Android 进度对话框 [英] Android progress dialog

问题描述

我的应用程序从 Internet 获取一些 html 代码，完成后，将其显示在设备屏幕上.由于这样做大约需要 3-4 秒，因此此时屏幕保持黑色，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();

程序可以运行，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.

你能帮帮我吗?提前致谢.

Could you please help me ? Thanks in advance.

推荐答案

这个错误已经足够解释了.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是调用 runOnUiThread().

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().

但是，在您的情况下，我会使用 AsyncTask 下载并更新进度条的进度.该任务具有在结束时在 UI 线程上运行的属性(因此您可以在那里更新视图，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)

这里是如何使用 AsyncTask 显示下载进度对话框的示例.

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

更新

Stackoverflow 已经为您提供了所有问题的答案.这里 是一个 AsyncTask 示例，用于下载一些内容并显示下载进度.正是你想要的.

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

好的，这是您使用 AsyncTask 的代码:

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！