andriid基础用户登录验证，弹窗，设置标题（详解）

本文适合刚接触Android开发的读者 下面是详细代码：

package com.zhihuishu.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
EditText User_Name;
EditText User_Pass;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setTitle("未注册");//设置标题
User_Name = (EditText) findViewById(R.id.User_Name);//获取控件中的内容
User_Pass = (EditText) findViewById(R.id.User_Pass);
Button Button_regist = (Button) findViewById(R.id.Button_regist);
Button_regist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(!checkSN(User_Name.getText().toString().trim(),User_Pass.getText().toString().trim()) )
{
// Toast.makeText(MainActivity.this,"用户名或密码不能为空",Toast.LENGTH_SHORT).show();//弹框
}
}
});


}


private boolean checkSN(String username, String sn) {
try {
if ((username == null) || (username.length() ==0)) {
Toast.makeText(MainActivity.this,"用户名不能为空",Toast.LENGTH_SHORT).show();//弹框
return false;
}

else if((sn == null) || (sn.length() ==0))
{
Toast.makeText(MainActivity.this,"密码不能为空",Toast.LENGTH_SHORT).show();//弹框
return false;
}
else if(username.equals("123"))
{
Toast.makeText(MainActivity.this,"注册成功",Toast.LENGTH_SHORT).show();//弹框
}
else
{
Toast.makeText(MainActivity.this,"用户名或密码错误",Toast.LENGTH_SHORT).show();//弹框
}

} catch (Exception e) {
e.printStackTrace();
return false;
}
return true;


}
}