無法啓動活動ComponentInfo

我正在創建一個可以搜索表'employee'並返回結果的應用程序。我正在使用searchdialog進行搜索。但是我按下了搜索對話框上的搜索按鈕。請幫助我。無法啓動活動ComponentInfo

代碼：

public class SimpleSearch extends ListActivity { 
    protected SQLiteDatabase db; 
    protected Cursor cursor; 
    protected ListAdapter adapter; 
    protected String query; 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     Intent intent = getIntent(); 
     if (Intent.ACTION_SEARCH.equals(intent.getAction())) { 
      String query = intent.getStringExtra(SearchManager.QUERY); 
      doMySearch(query); 
      } 
     } 

    private void doMySearch(String query) { 
     cursor = db.rawQuery("SELECT _id, firstName, lastName, title FROM employee WHERE firstName || ' ' || lastName LIKE ?", 
        new String[]{"%" + query + "%"}); 
     adapter = new SimpleCursorAdapter(
       this, 
       R.layout.emp_list_item, 
       cursor, 
       new String[] {"firstName", "lastName", "title"}, 
       new int[] {R.id.firstName, R.id.lastName, R.id.title}); 
     setListAdapter(adapter); 

    } 

}

錯誤，堆棧跟蹤：

shortMsg:java.lang.NullPointerException 
longMsg:java.lang.NullPointerException: Unable to start activity ComponentInfo{com.simple.search/com.simple.search.SimpleSearch}: java.lang.NullPointerException 
stackTrace:java.lang.RuntimeException: Unable to start activity ComponentInfo{com.simple.search/com.simple.search.SimpleSearch}: java.lang.NullPointerException 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1664) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1680) 
at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:130) 
at android.app.ActivityThread.main(ActivityThread.java:3703) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:507) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException 
at com.simple.search.SimpleSearch.onCreate(SimpleSearch.java:34) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1628) 
... 11 more

Databasehelper

public class DatabaseHelper extends SQLiteOpenHelper { 

    public static final String DATABASE_NAME = "test_diectory"; 

    protected Context context; 

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

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     String s; 
     try { 
      Toast.makeText(context, "1", 2000).show(); 
      InputStream in = context.getResources().openRawResource(R.raw.sql); 
      DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); 
      Document doc = builder.parse(in, null); 
      NodeList statements = doc.getElementsByTagName("statement"); 
      for (int i=0; i<statements.getLength(); i++) { 
       s = statements.item(i).getChildNodes().item(0).getNodeValue(); 
       db.execSQL(s); 
      } 
     } catch (Throwable t) { 
      Toast.makeText(context, t.toString(), 50000).show(); 
     } 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     db.execSQL("DROP TABLE IF EXISTS employees"); 
     onCreate(db); 
    } 

}

來源

2011-11-29 Binoy Babu

什麼是你的光標getCount（）？調試它.. – user370305

什麼是行34. –

你能解釋一下怎麼做嗎？我是新的eclipse和android。 –

感謝阿迪爾。看起來我忘了初始化分貝。添加db = (new DatabaseHelper(this)).getWritableDatabase();修復了錯誤。

來源

2011-11-29 23:20:59

無法啓動活動ComponentInfo

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