安卓。 SQLite 异常 : no such column _id

Question

我在尝试获取存储在我的数据库中的信息并将其显示在 ListView 中时遇到了一些麻烦。

这是我要显示行的 ListActivity:

public class Prueba extends ListActivity{

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.i_prueba);

        DataBaseAccess db = new DataBaseAccess(this);
        db.open();

        Cursor result = db.getAllContact();
        startManagingCursor(result);


        // the desired columns to be bound
        String[] columns = new String[] {"_id", "nombre", "telefono", "mail"};
        // the XML defined views which the data will be bound to
        int[] to = new int[] { R.id.textid, R.id.textNombre, R.id.textTelefono, R.id.textMail };

        SimpleCursorAdapter mAdapter = new SimpleCursorAdapter(this, R.layout.i_listadb, result, columns, to);


        this.setListAdapter(mAdapter);

    }

数据库类。这是我收到错误的 getAllContact 方法:

公共(public)类数据库访问{

public static final String NOMBRE = "nombre";
public static final String TELEFONO = "telefono";
public static final String MAIL = "mail";
public static final String ID = "_id";


    public DataBaseAccess(Context context) {
        this.androidContext = context;
//DataBaseHelper is another class where the Database is created. In the "onCreate" //method of that class is where i make the CREATE TABLE and add some values to that //table.
        dbHelper = new DataBaseHelper(androidContext);  
    }



    public void open() throws SQLException {
        db = dbHelper.getWritableDatabase();
        }



[...MORE METHODS...]

    public Cursor getAllContact(){
        String[] columnas = new String[] {ID, NOMBRE, TELEFONO, MAIL};
        Cursor mCursor = dbHelper.query("t_contactos", columnas, null, null, null, null, null);
    if (mCursor != null){
        mCursor.moveToFirst();
    }
    return mCursor;
}

这是来自 LogCat 的错误消息:

E/AndroidRuntime(  636): Uncaught handler: thread main exiting due to uncaught exception

E/AndroidRuntime(  636): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.pfc.android/com.pfc.android.Prueba}: android.database.sqlite.SQLiteException: no such column: _id: , while compiling: SELECT _id, nombre, telefono, mail FROM t_contactos

E/AndroidRuntime(  636):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401)

E/AndroidRuntime(  636):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)

E/AndroidRuntime(  636):    at android.app.ActivityThread.access$2100(ActivityThread.java:116)

E/AndroidRuntime(  636):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)

E/AndroidRuntime(  636):    at android.os.Handler.dispatchMessage(Handler.java:99)

E/AndroidRuntime(  636):    at android.os.Looper.loop(Looper.java:123)

E/AndroidRuntime(  636):    at android.app.ActivityThread.main(ActivityThread.java:4203)

E/AndroidRuntime(  636):    at java.lang.reflect.Method.invokeNative(Native Method)

E/AndroidRuntime(  636):    at java.lang.reflect.Method.invoke(Method.java:521)

E/AndroidRuntime(  636):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)

E/AndroidRuntime(  636):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)

E/AndroidRuntime(  636):    at dalvik.system.NativeStart.main(Native Method)

E/AndroidRuntime(  636): Caused by: android.database.sqlite.SQLiteException: no such column: _id: , while compiling: SELECT _id, nombre, telefono, mail FROM t_contactos

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteProgram.native_compile(Native Method)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteProgram.compile(SQLiteProgram.java:110)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:59)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1118)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1006)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:964)

E/AndroidRuntime(  636):    at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1041)

E/AndroidRuntime(  636):    at com.pfc.android.DataBaseAccess.getAllContact(DataBaseAccess.java:97)

E/AndroidRuntime(  636):    at com.pfc.android.Prueba.onCreate(Prueba.java:21)

E/AndroidRuntime(  636):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)

E/AndroidRuntime(  636):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)

E/AndroidRuntime(  636):    ... 11 more

那么，有人可以帮助解决这个问题吗？ 提前谢谢你!

Answer 1

例如，如果您使用字段“a”、“b”和“c”创建了数据库并使用了此数据库，那么如果您添加新字段(例如“d”)，您需要在手机上重新创建数据库(只需删除它)。