java - 相机预览不起作用 : Error while loading camera

Question

我的应用程序应该包含全屏相机预览。我不知道我的错误在哪里，应用程序启动后很快就关闭了。

这是我的代码:

主要 Activity

    public class MainActivity extends AppCompatActivity{

    private static final String LOG = "MainActivity.java";

    private Camera mCamera;
    private CameraPreview mPreview;

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

    FloatingActionButton fabPref = (FloatingActionButton)        findViewById(R.id.fabPref);
    fabPref.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

        }
    });

    FloatingActionButton fabPhoto = (FloatingActionButton) findViewById(R.id.fabPhoto);
    fabPhoto.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

        }
    });

    FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);


    if(checkCameraHardware(this)==true){
        Log.e("CAMERA", "vorhanden");


        // Create an instance of Camera
        mCamera = getCameraInstance();
        // Create our Preview view and set it as the content of our activity.
        mPreview = new CameraPreview(this, mCamera);
        preview.addView(mPreview);

    }else{
        Log.e("CAMERA", "nicht vorhanden");
    }

    }
    private boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
        return true;
    } else {
        return false;
    }
    }

public Camera getCameraInstance(){
    Camera c = null;
    try {
        releaseCameraAndPreview();
        c = Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK); // attempt to get a Camera instance
        Log.e(LOG, "CameraInstance: " + c + " RUNS");
    }
    catch (Exception e){
        Log.e(LOG, "Camera not available");
        Log.e(LOG, "CameraInstance: " + c);
    }
    Log.e(LOG, "CameraInstance: " + c);

    return c; // returns null if camera is unavailable

}

private void releaseCameraAndPreview() {
    if (mCamera != null) {
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }
}
    }

这是我的 CameraPreview 的代码:

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

private static final String TAG = "CameraPreview.java";

private SurfaceHolder mHolder;
private Camera mCamera;

public CameraPreview(Context context, Camera camera) {
    super(context);
    mCamera = camera;

    // Install a SurfaceHolder.Callback so we get notified when the
    // underlying surface is created and destroyed.
    mHolder = getHolder();
    mHolder.addCallback(this);
    // deprecated setting, but required on Android versions prior to 3.0
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

public void surfaceCreated(SurfaceHolder holder) {
    // The Surface has been created, now tell the camera where to draw the preview.
    try {
        mCamera.setPreviewDisplay(holder);
        mCamera.startPreview();
    } catch (IOException e) {
        Log.d(TAG, "Error setting camera preview: " + e.getMessage());
    }
}

public void surfaceDestroyed(SurfaceHolder holder) {
    // empty. Take care of releasing the Camera preview in your activity.
}

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
    // If your preview can change or rotate, take care of those events here.
    // Make sure to stop the preview before resizing or reformatting it.

    if (mHolder.getSurface() == null){
        // preview surface does not exist
        return;
    }

    // stop preview before making changes
    try {
        mCamera.stopPreview();
    } catch (Exception e){
        // ignore: tried to stop a non-existent preview
    }

    // set preview size and make any resize, rotate or
    // reformatting changes here

    // start preview with new settings
    try {
        mCamera.setPreviewDisplay(mHolder);
        mCamera.startPreview();

    } catch (Exception e){
        Log.d(TAG, "Error starting camera preview: " + e.getMessage());
    }
}
}

这是运行应用程序后我的 LogCat:

