Android - 填充ListActivity數據庫搜索 - HowTo？

我得到了一個ListActivity，它從數據庫中獲取數據。此活動也被允許在數據庫中搜索數據。Android - 填充ListActivity數據庫搜索 - HowTo？

DatabaseHelper dbHelper; 
SimpleCursorAdapter adapter; 
Cursor c; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    requestWindowFeature(Window.FEATURE_NO_TITLE); 

    final Intent queryIntent = getIntent(); 
    final String queryAction = queryIntent.getAction(); 
    if (Intent.ACTION_SEARCH.equals(queryAction)) { 
     String searchKeywords = queryIntent.getStringExtra(SearchManager.QUERY); 
     doSearch(searchKeywords); 
    } 
} 

@Override 
public void onStart() { 
    try { 
     super.onStart(); 
     dbHelper=new DatabaseHelper(this); 
     c = dbHelper.getAllMagazines(); 
     startManagingCursor(c); 

     adapter = new SimpleCursorAdapter(this, 
       android.R.layout.simple_list_item_2, c, 
       new String[] {"editionName", "magazineName"}, 
       new int[] {android.R.id.text1, android.R.id.text2}); 

     /** Adapter setzen**/ 
     this.setListAdapter(adapter); 
    } 
    catch(Exception ex) { 
    } 
}

它在ListView中顯示數據庫中的數據。所以這裏沒問題。當我做了搜索，下面的函數被調用：

private void doSearch(String search) {  
    dbHelper=new DatabaseHelper(this); 
    c = dbHelper.searchEditions(getIntent().getStringExtra("search")); 
    startManagingCursor(c); 

    adapter = new SimpleCursorAdapter(this, 
      android.R.layout.simple_list_item_2, c, 
      new String[] {"editionName", "magazineName"}, 
      new int[] {android.R.id.text1, android.R.id.text2}); 

    this.setListAdapter(adapter); 
}

我的ListAdapter設置爲與SearchResult所新的適配器。但是在搜索的ResultView中，它仍然顯示我在onStart（）中獲得的數據庫中的所有數據。如果我禁用了onStart（）中的setListAdapter，那麼一切正常，它向我顯示searchresulst。

如何在ListView已經填充數據時告訴ListView顯示搜索結果？

全碼：

public class MagazineViewController extends ListActivity { 

    DatabaseHelper dbHelper; 
    SimpleCursorAdapter adapter; 
    Cursor c; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     requestWindowFeature(Window.FEATURE_NO_TITLE); 

     final Intent queryIntent = getIntent(); 
     final String queryAction = queryIntent.getAction(); 
     if (Intent.ACTION_SEARCH.equals(queryAction)) { 
      String searchKeywords = queryIntent.getStringExtra(SearchManager.QUERY); 
      doSearch(searchKeywords); 
     } 
    } 

    @Override 
    public void onStart() { 
     try { 
      super.onStart(); 
      dbHelper=new DatabaseHelper(this); 

      c = dbHelper.getAllMagazines(); 
      startManagingCursor(c); 

      Log.d("CURSOR COUNT", ""+c.getCount()); 

      adapter = new SimpleCursorAdapter(this, 
        android.R.layout.simple_list_item_2, c, 
        new String[] {"editionName", "magazineName"}, 
        new int[] {android.R.id.text1, android.R.id.text2}); 

      this.setListAdapter(adapter); 
     } 
     catch(Exception ex) { 
     } 
    } 

    private void doSearch(String search) {  
     dbHelper=new DatabaseHelper(this); 

     /** Daten aus der Datenbank abfragen**/ 
     Cursor cur = dbHelper.searchEditions(getIntent().getStringExtra("search")); 
     startManagingCursor(cur); 

     Log.d("CURSOR COUNT", ""+cur.getCount()); 

     final ListView view = getListView(); 
     final SimpleCursorAdapter cursorAdapter = ((SimpleCursorAdapter) view.getAdapter()); 
     cursorAdapter.changeCursor(cur); 
    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     MenuInflater inflater = getMenuInflater(); 
     inflater.inflate(R.menu.magazinemenu, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     switch (item.getItemId()) { 
      case R.id.preferences: 
       startActivity (new Intent (this, PreferencesViewController.class)); 
       break; 
     } 
     return true; 
    } 
}

logcat的：在管線111

03-30 16:29:43.381: ERROR/AndroidRuntime(546): FATAL EXCEPTION: main 
03-30 16:29:43.381: ERROR/AndroidRuntime(546): java.lang.RuntimeException: Unable to start activity ComponentInfo{package/package.MagazineViewController}: java.lang.NullPointerException 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.os.Handler.dispatchMessage(Handler.java:99) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.os.Looper.loop(Looper.java:123) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at java.lang.reflect.Method.invoke(Method.java:521) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at dalvik.system.NativeStart.main(Native Method) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546): Caused by: java.lang.NullPointerException 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at package.MagazineViewController.doSearch(MagazineViewController.java:111) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at package.MagazineViewController.onCreate(MagazineViewController.java:40) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
03-30 16:29:43.381: ERROR/AndroidRuntime(546):  ... 11 more

錯誤代碼，這是cursorAdapter.changeCursor（CUR）;

