Question

我试图登录表单：

TextView tv = (TextView) findViewById(R.id.btnRegister);
    tv.setClickable(true);
    tv.setMovementMethod(LinkMovementMethod.getInstance());
    tv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this, Register.class));
        }
});

username=(EditText)findViewById(R.id.Uname);
password=(EditText)findViewById(R.id.Pword);
party=username.getText().toString();
p2=password.getText().toString();
ok=(Button)findViewById(.id.btnLogin);

ok.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        if(party.isEmpty() && p2.isEmpty()){
            Toast.makeText(MainActivity.this, "empty fields", Toast.LENGTH_SHORT).show();
            return;
        } else if(!party.isEmpty() && !p2.isEmpty()){
            db.execSQL("select * from Students where Name='"+party+"'and Password='"+p2+"'");
            Toast.makeText(MainActivity.this, "Welcome", Toast.LENGTH_SHORT).show();
            startActivity(new Intent(MainActivity.this,Welcome.class));
        }
    }
});

当我输入用户名和密码时，我会用toast显示＆＃34;空字段＆＃34;每当我点击登录时，它都会显示空字段：

Answer 1

尝试长度

if(party.toString().trim().length < 0 && p2.toString().trim().length < 0){

Toast.makeText(MainActivity.this, "empty fields", Toast.LENGTH_SHORT).show();

return;

}else {

db.execSQL("select * from Students where Name='"+party+"'and Password='"+p2+"'");

Toast.makeText(MainActivity.this, "Welcome", Toast.LENGTH_SHORT).show();

startActivity(new Intent(MainActivity.this,Welcome.class));

}

Answer 2

const y = f => { const g = self => x => f(self(self))(x); return g(g);}

Answer 3

请为我尝试这项工作。

 if (TextUtils.isEmpty(party) || TextUtils.isEmpty(p2)) {
        Toast.makeText(MainActivity.this, "empty fields", Toast.LENGTH_SHORT).show();
    } else

    {
        db.execSQL("select * from Students where Name='" + party + "'and Password='" + p2 + "'");
        Toast.makeText(MainActivity.this, "Welcome", Toast.LENGTH_SHORT).show();
        startActivity(new Intent(MainActivity.this, Welcome.class));
    }

Android Studio登录表单

3 个答案: