01每日打卡 3月15日

今天开始正式的每日打卡的开发，首先进行了登录界面的开发，运用了sharepreference对象来存储登录信息，保证了登录只需输入一次账号和密码。

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    EditText name,pwd;
    Button btnlogin,btnreg,teacher;
    Mysql mysql;
    SQLiteDatabase db;
    SharedPreferences sp1,sp2,sp3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        name = this.findViewById(R.id.name);            //用户名输入框
        pwd = this.findViewById(R.id.pwd);              //密码输入框
        btnlogin = this.findViewById(R.id.login);         //登录按钮
        btnreg = this.findViewById(R.id.reg);               //注册按钮
        teacher=this.findViewById(R.id.teacher);
        sp1 =  this.getSharedPreferences("userinfo",this.MODE_PRIVATE);
        sp2 = this.getSharedPreferences("username",this.MODE_PRIVATE);

        sp3 = this.getSharedPreferences("user",this.MODE_PRIVATE);

        boolean islogin= sp3.getBoolean("islogin",false);

        name.setText(sp1.getString("usname",null));
        pwd.setText(sp1.getString("uspwd",null));
        mysql = new Mysql(this,"Userinfo",null,1);      //建数据库或者取数据库
        db = mysql.getReadableDatabase();

        if(islogin==false){
            btnlogin.setOnClickListener(new View.OnClickListener() {                //登录事件
                @Override
                public void onClick(View v) {
                    String username = name.getText().toString();
                    String password = pwd.getText().toString();                 //获取用户输入的用户名和密码
                    //查询用户名和密码相同的数据
                    Cursor cursor = db.query("logins",new String[]{"usname","uspwd"}," usname=? and uspwd=?",new String[]{username,password},null,null,null);

                    int flag = cursor.getCount();                            //查询出来的记录项的条数，若没有该用户则为0条
                    if(flag!=0){                                            //若查询出的记录不为0，则进行跳转操作
                        Intent intent = new Intent();
                        intent.setClass(MainActivity.this,add.class);            //设置页面跳转
                        SharedPreferences.Editor editor = sp2.edit();
                        cursor.moveToFirst();                                   //将光标移动到position为0的位置，默认位置为-1
                        String loginname = cursor.getString(0);
                        editor.putString("Loginname",loginname);
                        editor.commit();

                        SharedPreferences.Editor editor1 = sp3.edit();
                        editor1.putBoolean("islogin",true);
                        editor1.commit();
                                                                            //将用户名存到SharedPreferences中
                        startActivity(intent);
                    }
                    else{
                        Toast.makeText(MainActivity.this,"用户名或密码错误！",Toast.LENGTH_LONG).show();             //提示用户信息错误或没有账号
                    }

                }
            });
        }

        else{
            startActivity(new Intent(MainActivity.this, add.class));
            finish();
        }






        btnreg.setOnClickListener(new View.OnClickListener() {                  //注册事件
            @Override
            public void onClick(View v) {

                Intent intent = new Intent();
                intent.setClass(MainActivity.this,Register.class);          //跳转到注册页面
                startActivity(intent);
                Toast.makeText(MainActivity.this,"前往注册！",Toast.LENGTH_SHORT).show();
            }
        });
        teacher.setOnClickListener(new View.OnClickListener() {                  //注册事件
            @Override
            public void onClick(View v) {

                Intent intent = new Intent();
                intent.setClass(MainActivity.this,teacher.class);          //跳转到注册页面
                startActivity(intent);
                Toast.makeText(MainActivity.this,"教师登录！",Toast.LENGTH_SHORT).show();
            }
        });

    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:layout_editor_absoluteX="71dp"
        tools:layout_editor_absoluteY="0dp">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:orientation="horizontal">

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="0.3"
                android:gravity="center"
                android:text="用户名:"
                android:textSize="18dp" />

            <EditText
                android:id="@+id/name"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginRight="20dp"
                android:layout_weight="1" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:orientation="horizontal">

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="0.3"
                android:gravity="center"
                android:text="密    码:"
                android:textSize="18dp" />

            <EditText
                android:id="@+id/pwd"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginRight="20dp"
                android:layout_weight="1"
                android:inputType="textPassword" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal">

            <Button
                android:id="@+id/login"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:text="登录" />

            <Button
                android:id="@+id/reg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:text="注册" />
        </LinearLayout>

        <Button
            android:id="@+id/teacher"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:textColor="@color/white"
            android:background="@color/light_blue"
            android:text="教师登录" />
    </LinearLayout>


</androidx.constraintlayout.widget.ConstraintLayout>