android - 如何使用 Android CameraX 自动对焦

Question

最近几个月，Android 发布了一个新的 API camerax。我试图了解如何让相机自动对焦。

https://groups.google.com/a/android.com/forum/#!searchin/camerax-developers/auto $20focus|sort:date/camerax-developers/IQ3KZd8iOIY/LIbrRIqEBgAJ

这是关于该主题的讨论，但几乎没有具体的文档。

https://github.com/android/camera-samples/tree/master/CameraXBasic/app/src/main/java/com/android/example/cameraxbasic

这也是基本的camerax应用程序，但我找不到任何处理自动对焦的文件。

任何有关文档的提示或要点都是有帮助的。此外，我对 android 还很陌生，所以很可能我遗漏了一些使上述链接更有用的东西。

标签： androidandroid-studiokotlinandroid-camerax

Answer 1

使用当前的 CameraX 1.0.0，您可以通过以下两种方式进行操作：

1. 每 X 秒自动对焦：

    previewView.afterMeasured {
        val autoFocusPoint = SurfaceOrientedMeteringPointFactory(1f, 1f)
                .createPoint(.5f, .5f)
        try {
            val autoFocusAction = FocusMeteringAction.Builder(
                autoFocusPoint,
                FocusMeteringAction.FLAG_AF
            ).apply {
                //start auto-focusing after 2 seconds
                setAutoCancelDuration(2, TimeUnit.SECONDS)
            }.build()
            camera.cameraControl.startFocusAndMetering(autoFocusAction)
        } catch (e: CameraInfoUnavailableException) {
            Log.d("ERROR", "cannot access camera", e)
        }
    }
   

2. 专注于点击：

    previewView.afterMeasured {
        previewView.setOnTouchListener { _, event ->
            return@setOnTouchListener when (event.action) {
                MotionEvent.ACTION_DOWN -> {
                    true
                }
                MotionEvent.ACTION_UP -> {
                    val factory: MeteringPointFactory = SurfaceOrientedMeteringPointFactory(
                        previewView.width.toFloat(), previewView.height.toFloat()
                    )
                    val autoFocusPoint = factory.createPoint(event.x, event.y)
                    try {
                        camera.cameraControl.startFocusAndMetering(
                            FocusMeteringAction.Builder(
                                autoFocusPoint,
                                FocusMeteringAction.FLAG_AF
                            ).apply {
                                //focus only when the user tap the preview
                                disableAutoCancel()
                            }.build()
                        )
                    } catch (e: CameraInfoUnavailableException) {
                        Log.d("ERROR", "cannot access camera", e)
                    }
                    true
                }
                else -> false // Unhandled event.
            }
        }
    }
   

afterMeasured扩展功能是一个简单的实用程序：（感谢 ch271828n改进它）

inline fun View.afterMeasured(crossinline block: () -> Unit) {
    if (measuredWidth > 0 && measuredHeight > 0) {
        block()
    } else {
        viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.GlobalLayoutListener {
            override fun onGlobalLayout() {
                if (measuredWidth > 0 && measuredHeight > 0) {
                    viewTreeObserver.removeOnGlobalLayoutListener(this)
                    block()
                } 
            }
        })
    }
}

Camera可以通过以下方式获得对象

val camera = cameraProvider.bindToLifecycle(
    this@Activity, cameraSelector, previewView //this is a PreviewView
)