捕獲圖像後調用StartPreview（）的最佳方式是什麼？

Question

一旦調用Camera.takePicture（），我的預覽將停止更新，如文檔中所述。檢測圖像捕獲過程完成並調用startPreview（）使其再次開始更新的最佳方法是什麼？

呼叫不能被放置在任何傳遞給takePicture的回調，根據文檔，因爲他們應該在我引用這一切都回來了。

我目前最好的猜測是建立一個處理程序和發佈延遲的Runnable，將其從JPEG回調（或取其最最後定義的回調返回）。

Answer 1

你應該從的AsyncTask（或線程），然而AsyncTaks的是更容易的選擇中啓動mCamera.takePicture。

一個非常簡單的實現（這當然可以被修改）是：

稱爲拍攝照片的方法

/** 
* Execute the AsyncTask that will handle the preview of the captured photo. 
*/ 
public void takePicture() { 
    TakePictureTask takePictureTask = new TakePictureTask(); 
    takePictureTask.execute(); 
} 

的的AsyncTask子類

/** 
* A pretty basic example of an AsyncTask that takes the photo and 
* then sleeps for a defined period of time before finishing. Upon 
* finishing, it will restart the preview - Camera.startPreview(). 
*/ 

private class TakePictureTask extends AsyncTask<Void, Void, Void> { 

    @Override 
    protected void onPostExecute(Void result) { 
     // This returns the preview back to the live camera feed 
     mCamera.startPreview(); 
    } 

    @Override 
    protected Void doInBackground(Void... params) { 
     mCamera.takePicture(null, null, mPictureCallback); 

     // Sleep for however long, you could store this in a variable and 
     // have it updated by a menu item which the user selects. 
     try { 
      Thread.sleep(3000); // 3 second preview 
     } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 

     return null; 
    } 

} 

PictureCallback字段

private PictureCallback mPictureCallback = new PictureCallback() { 

    @Override 
    public void onPictureTaken(byte[] data, Camera camera) { 
     File file = null; 

     // Check whether the media is mounted with read/write permission. 
     if (Environment.MEDIA_MOUNTED.equals(
       Environment.getExternalStorageState())) { 
      file = getOutputMediaFile(); 
     } 

     if (file == null) { 
      Log.d(TAG, "Error creating media file, check storage persmissions!"); 
      return; 
     } 

     try { 
      FileOutputStream fileOutputStream = new FileOutputStream(file); 
      fileOutputStream.write(data); 
      fileOutputStream.close(); 
     } catch (FileNotFoundException e) { 
      Log.d(TAG, "File not found: " + e.getMessage()); 
     } catch (IOException e) { 
      Log.d(TAG, "Error accessing file: " + e.getMessage()); 
     } 
    } 
}; 

Answer 2

由於PictureCallback在一個單獨的線程啓動反正（它不會鎖定用戶界面），你不需要使用的AsyncTask調用捕獲。

有兩種方式，做你想做的事，最簡單的是：

mCamera.startPreview(); //preview has to be started before you can take a picture 
mCamera.takePicture(null, null, mPictureCallback); //take a picture 

private PictureCallback mPictureCallback = new PictureCallback() { 
    @Override 
    public void onPictureTaken(byte[] data, Camera camera) { 
     camera.startPreview(); //once your camera has successfully finished 
           //its capture it's safe to restart the preview 
     ... //anything else you want to do to process that image 
    } 
} 

第二是使用匿名函數，如：

mCamera.takePicture(null, null, new PictureCallback(){ 
    ... 
}); 

兩個有他們的用途，取決於您的需求。