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收藏闪存小组博问

n1ce2cv

园龄：5年2个月粉丝：4关注：1

数据存储

SP

  • 存储配置信息：自动登录，记住密码，主题记录
  • 首选项sharedpreference不能存太多东西，程序运行时，首选项里的所有数据会全被加载
  • MainActivity.java
package com.example.mysp;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
 
    /**
     *
     *     // 参数1：sp的名字
     *     // 参数2：sp保存用的模式 常规（覆盖）、追加
     *     public SharedPreferences getSharedPreferences(String name, int mode) {
     *         throw new RuntimeException("Stub!");
     *     }
     * @param view
     */
 
    public void saveToSP(View view) {
        SharedPreferences sp = getSharedPreferences("SPtest", Context.MODE_PRIVATE);
        sp.edit().putString("haha", "哈哈").apply(); // 保存到xml
    }
 
    public void getSpData(View view) {
        SharedPreferences sp = getSharedPreferences("SPtest", Context.MODE_PRIVATE);
        String s = sp.getString("haha", "默认值");
        Log.e("wmj", "getSpData: " + s);
    }
}

通过传递context获取全局资源

  • MyData.java
package com.example.mysp3;
 
import android.content.Context;
import android.content.SharedPreferences;
 
public class MyData {
    public int number;
    private Context context;
 
    public MyData(Context context) {
        this.context = context;
    }
 
    public void save(){
        String name = context.getResources().getString(R.string.my_data);
        SharedPreferences sp = context.getSharedPreferences(name, Context.MODE_PRIVATE);
 
        SharedPreferences.Editor editor = sp.edit();
        String key = context.getResources().getString(R.string.my_key);
        editor.putInt(key, number);
        editor.apply();
    }
 
    public int load(){
        String name = context.getResources().getString(R.string.my_data);
        SharedPreferences sp = context.getSharedPreferences(name, Context.MODE_PRIVATE);
        String key = context.getResources().getString(R.string.my_key);
        int x = sp.getInt(key, 0);
        number = x;
        return x;
    }
}
  • MainActivity.java
package com.example.mysp3;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.util.Log;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        /**
         * 不能传递this，MyData保存着Activity的引用，Activity会反复创建，但无法销毁
         * 会导致内存泄漏
         */
        MyData myData = new MyData(getApplicationContext()); // myData具备访问全局资源的能力
        myData.number = 1000;
        myData.save();
        int y = myData.load();
        Log.d("wmj", "onCreate: " + y);
    }
}

自动登录

  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="用户名"/>
 
    <EditText
        android:id="@+id/et_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="密码"/>
 
    <EditText
        android:id="@+id/et_pwd"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:password="true"/>
    
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        
        <CheckBox
            android:id="@+id/cb_rememberpwd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="记住密码"/>
 
        <CheckBox
            android:id="@+id/cb_autologin"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="自动登录"/>
 
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
 
        <Button
            android:id="@+id/bt_register"
            android:text="注册"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>
 
        <Button
            android:id="@+id/bt_login"
            android:text="登录"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>
 
    </LinearLayout>
 
</LinearLayout>
  • MainActivity.java
package com.example.mysp2;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    SharedPreferences sp;
    EditText et_name, et_pwd;
    CheckBox cb_rememberpwd, cb_autologin;
    Button bt_register, bt_login;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        // 获取首选项
        sp = getSharedPreferences("config", Context.MODE_PRIVATE);
 
        initView();
 
        // 第二次打开的时候，送sp获取数据，进行画面同步
        boolean rememberpwd = sp.getBoolean("rememberpwd", false);
        boolean autologin = sp.getBoolean("autologin", false);
 
        if(rememberpwd){
            // 从sp里获取数据，并放到edittext中
            String name = sp.getString("name", "");
            String pwd = sp.getString("pwd", "");
            et_name.setText(name);
            et_pwd.setText(pwd);
            cb_rememberpwd.setChecked(true);
        }
        
        if(autologin){
            cb_autologin.setChecked(true);
            Toast.makeText(this, "自动登录", Toast.LENGTH_SHORT).show();
        }
 
