Question

我的AsyncTask的progressDialog没有显示。它似乎是正确的，但它不显示对话框。内部的操作完美但似乎忽略了onPreExecute()和onPostExecute()方法..

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

    int appPosition;
    ProgressDialog mProgressDialog = new ProgressDialog(getActivity());


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

        mProgressDialog.setTitle("Copy apk");
        mProgressDialog.setMessage("Copying...");
        mProgressDialog.setIndeterminate(false);
        mProgressDialog.show();
    }



    @Override
    protected Void doInBackground(Void... apks) {
        final File customfolder = new File(Environment.getExternalStorageDirectory().toString()+File.separator+"HazyApkBackup");
        if(!customfolder.exists()){
            customfolder.mkdirs();
        }
        try
        {

            vacca = getActivity().getPackageManager().getApplicationInfo(app.getPackageName(), packageManager.GET_META_DATA).sourceDir.toString();
            //Toast.makeText(getActivity(), "Boh "+vacca, Toast.LENGTH_SHORT).show();
            process = Runtime.getRuntime().exec("cp " + vacca + " " + customfolder);
            //Toast.makeText(getActivity(), "Apk copied in "+customfolder, Toast.LENGTH_SHORT).show();
        }
        catch (PackageManager.NameNotFoundException | IOException e)
        {
            Toast.makeText(getActivity(), "Sorry, the apk was not copied correctly", Toast.LENGTH_SHORT).show();
        }       

        return null;
        }

    @Override
    protected void onPostExecute(Void result) {
    super.onPostExecute(result);

        if(mProgressDialog.isShowing())
        Toast.makeText(getActivity(), "Apk copied in "+customfolder, Toast.LENGTH_SHORT).show();
        mProgressDialog.dismiss();  

    }
}

由于

Answer 1

您的onPreExecute()方法未被调用，因为它的签名不正确。正确的方法没有参数。

@Override
protected void onPreExecute()
{
    ...

Answer 2

onPreExecute()的原型：

@Override
    protected void onPreExecute() {

}

在UI线程上调用onPreExecute()和onPostExecute()方法。最好使用WeakReference来避免将来出现异常。

在AsyncTask中，创建一个WeakReference，如：

private WeakReference<MyActivity> myWeakContext;

然后在onPreExecute()，

MyActivity activity = this.myWeakContext.get();
ProgressDialog mProgressDialog = new ProgressDialog(activity);

AsyncTask在操作期间未显示对话框

2 个答案: