Question

第二次调用SurfaceHolder.Callback的surfaceCreated方法时，我遇到了相机对象的问题，我的意思是：

我在我的onResume方法中从我的活动中创建了一个对象相机，这很好地显示了预览显示，但是当我的活动停止时，surfaceview被破坏，我必须释放相机对象然后如果我的活动来到onresume android在我的相机对象中抛出了一个nullPointerException。

我不确定为什么会发生这种情况，我发表评论来调试每个方法，看看会发生什么，显然一切都很好，只有在surfaceCreated方法中，相机对象变为空。

这是我的班级：

public class CameraRecord implements SurfaceHolder.Callback{

public static final int BACK_CAMERA = 1;
public static final int FRONT_CAMERA = 2;
//private SurfaceView surface;
private SurfaceHolder holder;
private Camera camera;

public CameraRecord(SurfaceView surface){
//  this.surface = surface;
    holder = surface.getHolder();
    holder.addCallback(this);
    holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    Log.e("CameraRecord","constructor");
}


public void openCamera(int wichCamera) throws Exception {

    if (wichCamera == BACK_CAMERA)
        camera = Camera.open();
    else {
        Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
        int cameraCount = Camera.getNumberOfCameras();

        for (int i = 0; i < cameraCount; i++ ) {
            Camera.getCameraInfo(i, cameraInfo);
            if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT)
                try {
                    camera = Camera.open(i); 
                    Log.e("CameraRecord","camera is CAMERA_FACING_FRONT " + cameraInfo.toString());
                } catch (RuntimeException e) {
                    e.printStackTrace();
                }
        }
    }

    if (camera == null)
        Log.e("CameraRecord","openCamera camera is null");
    else
        Log.e("CameraRecord","openCamera camera is not null");

}

public void start() throws IOException {
    camera.startPreview();
}

public void stop() {
    camera.stopPreview();
    Log.e("CameraRecord","stop camera");
}

public void release() {
    camera.release();
    camera = null;
}




@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    Log.e("CameraRecord", "surfaceChanged");
    try {
        start();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
//      if (holder == null)
//          Log.e("CameraRecord","holder is null");
//      else
//          Log.e("CameraRecord","holder is not null");

    try {
        if (camera == null)
            Log.e("CameraRecord","camera is null");
        else
            Log.e("CameraRecord","camera is not null");

        camera.setPreviewDisplay(holder);
//          start();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    Log.e("CameraRecord", "surfaceDestroyed");
    stop();
    release();
}

}

Answer 1

我遇到了同样的问题。我解决它的方式是在我释放相机的同时在我的SurfaceHolder中调用removeCallbak（）方法（在onPause（）方法上）。我猜你的例子就是

holder.removeCallback(this);

我们的想法是，您不仅要在活动的onPause（）方法上释放相机，还要删除SurfaceHolder上的回调集。如果不这样做，错误将第二次出现，因为回调是对您关联的第一个实例而不是第二个实例进行的。如果你也在onPause（）上删除回调，你应该没有任何问题。

Answer 2

我有这样的问题，在AndroidManifest.xml中添加这3行后，我的应用程序工作

<uses-permission android:name="android.permission.CAMERA" />    
    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.camera.autofocus" />

也许它会帮助你:)。

Answer 3

public void release() {
    camera.release();
    camera = null;
}

这应该是：

public void release() {
   if(camera!=null) camera.release();
    camera = null;
}

第二次执行surfaceCreated方法时，Camera为null

3 个答案: