下载我的文件时，setProgress 方法不会更新 ProgressBar

Question

1. 下载文件的代码：

   Dialog dialog;
   int totalSize = 0;
   ProgressBar mProgressBar;
   int downloadedSize = 0;
   
   public void downloadFile(){
       try {
           URL url = new URL("http://.../my_file.mp3");
           HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
   
           urlConnection.setRequestMethod("GET");
           urlConnection.setDoOutput(true);
   
           urlConnection.connect();
   
           File SDCardRoot = Environment.getExternalStorageDirectory();
   
           File dir = new File(SDCardRoot.getAbsolutePath(), "/dossier1/dossier2";
           dir.mkdirs();
   
           File file = new File(dir, "my_file.mp3");
   
           FileOutputStream fileOutput = new FileOutputStream(file);
   
           InputStream inputStream = urlConnection.getInputStream();
   
           totalSize = urlConnection.getContentLength();
   
           runOnUiThread(new Runnable() {
               public void run() {
                   mProgressBar.setMax(totalSize);
               }
           });
   
           byte[] buffer = new byte[1024];
           int bufferLength = 0;
   
           while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
               fileOutput.write(buffer, 0, bufferLength);
               downloadedSize += bufferLength;
   
               runOnUiThread(new Runnable() {
                   public void run() {
                       mProgressBar.setProgress(downloadedSize);
                   }
               });
           }
   
           fileOutput.close();
   
           runOnUiThread(new Runnable() {
               public void run() {
                   //mProgressBar.dismiss();
               }
           });
   
       } catch (final MalformedURLException e) {
           showError("Error : MalformedURLException " + e);
           e.printStackTrace();
       } catch (final IOException e) {
           showError("Error : IOException " + e);
           e.printStackTrace();
       }
       catch (final Exception e) {
           showError("Error : Please check your internet connection " + e);
       }
   }
   

2. showProgress 方法：

   public  void showProgress(){
   dialog = new Dialog(context);
   dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
   dialog.setContentView(R.layout.myprogressdialog);
   dialog.setTitle("Download Progress");
   
   TextView text = (TextView) dialog.findViewById(R.id.tv1);
   text.setText("Downloading...");
   cur_val = (TextView) dialog.findViewById(R.id.cur_pg_tv);
   cur_val.setText("Starting download...");
   dialog.show();
   
   mProgressBar = (ProgressBar)dialog.findViewById(R.id.progress_bar);
   mProgressBar.setProgress(0);
   mProgressBar.setProgressDrawable(context.getResources().getDrawable(R.drawable.blue_progress));
   }
   

3. mProgressDialog 的布局（res/layout 中的 myprogressdialog.xml）：

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:id="@+id/layout_root"
   android:orientation="vertical"
   android:padding="10dp">
   
   <TextView
   android:id="@+id/tv1"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:textColor="#FFF"
   android:text="hello"
   android:textStyle="bold"
   />
   
   <ProgressBar
   android:id="@+id/progress_bar"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:progress="0"
   android:layout_marginTop="5dp"
   android:layout_marginBottom="10dp"
   style="?android:attr/progressBarStyleHorizontal"
   android:maxHeight="10dip"
   android:minHeight="10dip"
   />
   
   <TextView
   android:id="@+id/cur_pg_tv"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:textColor="#0F0"
   android:text="hello"
   android:layout_marginTop="5dp"
   android:textStyle="bold|italic"    />
   
   </LinearLayout>
   

4. 用于为 mProgressBar 赋予蓝色的 XML（res/drawable 中的 blue_progress.xml）

   <?xml version="1.0" encoding="utf-8"?>
   <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
   
   <item android:id="@android:id/background">
   <shape>
       <corners android:radius="5dip" />
       <gradient android:startColor="#ff9d9e9d"
           android:centerColor="#ff5a5d5a"
           android:centerY="0.75"
           android:endColor="#ff747674"
           android:angle="270"
           />
   </shape>
   </item>
   <item android:id="@android:id/progress">
   <clip>
       <shape>
           <corners android:radius="5dip" />
           <gradient android:startColor="@android:color/holo_blue_bright"
               android:centerColor="@android:color/holo_blue_dark"
               android:centerY="0.75"
               android:endColor="@android:color/holo_blue_light"
               android:angle="270"
               />
       </shape>
   </clip>
   </item>
   </layer-list>
   

下载我的文件时，setProgress 方法不会更新 ProgressBar！ 你能建议我任何解决方案吗？

Answer 1

https://developer.android.com/reference/android/os/AsyncTask.html

我建议阅读 AsyncTask，因为其中有一些非常好的工具可以帮助您异步更新 UI 线程。
异步任务允许您在后台线程上运行任务，并在完成（或正在进行）时更新 UI。通常这允许您跳过制作 UI Runnables——但这取决于您的情况。

无论如何， 您要覆盖的方法是 AsyncTask 中的 onProgressUpdate。此外，它可能会为您在将来尝试完成此任务时省去一些麻烦。

祝你好运！希望有帮助。