Question

虽然我在网上查了很多参考文献，但我仍然找不到问题。似乎ProgressDialog看起来不错，但每当我想要更新进度时，在onProgressUpdate中它的实例总是为空。

这是我的AsyncTask：

package com.async_tasks;

public class UploadTask extends AsyncTask<Void,Integer,Void> implements Serializable {        
    private static final String TAG = UploadTask.class.getSimpleName();
    private ConnectionToServer _connectionToServer;
    private TransferDetails _td;
    private Activity _activity;
    private ProgressDialog _progDialog;
    private UploadTask _taskInstance;

    public UploadTask(Activity activity, ConnectionToServer connectionToServer, TransferDetails td) {

        _activity = activity;
        _connectionToServer = connectionToServer;
        _td = td;
        _taskInstance = this;
    }

    @Override
    protected void onPreExecute() {

        _progDialog = new ProgressDialog(_activity);
        String cancel = _context.getResources().getString(R.string.cancel);

        _progDialog.setCancelable(false);
        _progDialog.setTitle(_context.getResources().getString(R.string.uploading));
        _progDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        _progDialog.setProgress(0);
        _progDialog.setMax(100);
        _progDialog.setButton(DialogInterface.BUTTON_NEGATIVE, cancel, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                _taskInstance.cancel(true);
            }
        });

        _progDialog.show();

    }

    @Override
    protected Void doInBackground(Void... voids) {

        //uploading file ...
                float percent = (float) (fileSize - bytesToRead) / fileSize * 100;
                publishProgress((int)percent);                   
            }

        }
         catch (IOException e) {
               // Handling exception
        } finally {

            if(bis!=null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            clearMembers();

            }
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... progress) {

        if(_progDialog!=null) { // <<------------ I suspect for some reason this is always false, as _progDialog is always null - But why?!
            _progDialog.incrementProgressBy(progress[0]);
        }
    }

    @Override
    protected void onPostExecute(Void result)    {

        //The task is complete, clear members
        clearMembers();
    }

    private void clearMembers() {

        _activity = null;
        if(_progDialog!=null) {
            _progDialog.dismiss();
            _progDialog = null;
        }
    }
}

这是来自MainActivity的电话：

TransferDetails td = (TransferDetails) report.data();
ConnectionToServer conn  = StorageServerProxyService.getConn();
UploadTask uploadTask = new UploadTask(MainActivity.this, conn, td);
uploadTask.execute();

Answer 1

修改onPreExecute（）方法，如下所示：

@Override
    protected void onPreExecute() {

 progDialog = new ProgressDialog(ActivityName.this);
        String cancel = _context.getResources().getString(R.string.cancel);

        _progDialog.setCancelable(false);
        _progDialog.setTitle(_context.getResources().getString(R.string.uploading));
        _progDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        _progDialog.setProgress(0);
        _progDialog.setMax(100);
        _progDialog.setButton(DialogInterface.BUTTON_NEGATIVE, cancel, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                _taskInstance.cancel(true);
            }
        });

        _progDialog.show();

    }

AsyncTask里面的ProgressDialog没有显示进度

1 个答案: