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一个小小的demo,希望能帮到大家
1.首先创建数据库
DatabaseHelper.java
- package com.example.login;
-
- import android.content.ContentValues;
- import android.content.Context;
- import android.database.sqlite.SQLiteDatabase;
- import android.database.sqlite.SQLiteOpenHelper;
-
- import androidx.annotation.Nullable;
-
- public class DatebaseHelper extends SQLiteOpenHelper {
- private static final String DATABASE_NAME = "login.db";
- private static final int DATABASE_VERSION = 1;
- 、、创建数据库
- public DatebaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
- super(context, DATABASE_NAME, factory, DATABASE_VERSION);
- }
- //创建数据库表
- @Override
- public void onCreate(SQLiteDatabase db) {
- db.execSQL("create table username( id varchar(10) primary key AUTOINCREMENT, name varchar(30), password varchar(30))");
- }
- //添加数据
- public void addData(SQLiteDatabase sqLiteDatabase, String name, String password) {
- ContentValues values = new ContentValues();
- values.put("name", name);
- values.put("password", password);
- sqLiteDatabase.insert("user", null, values);
- }
-
- @Override
- public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-
- }
- }
MainActivity.java
- package com.example.login;
-
- import android.annotation.SuppressLint;
- import android.content.Intent;
- import android.database.Cursor;
- import android.database.SQLException;
- import android.database.sqlite.SQLiteDatabase;
- import android.database.sqlite.SQLiteException;
- import android.os.Bundle;
- import android.view.View;
- import android.widget.Button;
- import android.widget.EditText;
- import android.widget.Toast;
-
- import androidx.appcompat.app.AlertDialog;
- import androidx.appcompat.app.AppCompatActivity;
-
- public class MainActivity extends AppCompatActivity {
-
- private static final String DATABASE_NAME = "login.db";
- private static final int DATABASE_VERSION = 1;
- private static final String TABLE_NAME = "username";
- private SQLiteDatabase db;
- private Button btn_l, btn_r;
- private EditText nameText, passText;
- private Intent intent;
-
- public MainActivity() {
- }
-
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
-
- DatebaseHelper databaseHelper = new DatebaseHelper(MainActivity.this, DATABASE_NAME, null, DATABASE_VERSION);
- db = databaseHelper.getWritableDatabase();
-
- nameText = findViewById(R.id.username);
- passText = findViewById(R.id.password);
-
- btn_l = findViewById(R.id.login);
- btn_r = findViewById(R.id.register);
-
- btn_r.setOnClickListener(v -> {
- intent = new Intent(MainActivity.this, RegisterActivaty.class);
- startActivity(intent);
- });
- btn_l.setOnClickListener(new LoginListener());
- }
-
- private class LoginListener implements View.OnClickListener {
- @Override
- public void onClick(View v) {
- String nameString = nameText.getText().toString();
- String passString = passText.getText().toString();
- if ("".equals(nameString) || "".equals(passString)) {
- Toast.makeText(MainActivity.this, "用户名或密码不能为空", Toast.LENGTH_SHORT).show();
- } else {
- isUserinfo(nameString, passString);
- }
- }
- }
-
- private void isUserinfo(String name, String pass) {
- String passString = pass;
- try {
- @SuppressLint("Recycle") Cursor cursor = db.query(TABLE_NAME, new String[]{"name", "password"}, "name=?", new String[]{name}, null, null, "password");
- while (cursor.moveToNext()) {
- @SuppressLint("Range") String password = cursor.getString(cursor.getColumnIndex("password"));
- cursor.close();
- if (passString.equals(password)) {
- new AlertDialog.Builder(MainActivity.this).setTitle("正确")
- .setMessage("成功登录").setPositiveButton("确定", (dialog, which) -> {
- // TODO Auto-generated method stub
- Intent a = new Intent(MainActivity.this, MainActivity.class);
- startActivity(a);
- }).show();
- break;
- } else {
- Toast.makeText(this, "用户名密码不正确", Toast.LENGTH_LONG).show();
- break;
- }
- }
- } catch (SQLiteException e) {
- CreatTable();
- }
- }
-
- private void CreatTable() {
- String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME
- + " (name varchar(30) primary key,password varchar(30));";
- try {
- db.execSQL(sql);
- } catch (SQLException ignored) {
- }
- }
- }
注册实现 RegisterActivity.java
- package com.example.login;
-
- import android.app.Activity;
- import android.content.Intent;
- import android.database.Cursor;
- import android.database.sqlite.SQLiteDatabase;
- import android.os.Bundle;
- import android.text.TextUtils;
- import android.view.Window;
- import android.widget.Button;
- import android.widget.EditText;
- import android.widget.Toast;
-
- /**
- * @author ts
- */
- public class RegisterActivaty extends Activity {
- private EditText edittext1, edittext2, edittext3;
- private DatebaseHelper databaseHelper;
- private static final String DATABASE_NAME = "login.db";
- private static final int DATABASE_VERSION = 1;
- private SQLiteDatabase db;
-
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- this.requestWindowFeature(Window.FEATURE_NO_TITLE);
- setContentView(R.layout.activity_register);
- databaseHelper = new DatebaseHelper(RegisterActivaty.this, DATABASE_NAME, null, DATABASE_VERSION);
- db = databaseHelper.getReadableDatabase();
-
- edittext1 = findViewById(R.id.username);
- edittext2 = findViewById(R.id.editview2);
- edittext3 = findViewById(R.id.password);
-
- Button button = findViewById(R.id.tijiao);
- button.setOnClickListener(v -> {
- String namestring = edittext1.getText().toString();
- String passstring = edittext2.getText().toString();
- String repassstring = edittext3.getText().toString();
-
- submit(namestring, passstring, repassstring);
-
- });
- }
- //判空
- private void submit(String namestring, String passstring, String repassstring) {
- if (TextUtils.isEmpty(namestring)) {
- Toast.makeText(this, "用户名不能为空", Toast.LENGTH_SHORT).show();
- return;
- }
-
- if (TextUtils.isEmpty(passstring)) {
- Toast.makeText(this, "密码不能为空", Toast.LENGTH_SHORT).show();
- return;
- }
-
- if (TextUtils.isEmpty(repassstring)) {
- Toast.makeText(this, "确认密码不能为空", Toast.LENGTH_SHORT).show();
- return;
- }
-
- if (!notexistSameName(namestring)) {
- Toast.makeText(this, "用户名已存在", Toast.LENGTH_SHORT).show();
- } else if (passstring.equals(repassstring)) {
- db.execSQL("insert into username (name,password) values(?,?)", new String[]{namestring, passstring});
- Toast.makeText(RegisterActivaty.this, "注册成功!", Toast.LENGTH_LONG).show();
- Intent b = new Intent(RegisterActivaty.this, MainActivity.class);
- startActivity(b);
- } else {
- Toast.makeText(RegisterActivaty.this, "两次密码不一致", Toast.LENGTH_LONG).show();
- }
- }
- //通过查询数据库判断用户名是否存在
- private boolean notexistSameName(String name) {
- Cursor cursor = db.query("username", new String[]{"name"}, "name = ?", new String[]{name}, null, null, null);
- if (cursor.getCount() == 0) {
- cursor.close();
- return true;
- } else {
- cursor.close();
- return false;
- }
- }
-
- }
效果图
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