试试这个:
在你DatabaseHelper,把这个方法...
public String Exist(String user) {
String username="";
SQLiteDatabase db = this.getReadableDatabase();
try {
Cursor c = db.query(TABLE_USER, null, KEY_USER + "=?", new String[]{String.valueOf(user)},null, null, null);
if (c == null) {
return username;
}
else {
c.moveToFirst();
username = c.getString(c.getColumnIndex(KEY_USER));
}
}
catch(Exception e){
e.printStackTrace();
}
return username;
}
然后在onClickListener,试图调用您在DatabaseHelper创建方法。试试这个代码:
String myUser = txtUser.getText().toString();
String storedUser = db.Exist(myUser);
//If Username exist
if (myUser.equals(storedUser)){
Toast.makeText(getApplicationContext(), "Username already exist!", Toast.LENGTH_SHORT).show();
结帐我的答案在这里: http://stackoverflow.com/questions/27597922/android-sqlite-check-if-row-exists-in-table/43849296#43849296 – 2017-05-08 13:51:07