如何从 SQL 数据库中选择所有记录并将其放入 Listview Android

Question

我正在尝试学习如何为 android 应用程序从数据库中存储和获取记录，我可以进行更新、插入、删除等操作，但是我在获取多条记录时遇到问题，我想问一下如何获取所有记录从 localhost phpmyadmin 中的表并使用共享首选项将结果导出到 android 应用程序中的列表视图中，这是我的 php 函数代码：

 public function getLessons($teacher) {

$sql = 'SELECT * FROM lessons WHERE teacher = :teacher';
$query = $this -> conn -> prepare($sql);
$query -> execute(array(':teacher' => $teacher));
$data = $query -> fetchObject();

$lesson["title"] = $data -> title; // im not sure if this is true
$lesson["maxstudent"] = $data -> maxstudent; // im not sure if this is true       
$lesson["about"] = $data -> about; // im not sure if this is true
return $lesson;// the result of sql query will be more than one record 
}

上面的代码将检索查询的结果，但我不确定代码，如果结果多于一条记录，教训的结果是什么？那是一个字符串数组吗？这是我在数据库代码中获取所有课程的 java 方法：

        private void getLessonProcess(String teacher){

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(Constants.BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        RequestInterface requestInterface = retrofit.create(RequestInterface.class);

        Lesson lesson = new Lesson();// its Java Class containing title,maxstudent and about
        lesson.setTeacher(teacher);// we set the teacher, so only specific teacher's lesson will be given as a result
        ServerRequest request = new ServerRequest();// server request is a class to connect to localhost
        request.setOperation(Constants.LESSONS);// constants.LESSONS is 'getlessons' the key that i use to trigger the SQL Query above
        request.setLesson(lesson);
        Call<ServerResponse> response = requestInterface.operation(request);

        response.enqueue(new Callback<ServerResponse>() {
            @Override
            public void onResponse(Call<ServerResponse> call, retrofit2.Response<ServerResponse> response) {

                ServerResponse resp = response.body();
                Snackbar.make(getView(), resp.getMessage(), Snackbar.LENGTH_LONG).show();


                  if(resp.getResult().equals(Constants.SUCCESS)){
                        SharedPreferences.Editor editor = pref.edit();
                        editor.putString(Constants.LESSONS,resp.getLesson().getLessontitle());
                        editor.putString(???,resp.getLesson().getMaxstudent());
                        editor.putString(???,resp.getLesson().getAbout());
                        ?????????? // What should i write here?
                        //in code above it will only put one record of the database and put it in shared preference 
                        editor.apply();
                    }
                }

                @Override
                public void onFailure(Call<ServerResponse> call, Throwable t) {

                    Log.d(Constants.TAG,"failed");
                    Snackbar.make(getView(), t.getLocalizedMessage(), Snackbar.LENGTH_LONG).show();                 

            }
        });
    }       

是否可以遍历所有数据并将其放入数组列表中，以便我可以使用适配器在 ListView 中显示结果？谢谢你

Answer 1

如果您的数据存储在数据库服务器（Mysql、oracle 等）中，您必须先用 Php 编写一个 Web 服务。该特定服务将从数据库中提取您的所有数据。然后，您必须编写一个 Web 逻辑，将提取的数据转换为 xml 或 json，因为只有这些格式的数据才能在网络中传输。如果您有多重数据，那么您也可以从该数据中创建 json 数组。 当android客户端通过Retrofit调用你的web服务时，它会自动在响应中获取json。那个json可以解析成java的ArrayList类。现在，您可以按照将列表数据填充到 ListView 中的基本步骤，在 ListView 中显示所有数据。

Answer 2

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub


    db.execSQL("CREATE TABLE " + TABLE_NAME
            + "(ID INTEGER PRIMARY KEY AUTOINCREMENT, " + key_msg + " STRING, " + key_isread + " STRING)");


}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

//*************************--------插入 GCM 消息---------* *************************//

public void insert_GCM_receive_data(String msg) {

    String value;
    SQLiteDatabase db = getWritableDatabase();

    ContentValues cv = new ContentValues();

    cv.put(key_msg, msg);
    cv.put(key_isread, "N");

    value = cv.toString();

    db.insert(TABLE_NAME, null, cv);
    System.out.println("/n******this is temp table name  " + TABLE_NAME + "\nthis is temp msg  " + cv + "\nmsg" + msg + "\nval" + value);

    db.close();

}

//--------------------------------------------- --------------------------------------------------//

//**********************----------获取警报数据---------- --******************************// 公共 ArrayList get_alert_msg() {

    ArrayList<String> name = new ArrayList<String>();
    try {
        SQLiteDatabase db = getWritableDatabase();
        Cursor c = null;
        c = db.rawQuery("SELECT  * FROM " + TABLE_NAME, null);

        System.out.println(c);

        for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {

            String str_id = c.getString(0);
            String str_msg = c.getString(1);
            String str_read = c.getString(2);
            Log.e("value", str_id + str_msg + str_read);

            HashMap<String, String> hm = new HashMap<String, String>();
            hm.put("msg", str_msg);
            hm.put("isread", str_read);


            name.add(str_msg);


        }
        c.close();
        db.close();

    } catch (Exception e) {
        Log.e("this not work", "" + e);
    }

    return name;
}`

//调用方法如

dbHelper = new Database_for_Received_data(this.getActivity()); name= new ArrayList(dbHelper.get_alert_msg());

使用“select * from table_name”之类的查询......然后在您的数据库类中扩展 SQLiteopenhelper。

它来自于使用数据存储、获取和操作目的..