    }
 
    private void initView() {
        et_name = findViewById(R.id.et_name);
        et_pwd = findViewById(R.id.et_pwd);
        cb_rememberpwd = findViewById(R.id.cb_rememberpwd);
        cb_autologin = findViewById(R.id.cb_autologin);
        bt_register = findViewById(R.id.bt_register);
        bt_login = findViewById(R.id.bt_login);
 
        // 设置监听
        MyOnClickLister myOnClickLister = new MyOnClickLister();
        bt_register.setOnClickListener(myOnClickLister);
        bt_login.setOnClickListener(myOnClickLister);
    }
 
    private class MyOnClickLister implements View.OnClickListener{
 
        @Override
        public void onClick(View view) {
            switch (view.getId()){
                case R.id.bt_register:
                    break;
                case R.id.bt_login:
                    String name = et_name.getText().toString().trim();
                    String pwd = et_pwd.getText().toString().trim();
                    if(TextUtils.isEmpty(name) || TextUtils.isEmpty(pwd)){
                        Toast.makeText(getApplicationContext(), "用户名或密码未填写", Toast.LENGTH_SHORT).show();
                    } else {
                        // 保存密码被勾选后，需要记录账号密码和勾选状态
                        if(cb_rememberpwd.isChecked()){
                            SharedPreferences.Editor editor = sp.edit();
                            editor.putString("name", name);
                            editor.putString("pwd", pwd);
                            editor.putBoolean("rememberpwd", true);
                            editor.apply();
                        }
 
                        // 自动登录被勾选
                        if(cb_autologin.isChecked()){
                            SharedPreferences.Editor editor = sp.edit();
                            editor.putBoolean("autologin", true);
                            editor.apply();
                        }
 
                    }
                    break;
                default:
                    break;
            }
        }
    }
}

SQLite

  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="createDB"
        android:text="创建db文件"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="query"
        android:text="查询"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="insert"
        android:text="插入"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="update"
        android:text="修改"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="delete"
        android:text="删除"/>
 
 
</LinearLayout>
  • MySqlOpenHelper.java
package com.example.mysqlite;
 
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
 
import androidx.annotation.Nullable;
 
// 工具类  单例模式：1.构造函数私有化 2.对外提供函数
public class MySqliteOpenHelper extends SQLiteOpenHelper {
 
    // 2.对外提供函数
    private static MySqliteOpenHelper mInstance;
    public static synchronized SQLiteOpenHelper getmInstance(Context context){
        if(mInstance == null){
            mInstance = new MySqliteOpenHelper(context, "wmj.db", null, 1);
        }
        return mInstance;
    }
 
    // 1.构造函数私有化
    private MySqliteOpenHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }
 
 
    // 数据库初始化时使用  此函数只会执行一次
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        // 创建persons表 _id, name
        String sql = "create table persons(_id integer primary key autoincrement, name text)";
        sqLiteDatabase.execSQL(sql);
    }
 
    // 数据库升级时使用
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
 
    }
}
  • MainActivity.java
package com.example.mysqlite;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
 
    public void createDB(View view) {
        SQLiteOpenHelper helper = MySqliteOpenHelper.getmInstance(this);
 
        // 文件夹的创建
        SQLiteDatabase readableDatabase = helper.getReadableDatabase();
    }
 
    public void query(View view) {
        SQLiteOpenHelper helper = MySqliteOpenHelper.getmInstance(this);
        SQLiteDatabase db = helper.getReadableDatabase();
 
        if(db.isOpen()){
            // 返回游标
            Cursor cursor = db.rawQuery("select * from persons", null);
 
            // 迭代游标，遍历数据
            while (cursor.moveToNext()){
//                int _id = cursor.getInt(0);
                int _id = cursor.getInt(cursor.getColumnIndex("_id"));
                String name = cursor.getString(cursor.getColumnIndex("name"));
 
