即使使用線程池，Android Cordova Plugin也會鎖定UI線程

Question

我已經編寫了一個Cordova插件，用於在Android上對圖像進行圖像大小調整，但UI會在大量圖像（超過100個）翻牌停止。我在theadPool上執行所有的調整大小，最初只是一個可運行的，但在閱讀Cordova Plugins and Thread Blocking的博客文章後，我切換到了一個外部類來完成這項工作。但是我仍然得到：

W/PluginManager﹕ THREAD WARNING: exec() call to ImageStore.getImage blocked the main thread for 91ms. Plugin should use CordovaInterface.getThreadPool(). 

對於調整每個圖像，調用看起來是這樣的：

private boolean getImage(final JSONArray args, final CallbackContext callbackContext) throws JSONException { 

    JSONObject argObject = args.getJSONObject(0); 

    int photoId = argObject.getInt("photoId"); 
    final PhotoData photoData = mPhotos.get(photoId); 

    cordova.getThreadPool().execute(new GetImageRunnable(photoData, callbackContext)); 

    return true; 
} 

凡GetImageRunnable沒有聯繫，只是傳入的photoData對象主要插件有什麼方法可以查看導致減速或阻塞主線程的原因？

Answer 1

你可以給下面的代碼一試，它使用了最少的AsyncTask運行GetImageRunnable：

private boolean getImage(final JSONArray args, final CallbackContext callbackContext) throws JSONException { 

    JSONObject argObject = args.getJSONObject(0); 

    int photoId = argObject.getInt("photoId"); 
    final PhotoData photoData = mPhotos.get(photoId); 

    (new MyTask(photoData, callbackContext)).execute(); 

    return true; 
} 

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

    private PhotoData mPhotoData; 
    private CallbackContext mCallbackContext; 

    public MyTask(PhotoData photoData, CallbackContext callbackContext) { 
     mPhotoData = photoData 
     mCallbackContext = callbackContext; 
    } 

    protected Void doInBackground(Void... v) { 
     (new GetImageRunnable(photoData, callbackContext)).run(); 
     return null; 
    } 

    protected void onProgressUpdate(Void... v) { 
    } 

    protected void onPostExecute(Void v) { 
    } 
} 

它留下的東西雖然不理想;該回調將在後臺線程中運行。如果你需要在主線程中運行，您可以掩蓋初始CallbackContext（這是不是最後一次），並將結果傳遞到原來的onPostExecute：

private boolean getImage(final JSONArray args, final CallbackContext callbackContext) throws JSONException { 

    JSONObject argObject = args.getJSONObject(0); 

    int photoId = argObject.getInt("photoId"); 
    final PhotoData photoData = mPhotos.get(photoId); 

    (new MyTask(photoData, callbackContext)).execute(); 

    return true; 
} 

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

    private PhotoData mPhotoData; 
    private CallbackContext mCallbackContext; 
    private CallbackContext mMaskedContext; 

    public MyTask(PhotoData photoData, CallbackContext callbackContext) { 
     mPhotoData = photoData 
     mCallbackContext = callbackContext; 
     mMaskedContext = new MyCallbackContext(callbackContext); 
    } 

    protected Void doInBackground(Void... v) { 
     (new GetImageRunnable(photoData, mMaskedContext)).run(); 
     return null; 
    } 

    protected void onProgressUpdate(Void... v) { 
    } 

    protected void onPostExecute(Void v) { 
     mCallbackContext.sendPluginResult(mMaskedContext.getPluginResult()); 
    } 
} 

class MyCallbackContext extends CallbackContext { 
    private CallbackContext mOriginalContext; 
    private PluginResult mPluginResult; 

    public MyCallbackContext(CallbackContext originalContext) { 
     super(originalContext.getCallbackId(), null); 
     mOriginalContext = originalContext; 
    } 

    public void sendPluginResult(PluginResult pluginResult) { 
     mPluginResult = pluginResult; 
    } 

    public pluginResult getPluginResult() { 
     return mPluginResult; 
    } 
} 

注：這是不是經過測試，代碼只是爲了說明這些想法。