爲什麼ListView在每次向下滾動時都會重複數據

Question

即時通訊軟件Android版。從json獲取數據，每頁顯示6條新聞，當我向下滾動時，應該顯示下一條6條新聞。 http://sentienich.aviostore.com/api/cunghoangdao/danhsach_baiviet.php?theloai=4

這個網址： http://sentienich.aviostore.com/api/cunghoangdao/danhsach_baiviet.php?theloai=4&page=2

應該給我JSON數據的下一頁第2頁 上，並用我的ListView驚人。

MainActivity

public class PaginationDemoActivity extends Activity { 
    AmazingListView lsComposer; 
    PaginationComposerAdapter adapter; 
    ArrayList<Composer> list =new ArrayList<Composer>(); 
    ArrayList<Composer> list1 = new ArrayList<Composer>(); 
    private String url = "http://sentienich.aviostore.com/api/cunghoangdao/danhsach_baiviet.php?theloai=4"; 

    private static int pageCount = 1 ; 

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

     lsComposer = (AmazingListView) findViewById(R.id.lsComposer); 
     lsComposer.setLoadingView(getLayoutInflater().inflate(R.layout.loading_view, null)); 
     lsComposer.setAdapter(adapter = new PaginationComposerAdapter()); 

     try { 
      list = new docJSon().execute().get(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } catch (ExecutionException e) { 
      e.printStackTrace(); 
     } 
     adapter.notifyMayHaveMorePages(); 

    } 

    public void bRefresh_click(View v) { 
     adapter.reset(); 
     adapter.resetPage(); 
     adapter.notifyMayHaveMorePages(); 
    } 

    class PaginationComposerAdapter extends AmazingAdapter { 

     private AsyncTask<Integer, Void, Pair<Boolean, List<Composer>>> backgroundTask; 

     public void reset() { 
      if (backgroundTask != null) backgroundTask.cancel(false); 
      //list = Data.getRows(1).second; 
      notifyDataSetChanged(); 
     } 

     @Override 
     public int getCount() { 
      return list.size(); 
     } 

     @Override 
     public Composer getItem(int position) { 
      return list.get(position); 
     } 

     @Override 
     public long getItemId(int position) { 
      return position; 
     } 

     @Override 
     protected void onNextPageRequested(int page) { 
      Log.d(TAG, "Got onNextPageRequested page=" + page); 

      //tren nay la khi vuot xuong load them 
      if(pageCount < 1) 
       pageCount++; 
      runOnUiThread(new Runnable() { 
       @Override 
       public void run() { 
        try { 
         list1 = new docJSon().execute().get(); 
        } catch (InterruptedException e) { 
         e.printStackTrace(); 
        } catch (ExecutionException e) { 
         e.printStackTrace(); 
        } 
       } 
      }); 
      if (backgroundTask != null) { 
       backgroundTask.cancel(false); 
      } 

      backgroundTask = new AsyncTask<Integer, Void, Pair<Boolean, List<Composer>>>() { 
       @Override 
       protected Pair<Boolean, List<Composer>> doInBackground(Integer... params) { 
        int page = params[0]; 
        return Data.getRows(page); 
      } 

       @Override 
       protected void onPostExecute(Pair<Boolean, List<Composer>> result) { 
        if (isCancelled()) return; 
       // đoạn này là khi vuốt xuống nó add vào cái list đầu tiên 
        list.addAll(list1); 
        nextPage(); 
        notifyDataSetChanged(); 
        if (result.first) { 
         // still have more pages 
         notifyMayHaveMorePages(); 
        } else { 
         notifyNoMorePages(); 
        } 
       }; 
      }.execute(page); 
     } 

     @Override 
     protected void bindSectionHeader(View view, int position, boolean displaySectionHeader) {} 

     @Override 
     public View getAmazingView(int position, View convertView, ViewGroup parent) { 
      View res = convertView; 
      if (res == null) res = getLayoutInflater().inflate(R.layout.item_composer, null); 

      // we don't have headers, so hide it 
      res.findViewById(R.id.header).setVisibility(View.GONE); 

      TextView lName = (TextView) res.findViewById(R.id.lName); 
      TextView lYear = (TextView) res.findViewById(R.id.lYear); 

      Composer composer = getItem(position); 
      lName.setText(composer.name); 
      lYear.setText(composer.year); 

      return res; 
     } 

     @Override 
     public void configurePinnedHeader(View header, int position, int alpha) { 
     } 

     @Override 
     public int getPositionForSection(int section) { 
      return 0; 
     } 

     @Override 
     public int getSectionForPosition(int position) { 
      return 0; 
     } 

     @Override 
     public Object[] getSections() { 
      return null; 
     } 

    } 

    public class docJSon extends AsyncTask<String, Integer, ArrayList<Composer>> { 
     @Override 
     protected ArrayList<Composer> doInBackground(String... arg) { 
      url = "http://sentienich.aviostore.com/api/cunghoangdao/danhsach_baiviet.php?theloai=4&page=" +pageCount; 

      Parser jParser = new Parser(); 
      String json = jParser.getJSONData(url); 
      try{ 
       Composer b; 
       JSONArray mang = new JSONArray(json); 
       for (int i = 0; i < mang.length(); i++) { 
        b = new Composer(); 
        JSONObject cunghoangdao = mang.getJSONObject(i); 
        b.setName(cunghoangdao.getString("tieude")); 
        b.setYear(cunghoangdao.getString("id")); 
        list.add(b); 
       } 
      }catch(JSONException e){ 
       e.printStackTrace(); 
      } 
      return list; 

     } 
     protected void onPostExecute(ArrayList<Composer> s){ 
     } 
    } 
} 

分析器類

public class Parser { 
    static InputStream is = null; 
    static JSONObject jObj = null; 
    static String json = ""; 
    public String getJSONData(String url){ 
     try{ 
      DefaultHttpClient client = new DefaultHttpClient(); 
      HttpPost post = new HttpPost(url); 
      HttpResponse response = client.execute(post); 
      HttpEntity entity = response.getEntity(); 
      is = entity.getContent(); 
     }catch (UnsupportedEncodingException e) { 
      e.printStackTrace(); 
     } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     try { 
      BufferedReader reader = new BufferedReader(new InputStreamReader(
        is, "iso-8859-1"), 8); 
      StringBuilder sb = new StringBuilder(); 
      String line = null; 
      while ((line = reader.readLine()) != null) { 
       sb.append(line + "\n"); 
      } 
      is.close(); 
      json = sb.toString(); 
     } catch (Exception e) { 
      Log.e("Buffer Error", "Error converting result " + e.toString()); 
     } 

     return json; 
    } 
} 

activity_pagination_demo.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> 
<LinearLayout android:layout_height="wrap_content" android:id="@+id/linearLayout1" android:layout_width="fill_parent" android:background="#eee"> 
    <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Click the button to refresh to page 1" android:layout_weight="1"></TextView> 
    <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Refresh" android:onClick="bRefresh_click"></Button> 
</LinearLayout> 
<com.example.zkyun.amazinglistviewtest.AmazingListView android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/lsComposer" /> 

Answer 1

每次你的要求

url = "http://.../danhsach_baiviet.php?theloai=4&page=" + pageCount; 

與pageCount設置爲1。要使其工作，你需要使用的onNextPageRequested(int page)的page參數，並把它傳遞給docJSon莫名其妙。

此外，您最好將docJSon的實現與backgroundTask之一合併。目前您正在屏蔽UI線程

list1 = new docJSon().execute().get(); 

這樣做也可能解決您當前的問題。