登录—转换页面 案例

登录界面：

转换界面：

登陆界面：

package com.example.kaohe_one;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.text.method.HideReturnsTransformationMethod;
import android.text.method.PasswordTransformationMethod;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    //创建账号和密码
    EditText yonghuming;
    EditText mima;
    Button denglu;
    CheckBox xianshimima;
    //登陆的账号和密码
    String name = "admin";
    String pwd = "123456";
    //定义String类型的usernumble和password
    String usernumber;
    String password;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获取id，获取输入的账号和密码
        yonghuming = findViewById(R.id.yonghuming);
        mima = findViewById(R.id.mima);
        denglu = findViewById(R.id.denglu);
        xianshimima = findViewById(R.id.xianshimima);

        //账号
        yonghuming.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) { }
            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) { }
            @Override
            public void afterTextChanged(Editable editable) {
                usernumber = yonghuming.getText().toString();
            }
        });
        //密码
        mima.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) { }
            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) { }
            @Override
            public void afterTextChanged(Editable editable) {
                password = mima.getText().toString();
            }
        });

        //登录按键
        denglu.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                 if (yonghuming.getText().toString().isEmpty() || mima.getText().toString().isEmpty()){
                     Toast.makeText(MainActivity.this, "账号或密码为空", Toast.LENGTH_SHORT).show();
                 }else if (usernumber.equals(name) && password.equals(pwd)) {
                         Toast.makeText(MainActivity.this, "登录成功", Toast.LENGTH_SHORT).show();
                         Intent intent = new Intent(MainActivity.this, two_main.class);
                         startActivity(intent);
                } else {
                    Toast.makeText(MainActivity.this, "账号或密码错误", Toast.LENGTH_SHORT).show();
                }
            }
        });

        //密码显示勾选框
        xianshimima.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
                if (b) {
                    //显示密码
                    mima.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
                } else {
                    //隐藏密码
                    mima.setTransformationMethod(PasswordTransformationMethod.getInstance());
                }
            }
        });
    }
}

1.添加背景的代码最好放在最外面那一层代码中，避免背景不能覆盖完全
2.定义变量的类型时，用户名和密码尽量都是String类型，这样的话自定义用户名和密码时就可以时任意字符了；之后要从监听器中得到值的变量类型要用ExitText, Button, CheckBox等

    //创建账号和密码
    EditText yonghuming;
    EditText mima;
    Button denglu;
    CheckBox xianshimima;
    //登陆的账号和密码
    String name = "admin";
    String pwd = "123456";
    //定义String类型的usernumble和password
    String usernumber;
    String password;

//赋值
yonghuming = findViewById(R.id.yonghuming);
mima = findViewById(R.id.mima);
denglu = findViewById(R.id.denglu);
xianshimima = findViewById(R.id.xianshimima);

3.用addTextChangedListener方法来获取在虚拟机中输入的用户名和密码
4.登录按键用setOnClickListener方法
5.密码勾选框用setOnCheckedChangeListener方法
6.判断输入框中的内容是否为空用isEmpty()方法