                Log.d("wmj", "query: " + _id + " " + name);
                // 关闭
                cursor.close();
                db.close();
            }
        }
    }
 
    public void insert(View view) {
        SQLiteOpenHelper helper = MySqliteOpenHelper.getmInstance(this);
        SQLiteDatabase db = helper.getWritableDatabase();
 
        if(db.isOpen()){
            String sql = "insert into persons(name) values('haha')";
            db.execSQL(sql);
            db.close();
        }
    }
 
    public void update(View view) {
        SQLiteOpenHelper helper = MySqliteOpenHelper.getmInstance(this);
        SQLiteDatabase db = helper.getWritableDatabase();
 
        if(db.isOpen()){
            String sql = "update persons set name=? where _id=?";
            db.execSQL(sql, new Object[]{"xixi", 2});
            db.close();
        }
    }
 
    public void delete(View view) {
        SQLiteOpenHelper helper = MySqliteOpenHelper.getmInstance(this);
        SQLiteDatabase db = helper.getWritableDatabase();
 
        if(db.isOpen()){
            String sql = "delete from persons where _id =?";
            db.execSQL(sql, new Object[]{3});
            db.close();
        }
    }
}

Room

  • 导入依赖：implementation 'androidx.room:room-runtime:2.2.5'
  • Student.java
package com.example.myroom;
 
import androidx.room.Entity;
import androidx.room.PrimaryKey;
 
@Entity
public class Student {
    // 主键唯一 自增id
    @PrimaryKey(autoGenerate = true)
    private int id;
 
    private String name;
 
    private int age;
 
    // 不需要id
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }
 
    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}
  • StudentDao.java
package com.example.myroom;
 
import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;
 
import java.util.List;
 
@Dao
public interface StudentDao {
    // 增
    @Insert
    void insertStudents(Student... students);
 
    // 改
    @Update
    void updateStudents(Student... students);
 
    // 条件删除
    @Delete
    void deleteStudents(Student... students);
 
    // 删除所有  @Delete单个条件删除
    @Query("DELETE FROM Student")
    void deleteAllStudents();
 
    // 查询所有
    @Query("SELECT * FROM Student ORDER BY ID DESC")
    List<Student> getAllStudent();
}
  • StudentDatabase.java
package com.example.myroom;
 
import android.content.Context;
 
import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;
 
@Database(entities = {Student.class}, version = 1, exportSchema = false)
public abstract class StudentDatabase extends RoomDatabase {
 
    // 用户只需要操作dao 必须暴露dao
    public abstract StudentDao getStudentDao();
 
    // 单例模式 反对db
    private static StudentDatabase INSTANCE;
    public static synchronized StudentDatabase getInstance(Context context){
        if(INSTANCE == null){
            INSTANCE = Room.databaseBuilder
                    (context.getApplicationContext(), StudentDatabase.class, "student_database")
                    // 默认异步线程
                    // 可以强制开启主线程使用
                    //.allowMainThreadQueries()
                    .build();
        }
        return INSTANCE;
    }
}
  • DBEngine.java
package com.example.myroom.manager;
 
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
 
import com.example.myroom.Student;
import com.example.myroom.StudentDao;
import com.example.myroom.StudentDatabase;
 
import java.util.List;
 
public class DBEngine {
    private StudentDao studentDao;
 
    public DBEngine(Context context){
        StudentDatabase studentDatabase = StudentDatabase.getInstance(context);
        studentDao = studentDatabase.getStudentDao();
    }
 
    // 对dao的增删改查
    // 插入
    public void insertStudents(Student... students){
        new InsertAsyncTask(studentDao).execute(students);
    }
 
    // 更新
    public void updateStudents(Student... students){
        new UpdateAsyncTask(studentDao).execute(students);
    }
 
    // 条件删除
    public void deleteStudents(Student... students){
        new DeleteAsyncTask(studentDao).execute(students);
    }
 
