Question

我有xml的代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="15px"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Loading..."
/>
<ProgressBar android:id="@+id/progressBar"
android:paddingTop="10px"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:max="100" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/txt"
/>
</LinearLayout>

然后为班级：

public class Loading extends Activity {
     ProgressBar bar;
     TextView txt;
     int total=0;
     boolean isRunning=false;
     // handler for the background updating
     Handler handler=new Handler() {
         @Override
         public void handleMessage(Message msg) {
             total=total+5;
             String perc=String.valueOf(total).toString();
             txt.setText(perc+"% completed");
             bar.incrementProgressBy(5);
         }
     };

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.loading_bar);
        bar=(ProgressBar)findViewById(R.id.progressBar);
        txt=(TextView)findViewById(R.id.txt);
    }

    public void onStart() {
        super.onStart();
        // reset the bar to the default value of 0
        bar.setProgress(0);
          // create a thread for updating the progress bar
         Thread background=new Thread(new Runnable() {
             public void run() {
                 try {
                     for (int i=0;i<20 && isRunning;i++) {
                         // wait 1000ms between each update
                         Thread.sleep(1000);
                         handler.sendMessage(handler.obtainMessage());
                     }
                 }
                 catch (Throwable t) {  

                 }     
             }    
         });

         isRunning=true;
         // start the background thread
         background.start();
     }

    public void onStop() {
        super.onStop();
        isRunning=false;
     }
}

有了这个，我把它叫做另一个活动：

public void onClick (View v)
        {
            switch (v.getId())
            {
            case R.id.buttonNext3:
                Intent Loading = new Intent(this, Loading.class);
                startActivity(Loading);
                getContent();               
            Call();             
                db.generation();
                Intent Next3 = new Intent(this, FoodPlanning.class);
                startActivity(Next3);
                break;
            }

        }

但它不适用于我的，它只是显示黑屏，但它仍在进行中......我想在我点击按钮时出现加载栏并且过程仍在进行中。任何的想法？你好

Answer 1

正如Adil所建议的，AsyncTask是运行后台任务的首选方法，它具有在UI线程上运行某些命令的简单选项，同时将其余命令推送到后台。请参阅SDK中的此示例（http://developer.android.com/reference/android/os/AsyncTask.html）：

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
 protected Long doInBackground(URL... urls) {
     int count = urls.length;
     long totalSize = 0;
     for (int i = 0; i < count; i++) {
         totalSize += Downloader.downloadFile(urls[i]);
         publishProgress((int) ((i / (float) count) * 100));
     }
     return totalSize;
 }

 protected void onProgressUpdate(Integer... progress) {
     setProgressPercent(progress[0]);
 }

 protected void onPostExecute(Long result) {
     showDialog("Downloaded " + result + " bytes");
 }
}

请注意“onProgressUpdate”方法以及doInBackground。

我的ProgressBar没有出现在Android上

1 个答案: