每日总结之app的登录
重点：activity之间的跳转，以及sqliteopenhelper的使用
自定义一个mysqliteeopenhelper类继承与静态的sqliteopenhelper；
package com.example.myapplication; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import androidx.annotation.Nullable; import com.example.myapplication.javabean.User; public class Mysqliteopenhelper extends SQLiteOpenHelper { private static final String DB_NAME="Mysqlite.db"; private static final String creat_users="create table users(name varchar(32),password varchar(32))"; public Mysqliteopenhelper(@Nullable Context context) { super(context, DB_NAME, null, 1); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(creat_users); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } public long Register(User u) { /* getReadableDatabase()方法则是先以读写方式打开数据库 如果数据库的磁盘空间满了，就会打开失败 当打开失败后会继续尝试以只读方式打开数据库。 如果该问题成功解决，则只读数据库对象就会关闭，然后返回一个可读写的数据库对象。 */ SQLiteDatabase db= getReadableDatabase(); //将参数name和password放入 ContentValues的实例化对象里面 ContentValues cv=new ContentValues(); cv.put("name",u.getName()); cv.put("password",u.getPassword()); //将这个对象插入到数据库 long users=db.insert("users",null,cv); return users; } public boolean login(String name,String password){ SQLiteDatabase db1= getReadableDatabase(); boolean result=false; /* 遍历表里面的每一行（按行查找） 看是否有与输入姓名一样的字段"name like ?" 若有继续查找密码 没有则查无此人 */ Cursor cursor= db1.query("users",null,"name like ?",new String[]{name},null,null,null); if(cursor!=null){ //游标锁定一行后查找该行的密码列，用getString()方法获取密码 while (cursor.moveToNext()){ String password1 = cursor.getString(1); //比较找到的密码是否和输入密码一致，返回0/1 result=password1.equals(password); return result; } } return false; } }
主页面代码：获取不同的按钮id值，文本输入值，通过Switch——case选择不同按钮调用功能函数（增删改查）的功能,可以通过main.xml文件对按钮添加点击监听事件，也可以添加onCilck添加对应函数
package com.example.myapplication; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; 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 implements View.OnClickListener { private Button login,register; private EditText name,password; private Mysqliteopenhelper mysqliteopenhelper; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mysqliteopenhelper=new Mysqliteopenhelper(this); find(); } private void find() { login=findViewById(R.id.login); register=findViewById(R.id.register); name=findViewById(R.id.ename); password=findViewById(R.id.epassword); login.setOnClickListener(this); register.setOnClickListener(this); } @Override public void onClick(View v) { int id=v.getId(); switch (id){ case R.id.login: String s=name.getText().toString(); String ss=password.getText().toString(); boolean login= mysqliteopenhelper.login(s,ss); if (login){ Toast.makeText(this,"登陆成功",Toast.LENGTH_SHORT).show(); Intent intent = new Intent(this,good.class); startActivity(intent); }else { Toast.makeText(this,"登陆失败",Toast.LENGTH_SHORT).show(); } break; case R.id.register: Intent intent1= new Intent(this,register.class); startActivity(intent1); break; } } }
<?xml version="1.0" encoding="utf-8"?> <LinearLayout 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" android:orientation="vertical" tools:context=".MainActivity"> <View android:layout_width="match_parent" android:layout_height="120dp" /> <LinearLayout android:layout_width="match_parent" android:layout_height="80dp" android:orientation="horizontal"> <TextView android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" android:text="账号" android:id="@+id/name" android:textSize="30dp" android:gravity="center_vertical"/> <EditText android:id="@+id/ename" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="3" android:hint="请输入用户名"/> </LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="80dp" android:orientation="horizontal"> <TextView android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" android:text="密码" android:id="@+id/password" android:textSize="30dp" android:gravity="center_vertical"/> <EditText android:id="@+id/epassword" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="3" android:hint="请输入用密码"/> </LinearLayout> <Button android:layout_width="160dp" android:layout_height="80dp" android:text="登录" android:textSize="30dp" android:background="@color/colorAccent" android:layout_gravity="center" android:id="@+id/login"/> <Button android:layout_width="160dp" android:layout_height="80dp" android:text="注册" android:textSize="30dp" android:background="@color/colorAccent" android:layout_gravity="center" android:id="@+id/register"/> </LinearLayout>
注册活动：
package com.example.myapplication; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.Toast; import com.example.myapplication.javabean.User; public class register extends AppCompatActivity { private Button register1; private EditText name1,password1; private Mysqliteopenhelper mysqliteopenhelper1; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_register); mysqliteopenhelper1=new Mysqliteopenhelper(this); find(); } private void find() { register1=findViewById(R.id.register1); name1=findViewById(R.id.ename1); password1=findViewById(R.id.epassword1); } public void zhuce(View view) { String s=name1.getText().toString(); String ss=password1.getText().toString(); User user = new User(s,ss); long l=mysqliteopenhelper1.Register(user); if(l!=-1){ Toast.makeText(this,"注册成功",Toast.LENGTH_SHORT).show(); Intent intent3=new Intent(this,MainActivity.class); startActivity(intent3); }else{ Toast.makeText(this,"注册失败",Toast.LENGTH_SHORT).show(); } } }
