我想在android中搜索我的数据库中的用户名重复

Question

Cursor c=db.rawQuery("Select orders from table_name where usrname=username;",null);

usrname是在edittext中输入的字符串，用户名已存在于数据库中。

if(c!=null)
{
    Toast.makeText(this,"Username already exists,please use a different username",Toast.LENGTH_SHORT).show();
}

Answer 1

改变条件

NavigationView navigationView = (NavigationView) findViewById(R.id.navigationViewId);

View headerView = navigationView.inflateHeaderView(R.layout.nav_header);
CircleImageView drawerHeaderImage = (CircleImageView) headerView.findViewById(R.id.circularImageId);
TextView user = (TextView) headerView.findViewById(R.id.loginTextId);

Answer 2

Cursor c=db.rawQuery("Select orders from table_name where usrname=yourusername",null);
if(c.getcount>0)
{
    Toast.makeText(this,"Username already exists,please use a different username",Toast.LENGTH_SHORT).show();
}