<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:background="@drawable/background"

    android:orientation="vertical"

    tools:context=".MainActivity">

    <EditText

        android:id="@+id/username"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="QQ号/手机号/邮箱"

        android:layout_marginTop="300dp"/>

    <EditText

        android:id="@+id/password"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="密码"

        android:layout_marginTop="20dp"/>

    <ImageButton

        android:id="@+id/login"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:src="@drawable/login"

        android:layout_gravity="center"/>

</LinearLayout>

public class MainActivity extends AppCompatActivity {

    //定义后台账号和密码

    private String name = "fxz", pwd = "123";

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //获取编辑框用户名和密码

        EditText username_EditText = findViewById(R.id.username);

        EditText password_EditText = findViewById(R.id.password);

        //获取登录按键

        ImageButton login = findViewById(R.id.login);

        //获取Shared Preferences对象

        final SharedPreferences sharedPreferences = getSharedPreferences("qqAutoLogin", MODE_PRIVATE);

        /**********实现自动登录功能************/

        //获取账号信息

        String username = sharedPreferences.getString("username", null);

        String password = sharedPreferences.getString("password", null);

        //判断用户名和密码是否为空

        if (username != null && password != null) {

            //如果用户名和密码相同，实现自动登录

            if (username.equals(name) && password.equals(pwd)) {

                //通过Intent跳转登录

                Intent intent = new Intent(MainActivity.this, MessageActivity.class);

                //启动跳转界面

                startActivity(intent);

            }

        } else {

            /**********实现手动登录并储存账号和密码************/

            login.setOnClickListener(new View.OnClickListener() {

                @Override

                public void onClick(View v) {

                    //获取输入的账号和密码

                    String local_username=username_EditText.getText().toString();

                    String local_password=password_EditText.getText().toString();

                    //获取Editor对象

                    SharedPreferences.Editor editor=sharedPreferences.edit();

                    if(local_username.equals(name) && local_password.equals(pwd)){

                        //这里保存账号和密码并提交有些多余

                        editor.putString("username",local_username);

                        editor.putString("password",local_password);

                        //提交信息

                        editor.commit();

                        //通过Intent跳转登录

                        Intent intent = new Intent(MainActivity.this, MessageActivity.class);

                        //启动跳转界面

                        startActivity(intent);

                        Toast.makeText(MainActivity.this, "已保存账号和密码", Toast.LENGTH_SHORT).show();

                    }else{

                        Toast.makeText(MainActivity.this, "账号和密码错误", Toast.LENGTH_SHORT).show();

                    }

                }

            });

        }

    }

}