如何在CameraX上切换到前置摄像头？ [英] How to switch to front camera on CameraX?

问题描述

我已按照步骤此处获取CameraX设置，现在我正在尝试使前置摄像头按钮正常工作。

I've followed the steps here to get CameraX setup, and now I am trying to get a front facing camera button working.

这是我的设置代码：

private lateinit var preview: Preview

private fun startCamera() {

    // Create configuration object for the viewfinder use case
    val previewConfig = PreviewConfig.Builder().apply {
        setLensFacing(CameraX.LensFacing.BACK)
    }.build()

    // Build the viewfinder use case
    preview = Preview(previewConfig)

    // Every time the viewfinder is updated, recompute layout
    preview.setOnPreviewOutputUpdateListener {

        // To update the SurfaceTexture, we have to remove it and re-add it
        val parent = viewFinder.parent as ViewGroup
        parent.removeView(viewFinder)
        parent.addView(viewFinder, 0)

        viewFinder.surfaceTexture = it.surfaceTexture
        updateTransform()
    }

    // Bind use cases to lifecycle
    CameraX.bindToLifecycle(this, preview)
}

当用户单击时我使用切换按钮将预览重新配置为使用前置摄像头，然后重新初始化预览。

When a user clicks the "switch" button I re-configure the preview to use the front camera, then reinitialize the Preview.

private fun initSwitchButton(view: View) {
    switchButton = view.findViewById(R.id.switch_button)
    switchButton.setOnClickListener {
        val previewConfig = PreviewConfig.Builder().apply { setLensFacing(CameraX.LensFacing.FRONT) }.build()
        preview = Preview(previewConfig)
    }
}

但是，这不会切换到前置摄像头。我缺少什么？

However, this doesn't switch to the front camera. What am I missing?

推荐答案

它看起来像推荐的方法以实现此目的将 LensFacing 位置存储为实例变量，然后调用 bindToLifecycle（）切换相机。

It looks like the recommended way to achieve this is to store the LensFacing position as an instance variable and then call bindToLifecycle() to switch the camera.

以下是对我有用的代码段：

Here is a code snippet that worked for me:

private var lensFacing = CameraX.LensFacing.BACK
private var imageCapture: ImageCapture? = null

@SuppressLint("RestrictedApi")
private fun startCamera() {
    bindCameraUseCases()

    // Listener for button used to switch cameras
    switchButton = view.findViewById(R.id.switch_button)
    switchButton.setOnClickListener {
        lensFacing = if (CameraX.LensFacing.FRONT == lensFacing) {
            CameraX.LensFacing.BACK
        } else {
            CameraX.LensFacing.FRONT
        }
        try {
            // Only bind use cases if we can query a camera with this orientation
            CameraX.getCameraWithLensFacing(lensFacing)
            bindCameraUseCases()
        } catch (exc: Exception) {
            // Do nothing
        }
    }
}

private fun bindCameraUseCases() {
    // Make sure that there are no other use cases bound to CameraX
    CameraX.unbindAll()

    val previewConfig = PreviewConfig.Builder().apply {
        setLensFacing(lensFacing)
    }.build()
    val preview = Preview(previewConfig)

    val imageCaptureConfig = ImageCaptureConfig.Builder().apply {
        setLensFacing(lensFacing)
    }.build()
    imageCapture = ImageCapture(imageCaptureConfig)

    // Apply declared configs to CameraX using the same lifecycle owner
    CameraX.bindToLifecycle(this, preview, imageCapture)
}

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