如何从android studio的sqlite数据库中删除用户？

Question

我试图弄清楚如何通过在编辑文本中输入用户的用户名并单击删除来一次删除一个用户，然后我希望从中删除所有用户信息（用户名、用户名、密码、生日、电话、地址）数据库。 下面是我的代码，由于某种原因它不起作用，请任何人帮助我！！ 我非常绝望，我几个小时都在试图找出问题所在。

DatabaseHelperUser 类：

public class DatabaseHelperUser extends SQLiteOpenHelper {

public static final String DATABASE_NAME = "User.db";
public static final String TABLE_NAME = "User_table";
public static final String COL1 = "ID";
public static final String COL2 = "UserNum";
public static final String COL3 = "UserName";
public static final String COL4 = "Password";
public static final String COL5 = "BirthDate";
public static final String COL6 = "Phone";
public static final String COL7 = "Address";


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


@Override
public void onCreate(SQLiteDatabase db) {

    db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, UserNum TEXT,UserName Text,Password Text,BirthDate Text,Phone Text,Address Text)");

}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {

    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

public Cursor getData() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("select * from " + TABLE_NAME, null);
    return res;
}

public boolean deleteData(String UserName) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete(TABLE_NAME, "UserName" + "=?" + UserName, null) > 0;

}


}

RemoveUser 类：

public class RemoveUser extends AppCompatActivity {

Button btdelete;
EditText txtUser;

DatabaseHelperUser myDb;

private String selectedName;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_remove_user);

    btdelete = (Button) findViewById(R.id.butRemove);
    txtUser = (EditText) findViewById(R.id.etxtUserName);


    myDb = new DatabaseHelperUser(this);

    btdelete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            boolean delete = myDb.deleteData(txtUser.getText().toString());

            if(delete == true)
            Toast.makeText(RemoveUser.this,"User has been deleted", Toast.LENGTH_LONG).show();

            else
                Toast.makeText(RemoveUser.this,"User has not been deleted", Toast.LENGTH_LONG).show();

        }
    });


}
}

Answer 1

您必须将变量UserName作为方法delete()的 3d 参数传递，以便它将替换占位符? 执行语句时：

public boolean deleteData(String UserName) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete(TABLE_NAME, "UserName = ?", new String[] {UserName}) > 0;
}