Question

我在Android工作室有一个应用程序，我从外部数据库中获取一些数据。所以我想在某些情况下获取特定数据，我在我的databaseHelper中使用了一个if语句实际上对我不起作用。您可以在公共列表getListMbs（）中看到if语句。当我打开应用程序时，它实际上只是从表中获取所有内容，因此if不起作用。

public class DatabaseHelper extends SQLiteOpenHelper{
public static final String DBNAME = "mydb.sqlite";
public static final String DBLOCATION = "/data/data/com.hfad.myapp/databases/";
private Context mContext;
private SQLiteDatabase mDatabase;

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

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

public void openDatabase() {
    String dbPath = mContext.getDatabasePath(DBNAME).getPath();
    if(mDatabase != null && mDatabase.isOpen()) {
        return;
    }
    mDatabase = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READWRITE);
}

public void closeDatabase() {
    if(mDatabase!=null) {
        mDatabase.close();
    }
}

public List<Cases> getListCases() {
    Cases caze= null;
    List<Cases> casesList = new ArrayList<>();
    openDatabase();
    Cursor cursor = mDatabase.rawQuery("SELECT * FROM Cases", null);
    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
        caze = new Cases(cursor.getInt(0), cursor.getString(1), cursor.getString(2), cursor.getString(3), ListCases.pose);
        casesList.add(caze);
        cursor.moveToNext();
    }
    cursor.close();
    closeDatabase();
    return casesList;
}

public List<Motherboards> getListMbs() {
    Motherboards mbs = null;
    List<Motherboards> mbsList = new ArrayList<>();
    openDatabase();
    String query = ("SELECT * FROM Motherboards");
    if(ListCases.mboardsize == "mATX"){
        query="SELECT * FROM Motherboards WHERE Size ='mATX'";
    }
    if(ListCases.mboardsize == "ATX")
    {
        query="SELECT * FROM Motherboards WHERE Size ='ATX'";
    }
    Cursor cursor = mDatabase.rawQuery(query, null);
    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
        mbs = new Motherboards(cursor.getInt(0), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), mainmenu.motherboard_btn_state);
        mbsList.add(mbs);
        cursor.moveToNext();
    }
    cursor.close();
    closeDatabase();
    return mbsList;
}


}

Answer 1

错误比较

==

- ＆GT;

.equals("string");

Android Studio无法获得正确的SQL查询

1 个答案: