如何使用Async任务分页

Question

public class AndroidXMLParsingActivity extends Activity { 

    public int currentPage = 1; 
    public ListView lisView1; 
    static final String KEY_ITEM = "docdetails"; 
    static final String KEY_NAME = "heading"; 
    public Button btnNext; 
    public Button btnPre; 
    public static String url = "http://dev.taxmann.com/TaxmannService/TaxmannService.asmx/GetNotificationList?YearID=&CircularNo=33&SearchText=tax&pagenumber=1"; 

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

     // listView1 
     lisView1 = (ListView) findViewById(R.id.listView1); 

     // Next 
     btnNext = (Button) findViewById(R.id.btnNext); 
     // Perform action on click 
     btnNext.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
       currentPage = currentPage + 1; 
       ShowData(); 
      } 
     }); 

     // Previous 
     btnPre = (Button) findViewById(R.id.btnPre); 
     // Perform action on click 
     btnPre.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
       currentPage = currentPage - 1; 
       ShowData(); 
      } 
     }); 



     ShowData(); 
    } 

    public void ShowData() { 
     XMLParser parser = new XMLParser(); 
     String xml = parser.getXmlFromUrl(url); // getting XML 

     Document doc = parser.getDomElement(xml); // getting DOM element 

     NodeList nl = doc.getElementsByTagName(KEY_ITEM); 

     int displayPerPage = 5; // Per Page 
     int TotalRows = nl.getLength(); 
     int indexRowStart = ((displayPerPage * currentPage) - displayPerPage); 
     int TotalPage = 0; 
     if (TotalRows <= displayPerPage) { 
      TotalPage = 1; 
     } else if ((TotalRows % displayPerPage) == 0) { 
      TotalPage = (TotalRows/displayPerPage); 
     } else { 
      TotalPage = (TotalRows/displayPerPage) + 1; // 7 
      TotalPage = (int) TotalPage; // 7 
     } 
     int indexRowEnd = displayPerPage * currentPage; // 5 
     if (indexRowEnd > TotalRows) { 
      indexRowEnd = TotalRows; 
     } 

     // Disabled Button Next 
     if (currentPage >= TotalPage) { 
      btnNext.setEnabled(false); 
     } else { 
      btnNext.setEnabled(true); 
     } 

     // Disabled Button Previos 
     if (currentPage <= 1) { 
      btnPre.setEnabled(false); 
     } else { 
      btnPre.setEnabled(true); 
     } 

     // Load Data from Index 
     int RowID = 1; 
     ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>(); 
     HashMap<String, String> map; 

     // RowID 
     if (currentPage > 1) { 
      RowID = (displayPerPage * (currentPage - 1)) + 1; 
     } 

     for (int i = indexRowStart; i < indexRowEnd; i++) { 
      Element e = (Element) nl.item(i); 
      // adding each child node to HashMap key => value 
      map = new HashMap<String, String>(); 
      map.put("RowID", String.valueOf(RowID)); 
      map.put(KEY_NAME, parser.getValue(e, KEY_NAME)); 

      // adding HashList to ArrayList 
      menuItems.add(map); 

      RowID = RowID + 1; 

     } 

     SimpleAdapter sAdap; 
     sAdap = new SimpleAdapter(AndroidXMLParsingActivity.this, menuItems, 
       R.layout.list_item, new String[] { "RowID", KEY_NAME }, 
       new int[] { R.id.ColRowID, R.id.ColName }); 
     lisView1.setAdapter(sAdap); 
    } 

} 

这是我的源代码我想使用Async任务来解析数据，但即时通讯无法编写代码，该代码是能够在模拟器上打印数据，但是当我运行它时设备然后它意外关闭我想设置解析功能在背景

Answer 1

调整您的原始代码使用AsyncTask很容易实现。以下将工作

public class AndroidXMLParsingActivity extends Activity { 

    public int currentPage = 1; 
    ... 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     ... 
     btnNext.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
       currentPage = currentPage + 1; 
       //we pass in the page number every time so it knows what fetch 
       new AsyncPaginator().execute(currentPage); 
      } 
     }); 
     ... 
     btnPre.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
       currentPage = currentPage - 1; 
       new AsyncPaginator().execute(currentPage); 
      } 
     }); 
     new AsyncPaginator().execute(currentPage); 
    } 

    private class AsyncPaginator extends AsyncTask<Integer, Void, ArrayList<HashMap<String, String>>> { 

     int TotalPage = 0; 

     @Override 
     protected ArrayList<HashMap<String, String>> doInBackground(Integer... params) { 
      //the busy work happens here on another thread 
      XMLParser parser = new XMLParser(); 
      String xml = parser.getXmlFromUrl(url); // getting XML 
      Document doc = parser.getDomElement(xml); // getting DOM element 
      NodeList nl = doc.getElementsByTagName(KEY_ITEM); 
      int displayPerPage = 5; // Per Page 
      int TotalRows = nl.getLength(); 
      int indexRowStart = ((displayPerPage * currentPage) - displayPerPage); 
      if (TotalRows <= displayPerPage) { 
       TotalPage = 1; 
      } else if ((TotalRows % displayPerPage) == 0) { 
       TotalPage = (TotalRows/displayPerPage); 
      } else { 
       TotalPage = (TotalRows/displayPerPage) + 1; // 7 
      } 
      int indexRowEnd = displayPerPage * currentPage; // 5 
      if (indexRowEnd > TotalRows) { 
       indexRowEnd = TotalRows; 
      } 
      int RowID = 1; 
      ArrayList<HashMap<String, String>> menuItems = new ArrayList<>(); 
      HashMap<String, String> map; 
      if (currentPage > 1) { 
       RowID = (displayPerPage * (currentPage - 1)) + 1; 
      } 
      for (int i = indexRowStart; i < indexRowEnd; i++) { 
       Element e = (Element) nl.item(i); 
       map = new HashMap<>(); 
       map.put("RowID", String.valueOf(RowID)); 
       map.put(KEY_NAME, parser.getValue(e, KEY_NAME)); 
       menuItems.add(map); 
       RowID = RowID + 1; 
      } 
      return menuItems; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<HashMap<String, String>> menuItems) { 
      //when everything finishes we display the updates from here 
      super.onPostExecute(menuItems); 
      if (currentPage >= TotalPage) { 
       btnNext.setEnabled(false); 
      } else { 
       btnNext.setEnabled(true); 
      } 
      if (currentPage <= 1) { 
       btnPre.setEnabled(false); 
      } else { 
       btnPre.setEnabled(true); 
      } 
      lisView1.setAdapter(new SimpleAdapter(AndroidXMLParsingActivity.this, menuItems, 
       R.layout.list_item, new String[]{"RowID", KEY_NAME}, 
       new int[]{R.id.ColRowID, R.id.ColName})); 
     } 
    } 
}