如何在数据加载到主活动布局时启动向用户显示UI屏幕的活动

Question

我想从数据库中加载主活动布局中的一些数据，而发生这种情况我想向用户显示一个数据弹出对话框。我尝试过使用线程和异步任务，但仍然屏幕冻结，而数据正在加载，最后当它完成时，它显示我的弹出窗口。我想让对话框同时显示数据加载。下面的 是加载数据并调用异步任务的主要活动的功能。

public void call_itemdisplay(final String bookid) 
    { 
     new waitAsync().execute(); 
     //load data from DB below 
     } 

启动一个新的活动

public class waitAsync extends AsyncTask<Void, Void, Void> { 
    @Override 
    protected Void doInBackground(Void... params) { 
    try { 
     Intent i = new Intent(MainActivity.mCon, waitActivity.class); 
     MainActivity.mCon.startActivity(i); 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
     return null; 
     } 


} 

由异步任务

public class waitActivity extends Activity { 
    static waitActivity wact; 
    public static Context wcon; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     wact=this; 

     setContentView(R.layout.activity_wait); 
    } 

} 

中显示的UI，同时弹出的活动需要帮助启动弹出式窗口活动的异步任务数据加载在主要活动中。目前，该屏幕冻结在加载数据，然后显示所有在一起后加载完成

有新的变化编辑：异步任务

public class waitAsync extends AsyncTask<String, Void, String> { 
    ResultSet rs=null; 
    private ProgressDialog processingDialog; 
    static Connection conn=null; 
    Statement stmt; 
    // waitThread wt= new waitThread(); 
    @Override 
    protected void onPreExecute() { 
     // ProgressDialog processingDialog; 
     super.onPreExecute(); 
     processingDialog = new ProgressDialog(MainActivity.mCon); 
     processingDialog.show(); 
     processingDialog.setContentView(R.layout.activity_wait); 
     //processingDialog.setMessage("Loading..."); 

    } 
    @Override 
    protected String doInBackground(String... params) { 
     try { 


      String driver = "net.sourceforge.jtds.jdbc.Driver"; 
      String ip = "mfb.dfsdfsdf.ap-north-1.rds.amazonaws.com"; 
      String classs = "net.sourceforge.jtds.jdbc.Driver"; 
      String db = "MyDatabase"; 
      String un = "xxxwww"; 
      String password = "xxxxxx"; 
      Class.forName(classs); 

      String ConnURL = null; 
      ConnURL = "jdbc:jtds:sqlserver://" + ip + ";" 
        + "databaseName=" + db + ";user=" + un + ";password=" 
        + password + ";"; 
      conn = DriverManager.getConnection(ConnURL); 

      stmt = conn.createStatement(
        ResultSet.TYPE_SCROLL_INSENSITIVE, 
        ResultSet.CONCUR_READ_ONLY); 
      rs=stmt.executeQuery(params[0]); 
      int size = 0; 


      //conn.close(); 
      MainActivity.getdata=rs; 
      MainActivity.flag=1; 
      //Thread.sleep(5000); 
     } catch (Exception e) 
     { 
      Log.w("Error connection", "" + e.getMessage()); 
     } 
     return null; 
     } 
    @Override 
    protected void onPostExecute(String s) { 
     super.onPostExecute(s); 
     processingDialog.dismiss(); 
     // wt.interrupted(); 


