4.15 Android Studio一个连接SQLite数据库的登录注册实现

1、先看一下项目目录：

2、新建一个AS项目，创建如上图所示的目录结构，然后添加内容：
（1）修改添加布局文件：

activity_main.xml：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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=".LoginActivity">

<Button
android:id="@+id/register"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="注册" />
</LinearLayout>
</TableRow>
</TableLayout>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
activity_register.xml：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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=".RegisterActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:text="欢迎进入注册界面!"
android:textSize="30dp"
android:textStyle="bold" />

</LinearLayout>
</android.support.constraint.ConstraintLayout>
（2）在service包DatabaseHelper中添加链接AS自带数据库以及创建表的语句：

package com.example.sqlitelogin.service;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {
static String name="user.db";
static int dbVersion=1;
public DatabaseHelper(Context context) {
super(context, name, null, dbVersion);
}

public void onCreate(SQLiteDatabase db) {
String sql="create table user(id integer primary key autoincrement,username varchar(20),password varchar(20),age integer,sex varchar(2))";
db.execSQL(sql);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

（3）在service包UserService中用sql语句写登录注册功能的实现：

package com.example.sqlitelogin.service;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import com.example.sqlitelogin.User;

public class UserService {
private DatabaseHelper dbHelper;
public UserService(Context context){
dbHelper=new DatabaseHelper(context);
}

public boolean login(String username,String password){
SQLiteDatabase sdb=dbHelper.getReadableDatabase();
String sql="select * from user where username=? and password=?";
Cursor cursor=sdb.rawQuery(sql, new String[]{username,password});
if(cursor.moveToFirst()==true){
cursor.close();
return true;
}
return false;
}
public boolean register(User user){
SQLiteDatabase sdb=dbHelper.getReadableDatabase();
String sql="insert into user(username,password,age,sex) values(?,?,?,?)";
Object obj[]={user.getUsername(),user.getPassword(),user.getAge(),user.getSex()};
sdb.execSQL(sql, obj);
return true;
}
}

（4）在User文件中声明要用到的表列名的变量，并对其添加get&&set方法：

package com.example.sqlitelogin;

import java.io.Serializable;

public class User implements Serializable{
private int id;
private String username;
private String password;
private int age;
private String sex;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(String username, String password, int age, String sex) {
super();
this.username = username;
this.password = password;
this.age = age;
this.sex = sex;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password="
+ password + ", age=" + age + ", sex=" + sex + "]";
}

}

（5）为注册功能添加activity组件：

package com.example.sqlitelogin;

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

import com.example.sqlitelogin.service.UserService;

public class RegisterActivity extends AppCompatActivity {

EditText username;
EditText password;
EditText age;
RadioGroup sex;
Button register;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
findViews();
register.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String name=username.getText().toString().trim();
String pass=password.getText().toString().trim();
String agestr=age.getText().toString().trim();
String sexstr=((RadioButton)RegisterActivity.this.findViewById(sex.getCheckedRadioButtonId())).getText().toString();
Log.i("TAG",name+"_"+pass+"_"+agestr+"_"+sexstr);
UserService uService=new UserService(RegisterActivity.this);
User user=new User();
user.setUsername(name);
user.setPassword(pass);
user.setAge(Integer.parseInt(agestr));
user.setSex(sexstr);
uService.register(user);
Toast.makeText(RegisterActivity.this, "注册成功", Toast.LENGTH_LONG).show();
}
});
}
private void findViews() {
username=(EditText) findViewById(R.id.usernameRegister);
password=(EditText) findViewById(R.id.passwordRegister);
age=(EditText) findViewById(R.id.ageRegister);
sex=(RadioGroup) findViewById(R.id.sexRegister);
register=(Button) findViewById(R.id.Register);
}

}

（6）为登录功能添加activity组件：

package com.example.sqlitelogin;

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

import com.example.sqlitelogin.service.UserService;

public class LoginActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);//即activity_login.xml
findViews();
}
private EditText username;
private EditText password;
private Button login;
private Button register;

private void findViews() {
username=(EditText) findViewById(R.id.username);
password=(EditText) findViewById(R.id.password);
login=(Button) findViewById(R.id.login);
register=(Button) findViewById(R.id.register);

login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String name=username.getText().toString();
System.out.println(name);
String pass=password.getText().toString();
System.out.println(pass);

Log.i("TAG",name+"_"+pass);
UserService uService=new UserService(LoginActivity.this);
boolean flag=uService.login(name, pass);

if(flag){
Log.i("TAG","登录成功");
Toast.makeText(LoginActivity.this, "登录成功", Toast.LENGTH_LONG).show();
Intent intent = new Intent(LoginActivity.this,RegisterActivity.class);
startActivity(intent);
}else{
Log.i("TAG","登录失败");
Toast.makeText(LoginActivity.this, "登录失败", Toast.LENGTH_LONG).show();
}
}
});
register.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent=new Intent(LoginActivity.this,RegisterActivity.class);
startActivity(intent);
}
});
}
}

3、Androidmanifest.xml清单文件中，程序运行必备的内容一般都已经自动完成添加了。也可以进行修改：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sqlitelogin">

</activity>

</manifest>
4、在模拟器或者真机运行程序，即可！一个连接数据库的登录注册功能已经实现，效果如下：

补：
如果登录、注册的两个布局文件的 Preview 视图标红，将 android.support.constraint.ConstraintLayout 替换为 LinearLayout 即可

转自：https://blog.csdn.net/WU2629409421perfect/article/details/90313146?utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-4.control&dist_request_id=1332041.13974.16192706388769351&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-4.control