Android Camera takePicture函数不调用Callback函数

Question

我正在为我的应用程序开发自定义相机 Activity 。 我正在按照此处 Android 开发者网站的说明进行操作: http://developer.android.com/guide/topics/media/camera.html 一切似乎都正常，只是没有调用回调函数并且没有保存图片。这是我的代码:

public class CameraActivity extends Activity {
private Camera mCamera;
private CameraPreview mPreview;
private static final String TAG = "CameraActivity";

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.camera);

    // 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);
    FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
    preview.addView(mPreview);

    Button captureButton = (Button) findViewById(R.id.button_capture);
    captureButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.v(TAG, "will now take picture");
            mCamera.takePicture(null, null, mPicture);
            Log.v(TAG, "will now release camera");
            mCamera.release();
            Log.v(TAG, "will now call finish()");
            finish();
        }
    });        
}

private PictureCallback mPicture = new PictureCallback() {

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        Log.v(TAG, "Getting output media file");
        File pictureFile = getOutputMediaFile();
        if (pictureFile == null) {
            Log.v(TAG, "Error creating output file");
            return;
        }
        try {
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();
        } catch (FileNotFoundException e) {
            Log.v(TAG, e.getMessage());
        } catch (IOException e) {
            Log.v(TAG, e.getMessage());
        }
    }
};

private static File getOutputMediaFile() {
    String state = Environment.getExternalStorageState();
    if (!state.equals(Environment.MEDIA_MOUNTED)) {
        return null;
    }
    else {
        File folder_gui = new File(Environment.getExternalStorageDirectory() + File.separator + "GUI");
        if (!folder_gui.exists()) {
            Log.v(TAG, "Creating folder: " + folder_gui.getAbsolutePath());
            folder_gui.mkdirs();
        }
        File outFile = new File(folder_gui, "temp.jpg");
        Log.v(TAG, "Returnng file: " + outFile.getAbsolutePath());
        return outFile;
    }
}

单击按钮后，我得到日志:“现在将拍照”、“现在将释放相机”和“现在将调用完成”。 Activity 成功完成，但回调函数未在

mCamera.takePicture(null, null, mPicture);

函数(没有来自 mPicture 回调或 getMediaOutputFile 函数的日志)并且在指定的位置没有文件。

有什么想法吗？ :) 非常感谢!

Answer 1

对 mCamera.takePicture() 的调用是异步的。这意味着调用会立即完成，但实际的拍照和处理会在稍后发生。但是，您在从 mCamera.takePicture() 调用返回后立即执行此操作:

Log.v(TAG, "will now release camera");
mCamera.release();
Log.v(TAG, "will now call finish()");
finish();

这意味着在相机有机会实际拍照并给您回电之前，您已经释放了相机资源并完成了 Activity。

您需要将该代码移动到回调方法 onPictureTaken() 中，以便在回调发生后释放资源并完成 Activity。