    } 



} 

异步任务从Main_Activity

呼叫

Getdata(String bookid) 
{ 
    String SQL="Select eb.book_name,eb.AuthorID,ma.Name,eb.GenreID_M,eb.GenreID_D,gm.Genre_MN+'- '+gd.Genre_DN as Genre,isnull(eb.pubDate,'') pubDate,isnull(eb.book_Loc,'') book_Loc,\n" + 
        " eb.Price,eb.ico_Loc,eb.Descrip from Master_ebook eb inner join Master_Author ma on eb.AuthorID=ma.Author_ID\n" + 
        " inner join Master_Genre_M gm on eb.GenreID_M=gm.Genre_MID\n" + 
        "inner join Master_Genre_D gd on eb.GenreID_D= gd.Genre_DID where eb.bookID=" + bookid; 


      new waitAsync().execute(SQL); 

      int c=0; 
      while(MainActivity.flag==0) 
      { 
       c++; 
      } 

      if(MainActivity.flag==1) 
      { 
       MainActivity.flag=0; 
       //processingDialog.dismiss(); 
      } 

      ResultSet rs=MainActivity.getdata; 
} 

Answer 1

在您的AsyncTask,

• 使用onPreExecute来显示01在个
• 加载数据，这种方法将在worker thread

• 隐藏对话框堪称onPostExecute

  ... AsyncTask<String, String, String>() { 
       @Override 
       protected void onPreExecute() { 
        super.onPreExecute(); 
        // show dialog 
       } 
      // UPDATE 
      @Override 
      protected void onProgressUpdate(String... values) { 
       super.onProgressUpdate(values); 
       // this method will be called when you call 
       // publishProgress from doInBackground. 
      }  
       @Override 
       protected String doInBackground(String[] params) { 
        // load data and return 
        // this data will passed to onPostExecute 
        publishProgress(param); // call onProgressUpdate 
        return null; 
       } 
  
       @Override 
       protected void onPostExecute(String o) { 
        super.onPostExecute(o); 
        // hide dialog 
       } 
  } 
  

这里有几个链接，你可以找到在实现自己的目标

有用

• AsyncTask Android example
• UI vs Worker Thread
• Showing progress dialog

Answer 2

可以显示你的对话是这样的。 onPreExecute（）方法将调用第一个在此方法中显示对话框。 然后doInBackground和doInBackground（）方法中的后台任务完成后，它会将其结果传递给onPostExecute（），您可以在这里放弃加载对话框。

class BackgroundTask extends AsyncTask<Void, Void, String> 
{ 
    ProgressDialog progressDialog; 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 

     progressDialog = new ProgressDialog(mContext); 
     progressDialog.setMessage("Loading..."); 
     progressDialog.show(); 
    } 

    @Override 
    protected String doInBackground(Void... params) { 

     //do your task here; 

     return null; 
    } 

    @Override 
    protected void onPostExecute(String s) { 
     super.onPostExecute(s); 
     progressDialog.dismiss(); 
    } 
} 

Answer 3

你必须首先使用onPreExecute（）方法，以显示对话框，然后在doInBackground从DATABSE获取您的数据（）方法，在下面的代码片段我已经showned你如何返回从获取的数据DB到onPostExecute（）方法，您可以进一步处理，最后您只需要关闭（）onPostExecute（）中的对话框并启动下一个活动。

private class waitAsync extends AsyncTask<Void, Void, String[]> { 
     private ProgressDialog processingDialog; 
     Context cnt = null; 
      waitAsync(Context cnt) 
      { 
       this.cnt = cnt; 
       } 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      // Showing progress dialog 
      processingDialog = new ProgressDialog(cnt); 
      processingDialog.setMessage("Loading..."); 
      processingDialog.show(); 
     } 

     @Override 
     protected String[] doInBackground(Void... arg0) { 
      //load data from DB below 
      return null; 
     } 

     @Override 
     protected void onPostExecute(String[] result) { 
      super.onPostExecute(result); 
      // Dismiss the progress dialog 
      processingDialog.dismiss(); 
      try { 
      Intent i = new Intent(cnt, waitActivity.class); 
      cnt.startActivity(i); 

      } catch (Exception e) { 
      e.printStackTrace(); 
      } 
     } 

    } 

您可以通过简单地调用ASYC任务调用此方法，这将在后台进行的话，这应该工作：

// Calling async task to fetch data from DB 
    new waitAsync (context).execute();