    // 全部删除
    public void deleteAllStudents(){
        new DeleteAllAsyncTask(studentDao).execute();
    }
    
    // 全部查询
    public void queryAllStudents(){
        new QueryAllAsyncTask(studentDao).execute();
    }
 
 
 
    // 异步操作
    // 插入
    static class InsertAsyncTask extends AsyncTask<Student, Void, Void>{
        private StudentDao dao;
 
        public InsertAsyncTask(StudentDao studentDao){
            dao = studentDao;
        }
 
        @Override
        protected Void doInBackground(Student... students) {
            dao.insertStudents(students);
            return null;
        }
    }
 
    // 更新
    static class UpdateAsyncTask extends AsyncTask<Student, Void, Void>{
        private StudentDao dao;
 
        public UpdateAsyncTask(StudentDao studentDao){
            dao = studentDao;
        }
 
        @Override
        protected Void doInBackground(Student... students) {
            dao.updateStudents(students);
            return null;
        }
    }
 
    // 条件删除
    static class DeleteAsyncTask extends AsyncTask<Student, Void, Void>{
        private StudentDao dao;
 
        public DeleteAsyncTask(StudentDao studentDao){
            dao = studentDao;
        }
 
        @Override
        protected Void doInBackground(Student... students) { // 条件删除
            dao.deleteStudents(students);
            return null;
        }
    }
 
    // 全部删除
    static class DeleteAllAsyncTask extends AsyncTask<Void, Void, Void>{
        private StudentDao dao;
 
        public DeleteAllAsyncTask(StudentDao studentDao){
            dao = studentDao;
        }
        
        @Override
        protected Void doInBackground(Void... voids) {
            dao.deleteAllStudents();
            return null;
        }
    }
 
    // 全部查询
    static class QueryAllAsyncTask extends AsyncTask<Void, Void, Void>{
        private StudentDao dao;
 
        public QueryAllAsyncTask(StudentDao studentDao){
            dao = studentDao;
        }
 
        @Override
        protected Void doInBackground(Void... voids) {
            List<Student> allStudent = dao.getAllStudent();
 
            for (Student student : allStudent) {
                Log.d("wmj", "doInBackground: " + student.toString());
            }
 
            return null;
        }
    }
 
}
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="插入"
        android:onClick="insertAction"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="修改"
        android:onClick="updateAction"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="删除"
        android:onClick="deleteAction"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="查询"
        android:onClick="queryAction"/>
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="全部删除"
        android:onClick="deleteAllAction"/>
 
</LinearLayout>
  • MainActivity.java
package com.example.myroom;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.view.View;
 
import com.example.myroom.manager.DBEngine;
 
public class MainActivity extends AppCompatActivity {
 
    private DBEngine dbEngine;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        dbEngine = new DBEngine(this);
    }
 
    // 插入
    public void insertAction(View view) {
        Student s1 = new Student("张三", 20);
        Student s2 = new Student("张四", 21);
        Student s3 = new Student("张五", 22);
        dbEngine.insertStudents(s1, s2, s3);
    }
 
    // 更新
    public void updateAction(View view) {
        Student s = new Student("王五", 30);
        s.setId(2);
        dbEngine.updateStudents(s);
    }
 
    // 条件删除
    public void deleteAction(View view) {
        Student student = new Student(null, 0);
        student.setId(2);
        dbEngine.deleteStudents(student);
    }
 
    // 全部查询
    public void queryAction(View view) {
        dbEngine.queryAllStudents();
    }
 
    // 全部删除
    public void deleteAllAction(View view) {
        dbEngine.deleteAllStudents();
    }
}

本文作者：n1ce2cv

本文链接：https://www.cnblogs.com/sprinining/p/15039323.html

版权声明：本作品采用知识共享署名-非商业性使用-禁止演绎 2.5 中国大陆许可协议进行许可。

posted @   n1ce2cv  阅读(100)  评论(0)  编辑  收藏  举报
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