Android进度对话框 [英] Android progress dialog

问题描述

我的应用程序从互联网中获取一些HTML代码，完成后，将其显示在设备屏幕上。由于这需要大约3-4秒钟的时间，所以屏幕保持黑色，我想使用进度对话框。这是我的代码：

My application fetches some html code from the internet and when done , displays it on the devices screen. Since it takes about 3-4 seconds to do that , in this time the screen stays black , I'd like to use a progress dialog. This is my code :

package com.nextlogic.golfnews;



// ALL THE IMPORTS ....

public class Activity1 extends Activity {

    private ProgressDialog progressDialog;
 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);

        progressDialog = ProgressDialog.show(Activity1.this, "", "Loading...");
        new Thread() 
        {
          public void run() 
          {

             try
               {
                sleep(2000);

          // HERE I'VE PUT ALL THE FUNCTIONS THAT WORK FOR ME
 }
    catch (Exception e)
    {
        Log.e("tag",e.getMessage());
    }
// dismiss the progressdialog   
  progressDialog.dismiss();
 }
}.start();

该程序工作，但不再显示任何内容。我在logcat中有一个错误：

The program works but it doesn't display anything anymore. I have one error in logcat :

Only the original thread that created a view hierarchy can touch its views.

你能帮助我吗？感谢提前。

Could you please help me ? Thanks in advance.

推荐答案

错误是足够明确的。要更新一个可视对象，您必须在主线程内运行更改。一个快速而肮脏的修复可能会调用 runOnUiThread（）中的更新代码。

The error is explicative enough. To update one visual object you must run the changes inside main thread. A quick and dirty fix could be calling the update code inside runOnUiThread().

然而，在你的情况下，我将使用一个 AsyncTask 下载并更新进度条的进度。任务具有在UI线程结束时运行的属性（因此您可以更新其中的视图，例如关闭进度对话框）

However in your case I would use an AsyncTask to download and update the progress of the progress bar. The task has the property to run on UI thread when it ends (so you can update the views there, such as dismissing the progress dialog)

这里是一个使用AsyncTask显示下载进度对话框的例子。

Here is an example how to use an AsyncTask to display a download progress dialog.

更新

Stackoverflow已经有你所有问题的答案。 这里是一个AsyncTask的例子来下载一些内容并显示下载进度。只需你想要的。

Stackoverflow already has the answers to all your question. Here is an example of an AsyncTask to download some content and display the download progress. Just what you want.

更新2

一个AsyncTask：

Ok here is your code using an AsyncTask:

public class Activity1 extends Activity
{
    private ProgressDialog progressDialog;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        new AsyncTask<Integer, Integer, Boolean>()
        {
            ProgressDialog progressDialog;

            @Override
            protected void onPreExecute()
            {
                /*
                 * This is executed on UI thread before doInBackground(). It is
                 * the perfect place to show the progress dialog.
                 */
                progressDialog = ProgressDialog.show(Activity1.this, "",
                        "Loading...");
            }

            @Override
            protected Boolean doInBackground(Integer... params)
            {
                if (params == null)
                {
                    return false;
                }
                try
                {
                    /*
                     * This is run on a background thread, so we can sleep here
                     * or do whatever we want without blocking UI thread. A more
                     * advanced use would download chunks of fixed size and call
                     * publishProgress();
                     */
                    Thread.sleep(params[0]);
                    // HERE I'VE PUT ALL THE FUNCTIONS THAT WORK FOR ME
                }
                catch (Exception e)
                {
                    Log.e("tag", e.getMessage());
                    /*
                     * The task failed
                     */
                    return false;
                }

                /*
                 * The task succeeded
                 */
                return true;
            }

            @Override
            protected void onPostExecute(Boolean result)
            {
                progressDialog.dismiss();
                /*
                 * Update here your view objects with content from download. It
                 * is save to dismiss dialogs, update views, etc., since we are
                 * working on UI thread.
                 */
                AlertDialog.Builder b = new AlertDialog.Builder(Activity1.this);
                b.setTitle(android.R.string.dialog_alert_title);
                if (result)
                {
                    b.setMessage("Download succeeded");
                }
                else
                {
                    b.setMessage("Download failed");
                }
                b.setPositiveButton(getString(android.R.string.ok),
                        new DialogInterface.OnClickListener()
                        {

                            @Override
                            public void onClick(DialogInterface dlg, int arg1)
                            {
                                dlg.dismiss();
                            }
                        });
                b.create().show();
            }
        }.execute(2000);

        new Thread()
        {
            @Override
            public void run()
            {

                // dismiss the progressdialog
                progressDialog.dismiss();
            }
        }.start();
    }
}

这篇关于Android进度对话框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！