ProgressDialog在执行任务时未显示

Question

我有一个备份例程,可以将所有内容从一个文件夹复制到外部SD卡,完美无缺.我正在尝试获得一个很好的弹出对话框,显示它正在运行但它没有显示.甚至没有尝试运行(但备份确实完成).

这是我目前的代码:

public void doBackup(View view) throws IOException{
    ProgressDialog pd = new ProgressDialog(this);
    pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    pd.setMessage("Running backup. Do not unplug drive");
    pd.setIndeterminate(true);
    pd.setCancelable(false);
    pd.show();
    File source = new File("/mnt/extSdCard/DirectEnquiries"); 
    File dest = new File("/mnt/UsbDriveA/Backup");
    copyDirectory(source, dest);
    pd.dismiss();
}

Answer 1

您在a Thread或with中运行长时间运行的任务AsyncTask.那么你的ProgressDialog意志就会出现.

做类似的事情:

public void doBackup(View view) throws IOException{
    final ProgressDialog pd = new ProgressDialog(this);
    pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    pd.setMessage("Running backup. Do not unplug drive");
    pd.setIndeterminate(true);
    pd.setCancelable(false);
    pd.show();
    Thread mThread = new Thread() {
        @Override
        public void run() {
            File source = new File("/mnt/extSdCard/DirectEnquiries"); 
            File dest = new File("/mnt/UsbDriveA/Backup");
            copyDirectory(source, dest);
            pd.dismiss();
        }
    };
    mThread.start();
}