我正在尝试使用本教程实现 CameraX:https://codelabs.developers.google.com/codelabs/camerax-getting-started/#5我的应用程序有一个 Activity、导航主机和两个片段。我还在我的片段上使用数据绑定。当我尝试获取显示旋转时,出现错误。
这是我的布局文件:
<?xml version="1.0" encoding="utf-8"?>
<layout 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">
<data>
<variable
name="viewModel"
type="com.ayonix.faceticket.camerapreview.CameraPreviewViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".camerapreview.CameraPreviewFragment">
<TextureView
android:id="@+id/camera_preview"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintDimensionRatio="9:16"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
这是我的片段代码:
class CameraPreviewFragment : Fragment() {
private lateinit var binding: CameraPreviewFragmentBinding
private lateinit var viewModel: CameraPreviewViewModel
private val previewConfig = PreviewConfig.Builder().build()
private val preview = Preview(previewConfig)
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = CameraPreviewFragmentBinding.inflate(inflater, container, false)
binding.lifecycleOwner = this
val viewModelFactory = CameraPreviewViewModelFactory((activity as MainActivity).faceIDUtils)
viewModel = ViewModelProviders.of(this, viewModelFactory).get(CameraPreviewViewModel::class.java)
binding.viewModel = viewModel
startCamera()
return binding.root
}
private fun startCamera() {
preview.setOnPreviewOutputUpdateListener {
val parent = binding.cameraPreview.parent as ViewGroup
parent.removeView(binding.cameraPreview)
parent.addView(binding.cameraPreview, 0)
binding.cameraPreview.surfaceTexture = it.surfaceTexture
updateTransform()
}
CameraX.bindToLifecycle(this, preview, viewModel.analyzerUseCase)
}
private fun updateTransform() {
val matrix = Matrix()
val centerX = binding.cameraPreview.width / 2f
val centerY = binding.cameraPreview.height / 2f
val rotationDegrees = when(binding.cameraPreview.display.rotation) {
Surface.ROTATION_0 -> 0
Surface.ROTATION_90 -> 90
Surface.ROTATION_180 -> 180
Surface.ROTATION_270 -> 270
else -> return
}
matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)
binding.cameraPreview.setTransform(matrix)
}
}
我尝试过像这样旋转
binding.root.display.rotation
。但它也给出了同样的错误。
错误如下:
java.lang.IllegalStateException: binding.cameraPreview.display must not be null
3个月后我找到了原因。 startCamera() 必须在 onViewCreated 中调用。除了膨胀布局之外,您不应该在 onCreateView() 中执行任何操作。固定代码是这样的:
class CameraPreviewFragment : Fragment() {
private lateinit var binding: CameraPreviewFragmentBinding
private lateinit var viewModel: CameraPreviewViewModel
private val previewConfig = PreviewConfig.Builder().build()
private val preview = Preview(previewConfig)
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = CameraPreviewFragmentBinding.inflate(inflater, container, false)
binding.lifecycleOwner = this
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val viewModelFactory = CameraPreviewViewModelFactory((activity as MainActivity).faceIDUtils)
viewModel =
ViewModelProviders.of(this, viewModelFactory).get(CameraPreviewViewModel::class.java)
binding.viewModel = viewModel
startCamera()
}
private fun startCamera() {
preview.setOnPreviewOutputUpdateListener {
val parent = binding.cameraPreview.parent as ViewGroup
parent.removeView(binding.cameraPreview)
parent.addView(binding.cameraPreview, 0)
binding.cameraPreview.surfaceTexture = it.surfaceTexture
updateTransform()
}
CameraX.bindToLifecycle(this, preview, viewModel.analyzerUseCase)
}
private fun updateTransform() {
val matrix = Matrix()
val centerX = binding.cameraPreview.width / 2f
val centerY = binding.cameraPreview.height / 2f
val rotationDegrees = when (binding.cameraPreview.display.rotation) {
Surface.ROTATION_0 -> 0
Surface.ROTATION_90 -> 90
Surface.ROTATION_180 -> 180
Surface.ROTATION_270 -> 270
else -> return
}
matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)
binding.cameraPreview.setTransform(matrix)
}
}
另一种选择,在我的例子中,我从 Activity 启动它,是使用“View.post { startCamera() }”,因为 updateTransform 在视图准备好之前被访问。
在 onViewCreated(fragment 中) 或 onAttachedToWindow(activity 中) 中调用 getDisplay, 在某些情况下显示可能为空