Question

我在存储中有复制文件的功能。当我单击以复制Button时，将执行方法复制操作。这个方法如下：

    public void actionCopy() {
       Dialog dialog = new Dialog(this);
       dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
       dialog.setContentView(R.layout.progress_layout);

       TextView progressTitle = (TextView) dialog.findViewById(R.id.progress_title);
       progressTitle.setText("Copying...");
       final ProgressBar progressBar = (ProgressBar)  dialog.findViewById(R.id.progress_bar);
       progressBar.setMax(listData.size());
       progressBar.setProgress(0);

       dialog.show();

       for(int i = 0; i < listData.size(); i++) {
          String value = new CopyDataUtils(listData.get(i)).execute().get();
          progressBar.setProgress(i + 1);
          Log.i(TAG, value);
    }
 }

CopyDataUtils AsyncTask：

public class CopyDataUtils extends AsyncTask<Void, Void, String> {

    private DataItem item;

    public CopyDataUtils(DataItem item) {
        this.item = item;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(Void... params) {

        //...code copy file here
        return ...;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
    }
}

所以我的问题是：当actionCopy执行时，我想要显示对话框。但没有发生。执行for(..)后，显示对话框。出了什么问题？在执行多线程复制数据之前是否有关于show对话框的建议？对不起，我的英文不好！

**更新：我尝试将对话框添加到AsyncTask并将其显示在方法onPreExecute中。但没有任何改变。

Answer 1

问题是new CopyDataUtils(listData.get(i)).execute().get();。 It blocks the UI thread and waits if necessary for the computation to complete, and then retrieves its result

您使用AsyncTask和对话框的方式完全错误。您应该将这些代码移至AsynTask。在onPreexecute上，您应该显示对话框。 doInbackground你做任务并在onPostexecute隐藏对话。

Answer 2

你应该在Asynctask的onPreEcecute（）中显示进度条

   public void onPreExecute()
        {
            progressDialog = new ProgressDialog(activity);
            progressDialog.setMessage("your content");
            progressDialog.setMax(listData.size());
            progressDialog.setProgress(0);

       for(int i = 0; i < listData.size(); i++) {
          String value = new CopyDataUtils(listData.get(i)).execute().get();

          Log.i(TAG, value);


            progressDialog.show();
        }


 @Override
    protected String doInBackground(Void... params) {


        return ...;
    }

 @Override
    public void onPostExecute(String s)
    {
        progressBar.setProgress(i + 1);
    }

Answer 3

您应该将ProgressBar作为全局变量，然后更新AsyncTask onPostExcute()中的进度

public void YouActiviy() {
         ProgressBar progressBar;
         int i = 0;
         public onCreate(){
            ....
         }

         public void actionCopy() {
           ...
           progressBar = (ProgressBar)  dialog.findViewById(R.id.progress_bar);
           ...
           dialog.show();
           for(int i = 0; i < listData.size(); i++) {
              new CopyDataUtils(listData.get(i)).execute();
              //progressBar.setProgress(i + 1);
           }
         }

         public class CopyDataUtils extends AsyncTask<Void, Void, String> {
             ...
              @Override
              protected void onPostExecute(String s) {
                  // update your progressbar here
                   progressBar.setProgress(i++);
                  super.onPostExecute(s);
              }
         }
    }

为方便起见，您可以按照tutorial这样与AsyncTask

一起使用ProgressBar的正确方法

希望这个帮助

Answer 4

你应该在onProgressUpdate（）中设置进度，试试这个：

protected ProgressDialog mProgressDialog;

private class copyData extends AsyncTask<String, Integer, String> {

protected String doInBackground(Void... params) {
    //copy data here
    return ...;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();

    mProgressDialog = new ProgressDialog(YourActivity.this);
    mProgressDialog.setMessage("Loading...");
    mProgressDialog.setIndeterminate(true);
    mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    mProgressDialog.setCancelable(true);
    mProgressDialog.show();
}

@Override
protected void onProgressUpdate(Integer... progress) {
    super.onProgressUpdate(progress);
    mProgressDialog.setIndeterminate(false);
    mProgressDialog.setMax(100);
    mProgressDialog.setProgress(progress[0]);
}

protected void onPostExecute(String result) {
    try {
        if ((mProgressDialog != null) && mProgressDialog.isShowing()) {
            mProgressDialog.dismiss();
        }
    } catch (final IllegalArgumentException e) {
        // Handle or log or ignore
    } finally {
        mProgressDialog = null;
    }
    }
 }

无法在onClick中显示对话框

4 个答案: