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如何在列表視圖中顯示emptyview以防萬一我的適配器爲空？

2012-10-16 15 views
0

我想在我的列表視圖中顯示一個按鈕，以防萬一我沒有數據通過自定義數組適配器填充列表。如果我有數據和我的列表視圖獲取數據項填充，但如果我沒有數據項目顯示列表視圖應該顯示LinearLayout ID爲「@android：ID /空」，但它從來沒有顯示這個和我的應用程序在這個階段崩潰。在我的FavoriteStudents.java類文件我有一個AsyncTask defined.In。 doInBackground方法我檢查我的手機內部存儲器中是否存在最喜歡的文件以創建用於listview的適配器，如果沒有，則停止AsyncTask並顯示帶有buttom的列表視圖。從doInBackground方法返回後，它崩潰並向我顯示此錯誤：如何在列表視圖中顯示emptyview以防萬一我的適配器爲空？

10-16 16:06:37.568: E/WindowManager(274): Activity com.example.hellogridview.FavoriteStudets has leaked window [email protected] that was originally added here 
10-16 16:06:37.568: E/WindowManager(274): android.view.WindowLeaked: Activity com.example.hellogridview.FavoriteStudents has leaked window [email protected] that was originally added here 
10-16 16:06:37.568: E/WindowManager(274): at android.view.ViewRoot.<init>(ViewRoot.java:227) 
10-16 16:06:37.568: E/WindowManager(274): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148) 
10-16 16:06:37.568: E/WindowManager(274): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91) 
10-16 16:06:37.568: E/WindowManager(274): at android.view.Window$LocalWindowManager.addView(Window.java:424) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.Dialog.show(Dialog.java:239) 
10-16 16:06:37.568: E/WindowManager(274): at com.example.hellogridview.FavoriteStudents$readingFavFileTask.onPreExecute(FavoriteStudents.java:50) 
10-16 16:06:37.568: E/WindowManager(274): at android.os.AsyncTask.execute(AsyncTask.java:391) 
10-16 16:06:37.568: E/WindowManager(274): at com.example.hellogridview.FavoriteStudents.onCreate(FavoriteStudents.java:34) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.ActivityThread.access$2200(ActivityThread.java:119) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863) 
10-16 16:06:37.568: E/WindowManager(274): at android.os.Handler.dispatchMessage(Handler.java:99) 
10-16 16:06:37.568: E/WindowManager(274): at android.os.Looper.loop(Looper.java:123) 
10-16 16:06:37.568: E/WindowManager(274): at android.app.ActivityThread.main(ActivityThread.java:4363) 
10-16 16:06:37.568: E/WindowManager(274): at java.lang.reflect.Method.invokeNative(Native Method) 
10-16 16:06:37.568: E/WindowManager(274): at java.lang.reflect.Method.invoke(Method.java:521) 
10-16 16:06:37.568: E/WindowManager(274): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 
10-16 16:06:37.568: E/WindowManager(274): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 
10-16 16:06:37.568: E/WindowManager(274): at dalvik.system.NativeStart.main(Native Method)

我的XML文件

<?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:orientation="vertical" > 

    <ListView 
     android:id="@+id/studentsList" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:divider="#b5b5b5" 
     android:dividerHeight="1dp" 
     android:listSelector="@drawable/student_list_selector" > 
    </ListView> 

    <!-- empty view --> 

    <LinearLayout 
     android:id="@android:id/empty" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" > 

     <Button 
      android:id="@+id/addStudents" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="Add Students" > 
     </Button> 
    </LinearLayout> 

</LinearLayout>

我的學生適配器

public class StudentsAdapter extends ArrayAdapter<Students> { 

    private Context context; 
    ImageDownloaderNew imageDownloader; 
    ArrayList<Students> students; 
    Songs studentsTemp = null; 
    int targetWidth = 70; 
    int targetHeight = 110; 

    public StudentsAdapter (Context context, int textViewResourceId, 
      ArrayList<Students> students) { 
     super(context, textViewResourceId, songs); 
     // TODO Auto-generated constructor stub 
     this.context = context; 
     this.students= students; 
     imageDownloader = new ImageDownloaderNew(); 
    } 

    @Override 
    public int getCount() { 
     // TODO Auto-generated method stub 

     return students.size(); 
    } 

    @Override 
    public Students getItem(int position) { 
     // TODO Auto-generated method stub 
     return null; 
    } 

    @Override 
    public long getItemId(int position) { 
     // TODO Auto-generated method stub 
     return 0; 
    } 

    static class ViewHolder { 
     protected TextView studentTitle; 
     protected RatingBar studentRating; 
     protected TextView studentViews; 
     protected ImageView studentImage; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // TODO Auto-generated method stub 

     //My getView code goes here.I have not pasted here 
     return convertView; 

    } 

}

現在FavoriteStudents.java類文件

public class FavoriteStudents extends SherlockActivity { 

    ListView list; 
    StudentsAdapter adapter; 
    ArrayList<Students> studentsListArray = new ArrayList<Students>(); 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 

     setContentView(R.layout.students_list); 

     new readingFavFileTask().execute(UtilityFuctions.FAV_STUDENTS_FILE_NAME); 
    } 

    private class readingFavFileTask extends AsyncTask<String, Void, String> { 

     ProgressDialog m_dialog = new ProgressDialog(FavoriteStudents.this); 

     @Override 
     protected void onPreExecute() { 
      // TODO Auto-generated method stub 
      super.onPreExecute(); 
      // initialize the dialog 
      m_dialog.setTitle("Loading..."); 
      m_dialog.setMessage("Please wait while loading..."); 
      m_dialog.setIndeterminate(true); 
      m_dialog.setCancelable(true); 
      m_dialog.show(); 

     } 

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

      if (!UtilityFuctions.isFileExists(getApplicationContext(), 
        params[0])) { 
       // favorite file does not exists 
       finish(); 
       return "fileDoesNotExists"; 
      }else{ 
      StudentsListArray = UtilityFuctions.readFavJSONFile(
        getApplicationContext(), params[0]); 
      if (isCancelled()) 
       finish(); 
      return null;} 
     } 

     @Override 
     protected void onPostExecute(String result) { 
      list = (ListView) findViewById(R.id.studentsList); 
      if (result.equals("fileDoesNotExists")) { 
       adapter = new StudentsAdapter(FavoriteStudents.this, 1, 
         studentsListArray); 
       list.setAdapter(adapter); 
          LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE); 
      View myView = inflater.inflate(R.layout.empty_view, null); 
          list.setEmptyView(myView); 
          m_dialog.dismiss(); 

      } else { 
       // Creating a StudentsAdapter and setting it on listview 

       adapter = new StudentsAdapter(FavoriteStudents.this, 1, 
         studentsListArray); 
       list.setAdapter(adapter); 
       m_dialog.dismiss(); 

       // Click event for single list row 
       list.setOnItemClickListener(new OnItemClickListener() { 

        @Override 
        public void onItemClick(AdapterView<?> parent, View view, 
          int position, long id) { 
             //onItemClick code goes here 

        } 
       }); 
      } 
     } 
    } 

}

編輯：@Rol f Smith的答案是正確的。但主要問題是我在我的doInBackground（）方法中調用了finish（），它正在殺死我的活動，並沒有向我顯示emptyView。因此，我只是刪除了finish（）和一切正常工作。 Thanks EveryOne

來源

2012-10-16 Anshul

+1

修改您的適配器的getView，以便在沒有數據的情況下使用按鈕返回線性佈局？或者使用ListView.setEmptyView（） – Shark

+0

好的我正在嘗試ListView.setEmptyView（） – Anshul

+0

感謝@Shark的幫助 – Anshul

回答

6

空視圖（使用android空id）僅在使用ListActivity或ListFragment時有效，在這種情況下，您必須使用setEmptyView()方法執行自己的邏輯。

ListView.setEmptyView()

和你有崩潰可能是因爲當你的活動關閉已顯示的對話框沒有被駁回。因此，例如在onPause方法中，從您顯示的對話框中調用dismiss方法。

羅爾夫

編輯看評論：

空的觀點將與View.GONE顯示和View.VISIBLE這意味着你不需要添加它你的自我等

看看這段代碼： 並仔細看看onCreate方法。

import android.widget.ListView; 

public class FavoriteStudents extends SherlockActivity { 

    ListView list; 
    StudentsAdapter adapter; 
    ArrayList<Students> studentsListArray = new ArrayList<Students>(); 
    private ListView list; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 

     setContentView(R.layout.students_list); 
     list = (ListView) findViewById(R.id.studentsList); 

     View empty = findViewById(R.id.empty_view); 
     list.setEmptyView(empty); 

     new readingFavFileTask().execute(UtilityFuctions.FAV_STUDENTS_FILE_NAME); 
    } 

    private class readingFavFileTask extends AsyncTask<String, Void, String> { 

     ProgressDialog m_dialog = new ProgressDialog(FavoriteStudents.this); 

     @Override 
     protected void onPreExecute() { 
      // TODO Auto-generated method stub 
      super.onPreExecute(); 
      // initialize the dialog 
      m_dialog.setTitle("Loading..."); 
      m_dialog.setMessage("Please wait while loading..."); 
      m_dialog.setIndeterminate(true); 
      m_dialog.setCancelable(true); 
      m_dialog.show(); 

     } 

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

      if (!UtilityFuctions.isFileExists(getApplicationContext(), 
        params[0])) { 
       // favorite file does not exists 
       finish(); 
       return "fileDoesNotExists"; 
      }else{ 
      StudentsListArray = UtilityFuctions.readFavJSONFile(
        getApplicationContext(), params[0]); 
      if (isCancelled()) 
       finish(); 
      return null;} 
     } 

     @Override 
     protected void onPostExecute(String result) { 
      if (result.equals("fileDoesNotExists")) { 
       adapter = new StudentsAdapter(FavoriteStudents.this, 1, studentsListArray); 
       list.setAdapter(adapter); 
       m_dialog.dismiss(); 

      } else { 
       // Creating a StudentsAdapter and setting it on listview 

       adapter = new StudentsAdapter(FavoriteStudents.this, 1, 
         studentsListArray); 
       list.setAdapter(adapter); 
       m_dialog.dismiss(); 

       // Click event for single list row 
       list.setOnItemClickListener(new OnItemClickListener() { 

        @Override 
        public void onItemClick(AdapterView<?> parent, View view, 
          int position, long id) { 
             //onItemClick code goes here 

        } 
       }); 
      } 
     } 
    } 

}

來源

2012-10-16 10:48:24

+0

好吧，讓我在一分鐘內回覆您。希望它的作品。:) – Anshul

+0

編輯我的文章！ –

+0

找到這個鏈接，它可以幫助你： http://stackoverflow.com/questions/3771568/how-to-show-empty-view-when-listview-is-empty –

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