來源

2011-03-30 liquid

嘗試調用SimpleCursorAdapter。 changeCursor，而不是創建新的適配器實例。

我不認爲你需要這些行：

final ListView view = getListView(); 
final SimpleCursorAdapter cursorAdapter = ((SimpleCursorAdapter) view.getAdapter());

恰克：

cursorAdapter.changeCursor(cur);

要：

adapter.changeCursor(cur);

來源

2011-03-30 13:18:08 elevine

如果我改變到adapter.changeCursor（C）;而不是創建一個新的適配器實例，我得到一個NullPointerException。但光標數> 0。 – liquid 2011-03-30 13:49:15

是否有異常告訴您適配器爲空？你能提供你的新代碼和完整的堆棧跟蹤嗎？你能向我們展示你活動中的所有代碼嗎？ – elevine 2011-03-30 14:17:04

我把它放在第一個線程 – liquid 2011-03-30 14:41:31

MagazineViewController.class：

public class MagazineViewController extends ListActivity { 

DatabaseHelper dbHelper; 
SimpleCursorAdapter adapter = null; 
Cursor c; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    requestWindowFeature(Window.FEATURE_NO_TITLE); 

    final Intent queryIntent = getIntent(); 
    final String queryAction = queryIntent.getAction(); 
    if (Intent.ACTION_SEARCH.equals(queryAction)) { 
     String searchKeywords = queryIntent.getStringExtra(SearchManager.QUERY); 
     doSearch(searchKeywords); 
    } 

    dbHelper=new DatabaseHelper(this); 
} 

@Override 
public void onStart() { 
    super.onStart(); 

    dbHelper=new DatabaseHelper(this); 

    c = dbHelper.getAllMagazines(); 
    startManagingCursor(c); 

    Log.d("CURSOR COUNT", ""+c.getCount()); 

    adapter = new SimpleCursorAdapter(this, 
       android.R.layout.simple_list_item_2, c, 
       new String[] {"editionName", "magazineName"}, 
       new int[] {android.R.id.text1, android.R.id.text2}); 


    this.setListAdapter(adapter); 
} 

private void doSearch(String search) {  
    dbHelper=new DatabaseHelper(this); 

    Cursor cur = dbHelper.searchEditions(search); 
    startManagingCursor(cur); 

    Log.d("CURSOR2 COUNT", ""+cur.getCount()); 

    adapter.changeCursor(cur); 
}

個

DatabaseHelper.class：

public class DatabaseHelper extends SQLiteOpenHelper { 

public static final String DATABASE_NAME = "magazineDB"; 
public static final String TABLE_MAGAZINE = "magazine"; 
public static final String TABLE_EDITION = "edition"; 
public static final String TABLE_ARTICLE = "article"; 
public static final String TABLE_KEYWORDS = "keywords"; 

public DatabaseHelper(Context context) { 
    super(context, DATABASE_NAME, null,1); 
} 


@Override 
public void onCreate(SQLiteDatabase db) { 

    db.execSQL("CREATE TABLE " + TABLE_MAGAZINE + " (magazineId INTEGER PRIMARY KEY, " + 
"magazineName TEXT);"); 

    /** Tabelle "Edition" erstellen **/ 
    db.execSQL("CREATE TABLE " + TABLE_EDITION + " (_id INTEGER PRIMARY KEY AUTOINCREMENT," + 
"editionId INTEGER, " + 
"editionName TEXT, " + 
"editionContent TEXT, " + 
"magazine_id INTEGER NOT NULL, " + 
"FOREIGN KEY (magazine_id) REFERENCES " + TABLE_MAGAZINE + "(magazineId));"); 

    db.execSQL("CREATE TRIGGER fki_edition_magazine_id " + 
      " BEFORE INSERT ON "+ TABLE_EDITION + 
      " FOR EACH ROW BEGIN"+ 
      " SELECT CASE WHEN ((SELECT magazineId FROM "+ TABLE_MAGAZINE +" WHERE magazineId = new.magazine_id) IS NULL)"+ 
      " THEN RAISE (ABORT,'Foreign Key Violation') END;"+ 
      " END;"); 

} 


@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_MAGAZINE); 
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_EDITION); 
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_ARTICLE); 

    db.execSQL("DROP TRIGGER IF EXISTS fki_edition_magazine_id"); 

    onCreate(db); 
} 

Cursor getAllMagazines() { 
    SQLiteDatabase db=this.getWritableDatabase(); 
    Cursor cur= db.rawQuery("SELECT * FROM edition, magazine WHERE edition.magazine_id = magazine.magazineId", null); 
    return cur; 
} 

public Cursor searchEditions (String searchtext) { 
    SQLiteDatabase db=this.getWritableDatabase(); 
    Cursor cur= db.rawQuery("SELECT * FROM edition, magazine WHERE edition.magazine_id = magazine.magazineId AND edition.editionContent LIKE '%" + searchtext + "%'" ,null); 

    return cur; 
}

來源

2011-03-30 17:59:15 liquid

最後我得到了解決方案！我必須在onCreate（）方法中的doSearch（）之前初始化ListAdapter。謝謝你的幫助！對此，我真的非常感激。 – liquid 2011-03-30 19:55:12

Android - 填充ListActivity數據庫搜索 - HowTo？

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