如何在 android studio 的列表中显示 sqlite 实体

Question

我是 android 的新人。我只是编写了一个应用程序，它从 EditText 中提供一个字符串并将其保存在 SQLite 中。知道我想在 ListView 中查看数据库的内容。但是我不知道你怎么能帮我写一个方法来完成这项工作。

那是我的 DBManager class

package com.sara.app.savetextapp;

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

public class DBManager extends SQLiteOpenHelper {

    public static final String DB_NAME = "Data";
    public static final String TABLE_NAME = "test";
    public static final String COLUMN_NAME= "text";
    private static final String COLUMN_TEXT_ID = "_id";

    public DBManager(Context context) {
        super(context, DB_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_NAME + " ("
            + COLUMN_TEXT_ID + " integer primary key autoincrement, "
            + COLUMN_NAME + " varchar(100))");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL("DROP TABLE IF EXISTS");
        onCreate(db);
    }

    public Cursor getDetails()
    {
        SQLiteDatabase db = getReadableDatabase();
        return db.rawQuery("select text from Data", null);
    }


}

Answer 1

应该是 "select text from test" 因为你的 table 名字叫 test。获得游标后，遍历它以读取数据。How to retrieve data from cursor class showing data in ListView use SimpleCursorAdapter - http://developer.android.com/reference/android/widget/SimpleCursorAdapter.html as suggested in comment. To improve code, instead of harcoding and using raw query try using projections - http://developer.android.com/training/basics/data-storage/databases.html

Answer 2

获取您要显示的列的字符串（将产品替换为您的列）。

public List<String> getAllContacts() {
        MyDBHandler helper = new MyDBHandler(getActivity().getApplicationContext(),null,null,1);
        List<String> contactList = new ArrayList<String>();
        // Select All Query
        String selectQuery = "SELECT  * FROM products WHERE 1";
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {

            do {

                Product contact = new Product();
                String c;
                c=(cursor.getString(1));

                // Adding contact name to list

                contactList.add(c);
            } while (cursor.moveToNext());
        }// return contact list
        cursor.close();
        db.close();
        return contactList;
    }

或者您可以使用 List 而不是 List（在我的例子中它将是 Product）：

public List<Product> getAllContacts() {
        MyDBHandler helper = new MyDBHandler(getActivity().getApplicationContext(),null,null,1);
        List<Product> contactList = new ArrayList<Product>();
        // Select All Query
        String selectQuery = "SELECT  * FROM products WHERE 1";
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {

            do {

                Product contact = new Product();
                String c;

                contact = new Product((cursor.getString(1)),cursor.getString(2) and so on)

                //From here you just fill your product

                contactList.add(contact);
            } while (cursor.moveToNext());
        }// return contact list
        cursor.close();
        db.close();
        return contactList;
    }

Answer 3

如果您正在编写笔记应用程序之类的东西并使用 SQLite 来存储它们，我在我的博客上就此主题写了一些相当冗长的文章 tutorials (Code | App) 可能会对您有所帮助.这是它的要点：

我建议您将 getDetails() 方法中的 rawQuery 替换为 query()。这是因为 SQL 语法是无情的，而 query() 方法会为您进行微调。

public Cursor getDetails() {
    return db.getReadableDatabase().query(TABLE_NAME, null, null, null, null, null, null); 
    //This will return all data in your table.
}

仅供参考，最好在 UI 线程之外进行查询，例如使用 AsyncTask，否则它们可能会导致应用程序冻结，甚至如果您的 table 特别大则崩溃.

关于将此数据分配给 ListView，最直接的方法是使用 SimpleCursorAdapter:

//Where "data" is the Cursor return by getDetails()
ListAdapter listAdapter = new SimpleCursorAdapter(this,
    R.layout.view_notes_row,
    data,
    new String[] {DBManager.COLUMN_NAME},
    new int[] {R.id.text_view},
    0);

为您的行定义一个 layout，并确保您的整体布局中有一个 ListView：

布局 - list_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/list_view" />
</FrameLayout>

行 - view_notes_row.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/text_view" />
</LinearLayout>

在你的 Activitiy 里面：

setContentView(R.layout.list_layout);
ListView listView = (ListView) findViewById(R.id.list_view);
listView.setAdapter(listAdapter);

如何在 android studio 的列表中显示 sqlite 实体

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