相机预览未重新启动

Question

我正在研究安卓中的相机代码来拍照并将其保存在手机上。它从手机摄像头拍摄照片并将其保存在存储卡上。唯一的问题是拍照后相机预览没有重新启动。

我无法找出解决方案。代码如下。需要建议 . . .我的项目中有两个类。 。 。

相机活动类

public class CameraActivity extends Activity 
{
  private static final String TAG = "CameraDemo";
  Preview preview; 
  Button buttonClick; 
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    preview = new Preview(this); 
    ((FrameLayout) findViewById(R.id.preview)).addView(preview); 
    buttonClick = (Button) findViewById(R.id.buttonClick);
    buttonClick.setOnClickListener(new OnClickListener() {
      public void onClick(View v) { 
        preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback);    
      }
    });
    Log.d(TAG, "onCreate'd");
  }
  // Called when shutter is opened
  ShutterCallback shutterCallback = new ShutterCallback() { 
    public void onShutter() {
      Log.d(TAG, "onShutter'd");
    }
  };
  // Handles data for raw picture
  PictureCallback rawCallback = new PictureCallback() {
    public void onPictureTaken(byte[] data, Camera camera) {
      Log.d(TAG, "onPictureTaken - raw");
    }
  };
  // Handles data for jpeg picture
  PictureCallback jpegCallback = new PictureCallback() { 
    public void onPictureTaken(byte[] data, Camera camera) {
      FileOutputStream outStream = null;
      try {
        // Write to SD Card
        outStream = new FileOutputStream(String.format("/sdcard/DCIM/queries.jpg",
            System.currentTimeMillis()));
        outStream.write(data);
        outStream.close();
        Log.d(TAG, "onPictureTaken - wrote bytes: " + data.length);
      } catch (FileNotFoundException e) { 
        e.printStackTrace();
      } catch (IOException e) {
        e.printStackTrace();
      } finally {
      }
      Log.d(TAG, "onPictureTaken - jpeg");
    }
  };
}

预览类

class Preview extends SurfaceView implements SurfaceHolder.Callback{ 
  private static final String TAG = "Preview";
  SurfaceHolder mHolder;  // <2>
  public Camera camera; // <3>
  Preview(Context context) {
    super(context);
    // Install a SurfaceHolder.Callback so we get notified when the
    // underlying surface is created and destroyed.
    mHolder = getHolder();  // <4>
    mHolder.addCallback(this);  // <5>
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); // <6>
  }
  // Called once the holder is ready
  public void surfaceCreated(SurfaceHolder holder) {  // <7>
    // The Surface has been created, acquire the camera and tell it where
    // to draw.
    camera = Camera.open(); // <8>
    try {

        Camera.Parameters parameters = camera.getParameters();
        parameters.set("orientation", "landscape");
        camera.setParameters(parameters);
        camera.setPreviewDisplay(holder);  
        camera.setPreviewCallback(new PreviewCallback() { 
        // Called for each frame previewed
        public void onPreviewFrame(byte[] data, Camera camera) {  
          Log.d(TAG, "onPreviewFrame called at: " + System.currentTimeMillis());
          Preview.this.invalidate();  
        }
      });
    } catch (IOException e) { 
      e.printStackTrace();
    }
  }
  // Called when the holder is destroyed
  public void surfaceDestroyed(SurfaceHolder holder) { 
    //Log.d(TAG,"Stopping preview in SurfaceDestroyed().");
    camera.setPreviewCallback(null);
    camera.stopPreview();
    camera.release();
    camera = null;           
  }
  // Called when holder has changed
  public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { 
    camera.startPreview();
  }
}

Answer 1

Android API Guide中关于相机的文章也遇到了同样的问题。我可以在拍照后通过添加另外两个内容来恢复预览，如下所示：

1） 在AndroidManifest.xml文件中添加外部存储权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2）通过调用camera.startPreview()再次开始预览。在您的代码中：

...
Log.d(TAG, "onPictureTaken - jpeg");
camera.startPreview();
....

我相信你一定能以同样的方式让你的工作。

Answer 2

在 onPicturePhoto中再次启动 CAMERAACTIVITY 像这样拍摄：

// Handles data for jpeg picture
  PictureCallback jpegCallback = new PictureCallback() { 
    public void onPictureTaken(byte[] data, Camera camera) {
      FileOutputStream outStream = null;
      try {
        // Write to SD Card
        outStream = new FileOutputStream(String.format("/sdcard/DCIM/queries.jpg",
            System.currentTimeMillis()));
        outStream.write(data);
        outStream.close();
        Log.d(TAG, "onPictureTaken - wrote bytes: " + data.length);
      } catch (FileNotFoundException e) { 
        e.printStackTrace();
      } catch (IOException e) {
        e.printStackTrace();
      } finally {
        camera.release();
        camera = null;
        startActivity(new Intent(CAMERAACTIVITY.this, CAMERAACTIVITY.class));
        finish();
      }
      Log.d(TAG, "onPictureTaken - jpeg");
    }
  };

如果需要，您还可以使用 Thread.sleep（2000）; 这样，捕获的图像将显示 2 秒钟，然后再次开始相机活动。

Answer 3

add线程睡眠（2000）;camera.startPreview（）;

这样相机将显示捕获的图像 2 秒并重新启动相机。