Android Studio如何通过结合SQLite数据库实现简单的注册，登录功能。
第一步：创建一个活动DatabaseHelper.java；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;
public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "user.db";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_USERS = "users";
private static final String COLUMN_ID = "id";
private static final String COLUMN_USERNAME = "username";
private static final String COLUMN_PASSWORD = "password";
private static final String COLUMN_PHONE_NUMBER = "phone_number";
private static final String COLUMN_ADDRESS = "address";
private static final String CREATE_TABLE_USERS =
"CREATE TABLE " + TABLE_USERS + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
COLUMN_USERNAME + " TEXT NOT NULL UNIQUE, " +
COLUMN_PASSWORD + " TEXT NOT NULL, " +
COLUMN_PHONE_NUMBER + " TEXT, " +
COLUMN_ADDRESS + " TEXT" +
")";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_USERS);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS);
onCreate(db);
}
/*@SuppressLint("Range")*/
public long insertUser(String username, String password, String phoneNumber, String address) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_USERNAME, username);
values.put(COLUMN_PASSWORD, password);
values.put(COLUMN_PHONE_NUMBER, phoneNumber);
values.put(COLUMN_ADDRESS, address);
long result = db.insert(TABLE_USERS, null, values);
db.close();
return result;
}
public boolean checkUserExist(String username) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_USERS, new String[]{COLUMN_ID},
COLUMN_USERNAME + "=?", new String[]{username},
null, null, null);
boolean exists = cursor.getCount() > 0;
cursor.close();
db.close();
return exists;
}
public boolean checkUserExist(String username, String password) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_USERS, new String[]{COLUMN_ID},
COLUMN_USERNAME + "=? AND " + COLUMN_PASSWORD + "=?",
new String[]{username, password},
null, null, null);
boolean exists = cursor.getCount() > 0;
cursor.close();
db.close();
return exists;
}
}
第二步：创建一个活动RegisterActivity.java；
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class RegisterActivity extends AppCompatActivity {
EditText etUsername, etPassword, etPhoneNumber, etAddress;
Button btnRegister;
DatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
etUsername = findViewById(R.id.etUsername);
etPassword = findViewById(R.id.etPassword);
etPhoneNumber = findViewById(R.id.etPhoneNumber);
etAddress = findViewById(R.id.etAddress);
btnRegister = findViewById(R.id.btnRegister);
dbHelper = new DatabaseHelper(this);
btnRegister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username = etUsername.getText().toString();
String password = etPassword.getText().toString();
String phoneNumber = etPhoneNumber.getText().toString();
String address = etAddress.getText().toString();
if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {
Toast.makeText(RegisterActivity.this, "用户名和密码不能为空", Toast.LENGTH_SHORT).show();
return;
}
if (dbHelper.checkUserExist(username)) {
Toast.makeText(RegisterActivity.this, "该用户名已被注册", Toast.LENGTH_SHORT).show();
return;
}
long result = dbHelper.insertUser(username, password, phoneNumber, address);
if (result != -1) {
Toast.makeText(RegisterActivity.this, "注册成功", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(RegisterActivity.this, LoginActivity.class);
startActivity(intent);
} else {
Toast.makeText(RegisterActivity.this, "注册失败", Toast.LENGTH_SHORT).show();
}
}
});
}
} 第三步：创建一个activity_register.xml布局文件；
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="注册"
android:textSize="24sp"
android:textStyle="bold" />
<EditText
android:id="@+id/etUsername"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="用户名" />
<EditText
android:id="@+id/etPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="密码"
android:inputType="textPassword" />
<EditText
android:id="@+id/etPhoneNumber"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="电话号码"
android:inputType="phone" />
<EditText
android:id="@+id/etAddress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="地址" />
<Button
android:id="@+id/btnRegister"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="16dp"
android:text="注册" />
</LinearLayout> 第四步：创建一个活动LoginActivity.java;
该活动登录成功后，会通过代码中的（意图）Intent跳转到MainActivity.java,读者可根据自己的需求更改代码，从而改变跳转的活动文件java的位置。
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
public class LoginActivity extends AppCompatActivity {
EditText etUsername, etPassword;
Button btnLogin;
DatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
etUsername = findViewById(R.id.etUsername);
etPassword = findViewById(R.id.etPassword);
btnLogin = findViewById(R.id.btnLogin);
dbHelper = new DatabaseHelper(this);
btnLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username = etUsername.getText().toString();
String password = etPassword.getText().toString();
if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {
Toast.makeText(LoginActivity.this, "用户名和密码不能为空", Toast.LENGTH_SHORT).show();
return;
}
if (dbHelper.checkUserExist(username, password)) {
Toast.makeText(LoginActivity.this, "登录成功", Toast.LENGTH_SHORT).show();
//创建意图
Intent intent = new Intent(LoginActivity.this,MainActivity.class);
//启动新的activity
startActivity(intent);
} else {
Toast.makeText(LoginActivity.this, "用户名或密码不正确", Toast.LENGTH_SHORT).show();
}
}
});
}
}
第五步：创建一个activity_login.xml布局文件；
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="登录"
android:textSize="24sp"
android:textStyle="bold"/>
<EditText
android:id="@+id/etUsername"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="用户名"/>
<EditText
android:id="@+id/etPassword"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:hint="密码"
android:inputType="textPassword"/>
<Button
android:id="@+id/btnLogin"
android:layout_width="wrap_content"
android:layout_height="58dp"
android:layout_gravity="center"
android:layout_margin="16dp"
android:text="登录" />
</LinearLayout> 若完成上述内容，则有下面的运行结果展示：
且注册成功后通过Intent会自动跳转到登录页面：
https://img-blog.csdnimg.cn/direct/6e8bb00af4464468818c28aecd4b97e6.pnghttps://img-blog.csdnimg.cn/direct/fc2a4a0c4f72495f9d56cace2d5cb2ec.png
完成后，可探求‘’user.db”数据库文件的位置所在：
点击右上角View->Tool Windows->Device Exploer出现如下画面：
https://img-blog.csdnimg.cn/direct/dab7e86a219247cf8e482fb37ab4179d.png
点击data->data->"packge包的位置 (活动文件java的代码开头）"->database；可检察到数据库user.db。
https://img-blog.csdnimg.cn/direct/6dea35fb900e410eb0afe6fcf47127bb.png
右键该user.db,选择save as（保存位于电脑某位置）
导入进软件SQLite Expert Personal 5.4(x64)中，即展示如下：
https://img-blog.csdnimg.cn/direct/71c48c7ff6c54423a2b0f4debd1c6d60.png
以上为通过SQLite实现一个简单的注册，登录页面的功能。
若以上存在什么问题，各人可以私信我，大概从评论区说出。
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