteristics.Key<T>): T {
        val characteristics = cameraManager.getCameraCharacteristics(cameraId)
        return when (key) {
            CameraCharacteristics.LENS_FACING -> characteristics.get(key)
            CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP -> characteristics.get(key)
            else -> throw IllegalArgumentException("Key not recognised")
        }!!
    }

    private fun cameraId(lens: Int): String {
        var deviceId = listOf<String>()
        try {
            val cameraIdList = cameraManager.cameraIdList
            deviceId = cameraIdList.filter {
                lens == cameraCharacteristics(
                    it,
                    CameraCharacteristics.LENS_FACING
                )
            }
        } catch (e: CameraAccessException) {
            Log.e(TAG, e.toString())
        }
        return deviceId[0]
    }

    private fun connectCamera() {
        val deviceId = cameraId(CameraCharacteristics.LENS_FACING_BACK)
        Log.d(TAG, "devicesId: $deviceId")
    }

    override fun onResume() {
        super.onResume()

        if (textureView.isAvailable)
            openCamera()
        else{
            textureView.setBackgroundColor(Color.GRAY)
            textureView.surfaceTextureListener = surfaceListener
        }
    }

    private val surfaceListener = object: TextureView.SurfaceTextureListener {

        override fun onSurfaceTextureSizeChanged(surface: SurfaceTexture?, width: Int, height: Int) {
        }
        override fun onSurfaceTextureUpdated(surface: SurfaceTexture?) = Unit
        override fun onSurfaceTextureDestroyed(surface: SurfaceTexture?) = true
        override fun onSurfaceTextureAvailable(surface: SurfaceTexture?, width: Int, height: Int) {
            Log.d(TAG, "width: $width height: $height")
            openCamera()
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        EasyPermissions.onRequestPermissionsResult(requestCode,permissions,grantResults)
    }

    @AfterPermissionGranted(REQUEST_CAMERA_PERMISSION)
    private fun checkCameraPermission() {
        if (EasyPermissions.hasPermissions(this,CAMERA)){
            Log.d(TAG,"APP HAS CAMERA PERMISSION")
            connectCamera()
        } else {
            EasyPermissions.requestPermissions(this,"Camera app requires camera access",
                REQUEST_CAMERA_PERMISSION, CAMERA)
        }
    }

    private fun openCamera() {
        checkCameraPermission()
        // todo
    }

} 

输出：

  java.lang.RuntimeException: Unable to resume activity {.../...CameraActivity}: java.lang.IllegalStateException: textureView must not be null

Answer 1

跟进：仍然不确定我的代码出了什么问题，但是即使没有TextureView，它也仍然坏了，我必须弄乱了活动。重新进行该活动，它开始工作。在onCreate中缺少setContentView（R.layout.activity_camera），但即使这样也没有帮助。祝所有遇到类似问题的人都好运。