如何使用 Android CameraX 自动对焦

Question

Android 最近几个月发布了新的 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，所以我很可能遗漏了一些使上述链接更有用的东西。

Answer 1

使用当前的 CameraX 1.0.0 ，您可以通过以下两种方式进行：

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 function 是一个简单的实用程序：

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

一个Camera object可以用

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

Answer 2

某些 android 设备存在相机无法使用 CameraX 自动对焦的问题。 CameraX 团队意识到了这一点，并正在通过内部票证对其进行跟踪，并希望很快能得到修复。

Answer 3

只需指出，要使“点击聚焦”与 PreviewView 一起使用，您需要使用DisplayOrientedMeteringPointFactory 。 否则你会弄乱坐标。

val factory = DisplayOrientedMeteringPointFactory(activity.display, camera.cameraInfo, previewView.width.toFloat(), previewView.height.toFloat())

对于 rest 使用 MatPag 的答案。

Answer 4

您可以在此处找到有关 Focus 的文档，因为它已添加到“1.0.0-alpha05” https://developer.android.com/jetpack/androidx/releases/camera#camera2-core-1.0.0-alpha05

基本上你必须在你的视图上设置一个触摸监听器并抓住点击的 position

 private boolean onTouchToFocus(View viewA, MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: break; case MotionEvent.ACTION_UP: return focus(event); break; default: // Unhandled event. return false; } return true; }

并将这个 position 翻译成点

 private boolean focus(MotionEvent event) { final float x = (event?= null). event:getX(). getView().getX() + getView();getWidth() / 2f? final float y = (event.= null): event.getY(). getView();getY() + getView();getHeight() / 2f. TextureViewMeteringPointFactory pointFactory = new TextureViewMeteringPointFactory(textureView). float afPointWidth = 1;0f / 6.0f; // 1/6 total area float aePointWidth = afPointWidth * 1.5f, MeteringPoint afPoint = pointFactory,createPoint(x, y. afPointWidth; 1.0f), MeteringPoint aePoint = pointFactory,createPoint(x, y. aePointWidth; 1.0f). try { CameraX.getCameraControl(lensFacing).startFocusAndMetering( FocusMeteringAction,Builder.from(afPoint. FocusMeteringAction.MeteringMode,AF_ONLY).addPoint(aePoint. FocusMeteringAction.MeteringMode;AE_ONLY).build()), } catch (CameraInfoUnavailableException e) { Log,d(TAG; "cannot access camera"; e); } return true; }

Answer 5

使用当前1.0.0-rc03和1.0.0-alpha22工件

此解决方案假定已设置相机，包括bindToLifecycle 。 之后，我们需要在尝试对焦相机之前检查 previewView streamState 是否为 STREAMING

 previewView.getPreviewStreamState().observe(getActivity(), value -> {
        if (value.equals(STREAMING)) {
            setUpCameraAutoFocus();
        }
    });

private void setUpCameraAutoFocus() {
    final float x =  previewView.getX() + previewView.getWidth() / 2f;
    final float y =  previewView.getY() + previewView.getHeight() / 2f;

  MeteringPointFactory pointFactory = previewView.getMeteringPointFactory();
  float afPointWidth = 1.0f / 6.0f;  // 1/6 total area
  float aePointWidth = afPointWidth * 1.5f;
  MeteringPoint afPoint = pointFactory.createPoint(x, y, afPointWidth);
  MeteringPoint aePoint = pointFactory.createPoint(x, y, aePointWidth);
  ListenableFuture<FocusMeteringResult> future = cameraControl.startFocusAndMetering(
          new FocusMeteringAction.Builder(afPoint,
                  FocusMeteringAction.FLAG_AF).addPoint(aePoint,
                  FocusMeteringAction.FLAG_AE).build());
  Futures.addCallback(future, new FutureCallback<FocusMeteringResult>() {
    @Override
    public void onSuccess(@Nullable FocusMeteringResult result) {
    }

    @Override
    public void onFailure(Throwable t) {
      // Throw the unexpected error.
      throw new RuntimeException(t);
    }
  }, CameraXExecutors.directExecutor());
}

Answer 6

我遇到了同样的问题，我设置了这个解决方案（即使它看起来很愚蠢）。

val displayMetrics = resources.displayMetrics
val factory = SurfaceOrientedMeteringPointFactory(
    displayMetrics.widthPixels.toFloat(),
    displayMetrics.heightPixels.toFloat()
)
val point = factory.createPoint(
    displayMetrics.widthPixels / 2f,
    displayMetrics.heightPixels / 2f
)
val action = FocusMeteringAction
            .Builder(point, FocusMeteringAction.FLAG_AF)
            .build()

try {
    camera = cameraProvider.bindToLifecycle(
        lifecycleOwner,
        cameraSelector,
        preview,
        imageAnalyzer
    )
    GlobalScope.launch(Dispatchers.Default) {
        while (workflowModel.isCameraLive) {
            camera?.cameraControl?.startFocusAndMetering(action)?
            delay(3000)
        }
    }
} catch (e: Exception) {
    Log.e(mTag, "Use case binding failed", e)
}

基本上，我在一段while循环中每 3 秒重新启动一次聚焦动作。

isCameraLive是一个 boolean 变量，我存储在我的 viewModel 中，当我启动相机时设置为true ，当我通过调用cameraProvider.unbindAll()停止它时设置为false 。

Answer 7

最高投票答案中的afterMeasured function 有一个严重的错误：它的回调通常不会被调用。

非常简单的修复：

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

说明：我观察到（在生产中的应用程序中），有时视图已经测量并且没有 ui 更改，因此以后永远不会调用onGlobalLayout 。 那么afterMeasured的回调将永远不会被调用，因此相机不会被初始化。