2-16 19:54:06.621 13572-13572/de.aintlarry.shotanalysis I/art: Late-enabling -Xcheck:jni 
12-16 19:54:06.622 13572-13572/de.aintlarry.shotanalysis I/art: VMHOOK: rlim_cur : 0 pid:13572 
12-16 19:54:06.717 13572-13572/de.aintlarry.shotanalysis W/System: ClassLoader referenced unknown path: /data/app/de.aintlarry.shotanalysis-2/lib/arm64 
12-16 19:54:06.834 13572-13572/de.aintlarry.shotanalysis E/CAMERA: vorhanden 
12-16 19:54:06.847 13572-13572/de.aintlarry.shotanalysis W/CameraBase: An error occurred while connecting to camera: 0 
12-16 19:54:07.149 13572-13572/de.aintlarry.shotanalysis W/CameraBase: An error occurred while connecting to camera: 0 
12-16 19:54:07.450 13572-13572/de.aintlarry.shotanalysis W/CameraBase: An error occurred while connecting to camera: 0 
12-16 19:54:07.751 13572-13572/de.aintlarry.shotanalysis W/CameraBase: An error occurred while connecting to camera: 0 
12-16 19:54:08.052 13572-13572/de.aintlarry.shotanalysis W/CameraBase: An error occurred while connecting to camera: 0 
12-16 19:54:08.352 13572-13572/de.aintlarry.shotanalysis I/Camera2Mode: fail 
12-16 19:54:08.352 13572-13572/de.aintlarry.shotanalysis E/MainActivity.java: Camera not available 
12-16 19:54:08.352 13572-13572/de.aintlarry.shotanalysis E/MainActivity.java: CameraInstance: null 
12-16 19:54:08.352 13572-13572/de.aintlarry.shotanalysis E/MainActivity.java: CameraInstance: null 
12-16 19:54:08.430 13572-13621/de.aintlarry.shotanalysis I/Adreno: QUALCOMM build : 8e7809e, Ic2ca81afa7 
Build Date : 09/18/15 
OpenGL ES Shader Compiler Version: XE031.05.13.02 
Local Branch : 
Remote Branch : refs/tags/AU_LINUX_ANDROID_PRIVATE_REDFOX64_MBR_RB1.05.01.01.003.020 
Remote Branch : NONE 
Reconstruct Branch : NOTHING 
12-16 19:54:08.481 13572-13572/de.aintlarry.shotanalysis E/AndroidRuntime: FATAL EXCEPTION: main 
Process: de.aintlarry.shotanalysis, PID: 13572 
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.Camera.setPreviewDisplay(android.view.SurfaceHolder)' on a null object reference 
at de.aintlarry.shotanalysis.CameraPreview.surfaceCreated(CameraPreview.java:33) 
at android.view.SurfaceView.updateWindow(SurfaceView.java:582) 
at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:177) 
at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944) 
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2140) 
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1162) 
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6229) 
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:873) 
at android.view.Choreographer.doCallbacks(Choreographer.java:676) 
at android.view.Choreographer.doFrame(Choreographer.java:606) 
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:859) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:168) 
at android.app.ActivityThread.main(ActivityThread.java:5781) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687) 
12-16 19:54:10.562 13572-13572/de.aintlarry.shotanalysis D/Process: killProcess, pid=13572 
12-16 19:54:10.571 13572-13572/de.aintlarry.shotanalysis D/Process: com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException:113 java.lang.ThreadGroup.uncaughtException:693 java.lang.ThreadGroup.uncaughtException:69

有人知道问题所在吗？我已经尝试了我找到的所有建议。

Answer 1

请更改此设置

public void surfaceCreated(SurfaceHolder holder) {
    // The Surface has been created, now tell the camera where to draw the preview.
    try {
        mCamera.setPreviewDisplay(holder);
        mCamera.startPreview();
    } catch (IOException e) {   //This catch block does not handle NullPointers
        Log.d(TAG, "Error setting camera preview: " + e.getMessage());
    }
}

到此

public void surfaceCreated(SurfaceHolder holder) {
    // The Surface has been created, now tell the camera where to draw the preview.
    try {
        mCamera.setPreviewDisplay(holder);
        mCamera.startPreview();
    } catch (Exception e) { //This catch block does handle NullPointers
        Log.d(TAG, "Error setting camera preview: " + e.getMessage());
    }
}

您使用的 catch block 太窄，无法捕获 null 的 mCamera 对象。这将防止崩溃，但您还应该检查为什么 mCamera 在那里为空以及它是否可以/应该为空。然而，它完全有可能只是尚未初始化，并且将在以后的调用中:-)