關於在 Android Studio 中實現 CameraX 預覽的問題

Question

我試圖為 CameraX 實現預覽，但我的代碼中有兩個錯誤，我無法解決：

1. CameraSelector 在 androidx.camera.core.CameraSelector 中不公開。 無法從 package 外部訪問。

2. 無法解析符號“previewView”

編輯：我解決了問題，但我仍然沒有得到預覽。 我之前沒有提到，但我在 Android Manifest 中插入了權限。

這是我的代碼：

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        PreviewView previewView = (PreviewView) findViewById(R.id.previewView);

        cameraProviderFuture = ProcessCameraProvider.getInstance(this);

        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                Preview preview = new Preview.Builder().build();
                CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build(); 
                preview.setSurfaceProvider(previewView.createSurfaceProvider());     
                cameraProvider.unbindAll();
                cameraProvider.bindToLifecycle((LifecycleOwner)this, cameraSelector, preview);
            } catch (ExecutionException | InterruptedException e) {
                e.printStackTrace();
            }
        }, ContextCompat.getMainExecutor(this));

    }

}

Build.gradle（模塊：應用程序），內部依賴項部分

def camerax_version = "1.0.0-beta07"
implementation "androidx.camera:camera-core:$camerax_version"
implementation "androidx.camera:camera-camera2:$camerax_version"
implementation "androidx.camera:camera-lifecycle:$camerax_version"
implementation "androidx.camera:camera-view:1.0.0-alpha14"

activity_main.xml

<RelativeLayout
    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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.camera.view.PreviewView
        android:id="@+id/previewView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

我知道 createSurfaceProvider() 自 Camera-View Version 1.0.0-alpha16 以來已重命名為 getSurfaceProvider()，但是當我嘗試調用最后一個方法時 Android Studio 沒有解決它。

這是日志（錯誤）

2020-11-22 20:59:01.944 10830-10830/? E/Zygote: isWhitelistProcess - Process is Whitelisted
2020-11-22 20:59:01.945 10830-10830/? E/Zygote: accessInfo : 1
2020-11-22 20:59:03.214 10830-10885/com.android.unipi.camerademo E/Camera_APM :: [APM]APM's Thread is started
2020-11-22 20:59:03.216 10830-10885/com.android.unipi.camerademo E/Camera_APM :: [APM] This app is forground app
2020-11-22 20:59:03.223 10830-10872/com.android.unipi.camerademo E/SequentialExecutor: Exception while executing runnable androidx.camera.camera2.internal.-$$Lambda$Camera2CameraImpl$_NFNV64YCFFY0Tn3VRiyE3Ss3S0@5d0b8a
    java.lang.SecurityException: validateClientPermissionsLocked:1145: Caller "com.android.unipi.camerademo" (PID 10188, UID 10830) cannot open camera "0" without camera permission
        at android.hardware.camera2.CameraManager.throwAsPublicException(CameraManager.java:855)
        at android.hardware.camera2.CameraManager.openCameraDeviceUserAsync(CameraManager.java:499)
        at android.hardware.camera2.CameraManager.openCameraForUid(CameraManager.java:670)
        at android.hardware.camera2.CameraManager.openCamera(CameraManager.java:638)
        at androidx.camera.camera2.internal.compat.CameraManagerCompatApi28Impl.openCamera(CameraManagerCompatApi28Impl.java:70)
        at androidx.camera.camera2.internal.compat.CameraManagerCompat.openCamera(CameraManagerCompat.java:185)
        at androidx.camera.camera2.internal.Camera2CameraImpl.openCameraDevice(Camera2CameraImpl.java:871)
        at androidx.camera.camera2.internal.Camera2CameraImpl.openInternal(Camera2CameraImpl.java:236)
        at androidx.camera.camera2.internal.Camera2CameraImpl.tryAttachUseCases(Camera2CameraImpl.java:691)
        at androidx.camera.camera2.internal.Camera2CameraImpl.lambda$attachUseCases$10$Camera2CameraImpl(Camera2CameraImpl.java:649)
        at androidx.camera.camera2.internal.-$$Lambda$Camera2CameraImpl$_NFNV64YCFFY0Tn3VRiyE3Ss3S0.run(Unknown Source:4)
        at androidx.camera.core.impl.utils.executor.SequentialExecutor$QueueWorker.workOnQueue(SequentialExecutor.java:230)
        at androidx.camera.core.impl.utils.executor.SequentialExecutor$QueueWorker.run(SequentialExecutor.java:172)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: android.os.ServiceSpecificException: validateClientPermissionsLocked:1145: Caller "com.android.unipi.camerademo" (PID 10188, UID 10830) cannot open camera "0" without camera permission (code 1)
        at android.os.Parcel.createException(Parcel.java:1980)
        at android.os.Parcel.readException(Parcel.java:1934)
        at android.os.Parcel.readException(Parcel.java:1884)
        at android.hardware.ICameraService$Stub$Proxy.connectDevice(ICameraService.java:359)
        at android.hardware.camera2.CameraManager.openCameraDeviceUserAsync(CameraManager.java:463)
        at android.hardware.camera2.CameraManager.openCameraForUid(CameraManager.java:670) 
        at android.hardware.camera2.CameraManager.openCamera(CameraManager.java:638) 
        at androidx.camera.camera2.internal.compat.CameraManagerCompatApi28Impl.openCamera(CameraManagerCompatApi28Impl.java:70) 
        at androidx.camera.camera2.internal.compat.CameraManagerCompat.openCamera(CameraManagerCompat.java:185) 
        at androidx.camera.camera2.internal.Camera2CameraImpl.openCameraDevice(Camera2CameraImpl.java:871) 
        at androidx.camera.camera2.internal.Camera2CameraImpl.openInternal(Camera2CameraImpl.java:236) 
        at androidx.camera.camera2.internal.Camera2CameraImpl.tryAttachUseCases(Camera2CameraImpl.java:691) 
        at androidx.camera.camera2.internal.Camera2CameraImpl.lambda$attachUseCases$10$Camera2CameraImpl(Camera2CameraImpl.java:649) 
        at androidx.camera.camera2.internal.-$$Lambda$Camera2CameraImpl$_NFNV64YCFFY0Tn3VRiyE3Ss3S0.run(Unknown Source:4) 
        at androidx.camera.core.impl.utils.executor.SequentialExecutor$QueueWorker.workOnQueue(SequentialExecutor.java:230) 
        at androidx.camera.core.impl.utils.executor.SequentialExecutor$QueueWorker.run(SequentialExecutor.java:172) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 
        at java.lang.Thread.run(Thread.java:764) 

根據日志，我沒有插入相機權限，但我這樣做了。 也許我錯過了其他權限？

Answer 1

根據 Husayn 和 Shark 的建議，我已經解決了這個問題。 任何具有 Android 6 或更高版本 (API 23+) 的設備都需要運行時權限。

檢查用戶是否授予了相機權限。 否則，請請求該許可。 在調用 CameraX 代碼之前，在onCreate()方法中插入以下代碼：

if (checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.CAMERA}, CAMERA_REQUEST);
}

其中CAMERA_REQUEST是一個常量。 這是一個例子：

private static final int CAMERA_REQUEST = 100;

然后，它會出現一個對話框，用戶可以在其中允許或拒絕權限。 我們可以通過以下方法查看結果：

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == CAMERA_REQUEST) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "CameraX permission granted", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "CameraX permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }