Question

我收到NullPointerException错误，它引用了Camera.Parameters：

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int w,
        int h) {
    // TODO Auto-generated method stub
        Log.e(TAG, "surfaceChanged");

        if (mPreviewRunning) {
             mCamera.stopPreview();
             mPreviewRunning = false;
             Log.e(TAG, "stopPeview");
            }
        Camera.Parameters p = mCamera.getParameters();
        Log.e(TAG, "paarameters");

        p.setPreviewSize(w, h);

        mCamera.setParameters(p);  
        Log.e(TAG, " set parameters");
            try {
                mCamera.setPreviewDisplay(holder);

                Log.e(TAG, "setPreview");
                } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            mCamera.startPreview();
            mPreviewRunning = true;
    }

有人能告诉我上面代码中的错误是什么。

我将不得不再次测试它以获取日志，但这是整个代码。我确实改变了清单。

public class Picture extends Activity implements SurfaceHolder.Callback{

private String TAG;
private LayoutInflater mInflater = null;
private Camera mCamera;
boolean mPreviewRunning = false;
private SurfaceHolder mSurfaceHolder;
private SurfaceView mSurfaceView;
Button takepicture;
byte[] tempdata;

@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    getWindow().setFormat(PixelFormat.TRANSLUCENT);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

    setContentView(R.layout.camera_surface);

    mCamera = getCameraInstance (); 

    mSurfaceView = (SurfaceView)findViewById(R.id.surface_camera);
    mSurfaceHolder = mSurfaceView.getHolder();
    mSurfaceHolder.addCallback(this);
    mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    mInflater = LayoutInflater.from(this);
    View overView = mInflater.inflate(R.layout.cameraoverlay, null);
    this.addContentView(overView, new LayoutParams(LayoutParams.FILL_PARENT,
            LayoutParams.FILL_PARENT));

    takepicture = (Button) findViewById(R.id.button);
    takepicture.setOnClickListener(new OnClickListener() {

    public void onClick(View view) {
                mCamera.takePicture(shutterCallback, mPictureCallback,
                jpegCallback);
        }
    });

}

private Camera getCameraInstance() {
    // TODO Auto-generated method stub
    Camera mCamera = null;
    try {
        mCamera = Camera.open();
    } catch (Exception e) {

    }
    return mCamera;
}


ShutterCallback shutterCallback = new ShutterCallback() {
    @Override
    public void onShutter() {}
};
    PictureCallback mPictureCallback = new PictureCallback() {
    public void onPictureTaken(byte[] data, Camera c) {}
};
PictureCallback jpegCallback = new PictureCallback() {
        public void onPictureTaken(byte[] data, Camera c) {
            if(data != null) {
                tempdata=data;
                done();
            }
        }
    };

    void done(){
        Bitmap bm = BitmapFactory.decodeByteArray(tempdata, 0, tempdata.length);
        String url = Images.Media.insertImage(getContentResolver(),
                bm, null, null);        
        bm.recycle();
        Bundle bundle = new Bundle();
        if(url!=null) {
            bundle.putString("url", url);

            Intent mIntent = new Intent();
            mIntent.putExtras(bundle);
            setResult(RESULT_OK, mIntent);          
        } else {
            Toast.makeText(this, "Picture can not be saved",
                            Toast.LENGTH_SHORT).show();
        }
        finish();
    }
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int w,
        int h) {
    // TODO Auto-generated method stub
        Log.e(TAG, "surfaceChanged");

        if (mPreviewRunning) {
             mCamera.stopPreview();
             mPreviewRunning = false;
             Log.e(TAG, "stopPeview");
            }
        Camera.Parameters p = mCamera.getParameters();
        Log.e(TAG, "paarameters");

        p.setPreviewSize(w, h);

        mCamera.setParameters(p);  
        Log.e(TAG, " set parameters");
            try {
                mCamera.setPreviewDisplay(holder);

                Log.e(TAG, "setPreview");
                } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            mCamera.startPreview();
            mPreviewRunning = true;
    }   

@Override
public void surfaceCreated(SurfaceHolder holder) {
    Log.e(TAG, "surfaceCreated");
    try {
    mCamera = Camera.open();
    Log.e(TAG, "camera open");

    } catch(Exception e) {}

    }



@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    Log.e(TAG, "surfaceDestroyed");

    mCamera.stopPreview();  
    mPreviewRunning = false;
    mCamera.release();        // release the camera for other applications
    mCamera = null;

}
}

此外，引用的日志行是行：Camera.Parameters p = mCamera.getParameters（）;

Answer 1

看起来mCamera是null ...你初始化了吗？（mCamera = Camera.open();）

请参阅docs获取与拍照相关的清单

Answer 2

在表现文件::

中添加以下三行

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

要使用此课程拍摄照片，请使用以下步骤：

1）从open（int）获取Camera实例。

2）使用getParameters（）获取现有（默认）设置。

3）如有必要，修改返回的Camera.Parameters对象并调用 setParameters（Camera.Parameters）。

4）如果需要，请调用setDisplayOrientation（int）。

5）重要事项：将完全初始化的SurfaceHolder传递给setPreviewDisplay（SurfaceHolder）。没有表面，相机将无法开始预览。

6）重要提示：调用startPreview（）开始更新预览曲面。必须先开始预览才能拍照。

7）如果需要，可以调用takePicture（Camera.ShutterCallback，Camera.PictureCallback，Camera.PictureCallback，Camera.PictureCallback）来捕捉照片。等待回调提供实际的图像数据。

8）拍照后，预览显示将停止。要拍摄更多照片，请先再次调用startPreview（）。

9）调用stopPreview（）以停止更新预览表面。

10）重要事项：调用release（）以释放相机以供其他应用程序使用。应用程序应立即在onPause（）中释放相机（并在onResume（）中重新打开（））。

Answer 3

有许多解决方案，但这是一个简单，便宜的选项，对我有用：

try{
   mCamera.autoFocus(autoFocusCB); //Or whatever part of code that crashes
   }
catch(Exception e){
   Log.v("joshtag","THIS PHONE DOES NOT SUPPORT AUTOFOCUS!!"); //a warning, popup, whatever
   }

瞧！陷阱已停用。

当然，不要忘记明显的权限......

在摄像机设置参数上获取空指针异常

3 个答案: