Question

我已经在SQLite中存储了书籍的详细信息。但是当我点击MainActivity中的按钮时，我不知道如何检索它。有人可以帮忙吗？还有如何在列表视图中显示它？这是Book.java

package com.hmkcode.android.model;

public class Book {

private int id;
private String title;
private String author;

public Book(){}

public Book(String title, String author) {
    super();
    this.title = title;
    this.author = author;
}

//getters & setters
// getting ID
public int getId(){
    return this.id;
}

// setting id
public void setId(int id){
    this.id = id;
}
// getting title
public String getTitle(){
    return this.title;
}

// setting title
public void setTitle(String title){
    this.title = title;
}
// getting author
public String getAuthor(){
    return this.author;
}

// setting author
public void setAuthor(String author){
    this.author = author;
}

}

这是MySQLiteHelper.java

package com.hmkcode.android.sqlite;

import java.util.LinkedList;
import java.util.List;

import com.hmkcode.android.model.Book;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;

public class MySQLiteHelper extends SQLiteOpenHelper {

// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "BookDB";

public MySQLiteHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);  
}

@Override
public void onCreate(SQLiteDatabase db) {
    // SQL statement to create book table
    String CREATE_BOOK_TABLE = "CREATE TABLE books ( " +
            "id INTEGER PRIMARY KEY AUTOINCREMENT, " + 
            "title TEXT, "+
            "author TEXT )";

    // create books table
    db.execSQL(CREATE_BOOK_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older books table if existed
    db.execSQL("DROP TABLE IF EXISTS books");

    // create fresh books table
    this.onCreate(db);
}
//---------------------------------------------------------------------

/**
 * CRUD operations (create "add", read "get", update, delete) book + get all books +  delete all books
 */

// Books table name
private static final String TABLE_BOOKS = "books";

// Books Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_AUTHOR = "author";

private static final String[] COLUMNS = {KEY_ID,KEY_TITLE,KEY_AUTHOR};

public void addBook(Book book){
    Log.d("addBook", book.toString());
    // 1. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();

    // 2. create ContentValues to add key "column"/value
    ContentValues values = new ContentValues();
    values.put(KEY_TITLE, book.getTitle()); // get title 
    values.put(KEY_AUTHOR, book.getAuthor()); // get author

    // 3. insert
    db.insert(TABLE_BOOKS, // table
            null, //nullColumnHack
            values); // key/value -> keys = column names/ values = column values

    // 4. close
    db.close(); 
}

public Book getBook(int id){

    // 1. get reference to readable DB
    SQLiteDatabase db = this.getReadableDatabase();

    // 2. build query
    Cursor cursor = 
            db.query(TABLE_BOOKS, // a. table
            COLUMNS, // b. column names
            " id = ?", // c. selections 
            new String[] { String.valueOf(id) }, // d. selections args
            null, // e. group by
            null, // f. having
            null, // g. order by
            null); // h. limit

    // 3. if we got results get the first one
    if (cursor != null)
        cursor.moveToFirst();

    // 4. build book object
    Book book = new Book();
    book.setId(Integer.parseInt(cursor.getString(0)));
    book.setTitle(cursor.getString(1));
    book.setAuthor(cursor.getString(2));

    Log.d("getBook("+id+")", book.toString());

    // 5. return book
    return book;
}

// Get All Books
public List<Book> getAllBooks() {
    List<Book> books = new LinkedList<Book>();

    // 1. build the query
    String query = "SELECT  * FROM " + TABLE_BOOKS;

    // 2. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(query, null);

    // 3. go over each row, build book and add it to list
    Book book = null;
    if (cursor.moveToFirst()) {
        do {
            book = new Book();
            book.setId(Integer.parseInt(cursor.getString(0)));
            book.setTitle(cursor.getString(1));
            book.setAuthor(cursor.getString(2));

            // Add book to books
            books.add(book);
        } while (cursor.moveToNext());
    }

    Log.d("getAllBooks()", books.toString());

    // return books
    return books;
}

 // Updating single book
public int updateBook(Book book) {

    // 1. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();

    // 2. create ContentValues to add key "column"/value
    ContentValues values = new ContentValues();
    values.put("title", book.getTitle()); // get title 
    values.put("author", book.getAuthor()); // get author

    // 3. updating row
    int i = db.update(TABLE_BOOKS, //table
            values, // column/value
            KEY_ID+" = ?", // selections
            new String[] { String.valueOf(book.getId()) }); //selection args

    // 4. close
    db.close();

    return i;

}

// Deleting single book
public void deleteBook(Book book) {

    // 1. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();

    // 2. delete
    db.delete(TABLE_BOOKS,
            KEY_ID+" = ?",
            new String[] { String.valueOf(book.getId()) });

    // 3. close
    db.close();

    Log.d("deleteBook", book.toString());

}
}

这是MainActivity.java

package com.hmkcode.android;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import java.util.List;
import com.hmkcode.android.model.Book;
import com.hmkcode.android.sqlite.MySQLiteHelper;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends Activity {
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteHelper db = new MySQLiteHelper(this); 
        /**
         * CRUD Operations
         * */
        // add Books
        Log.d("Inserting: ", "Inserting all Books..");
        db.addBook(new Book("Android Application Development Cookbook", "Wei Meng Lee"));   
        db.addBook(new Book("Android Programming: The Big Nerd Ranch Guide", "Bill Phillips and Brian Hardy"));       
        db.addBook(new Book("Learn Android App Development", "Wallace Jackson"));
       //Reading and getting all books
        Log.d("Reading: ", "Reading all Books.."); 
        List<Book> list = db.getAllBooks();
        for (Book cn:list) {
            String log = "Id: "+cn.getId()+" ,Title: " + cn.getTitle() + " ,Author: " + cn.getAuthor() ;
                // Writing Contacts to log
        Log.d("Name: ", log);
       // delete one book
       //db.deleteBook(list.get(0));

    }
  } 
}

Answer 1

你可以使用cursorAdapter在listview中显示它们，这里有一个很好的教程http://www.vogella.com/articles/AndroidSQLite/article.html

Answer 2

当您从SQLite读取数据时，一旦操作完成，关闭Cursor非常重要。
添加列表视图的步骤。

您缺少在oncreate方法中使用适配器。

其他一切，我认为你是对的。

将res / layout文件夹中的main.xml布局文件更改为以下内容。布局有一个ListView，用于显示现有的书籍。

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

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

</LinearLayout>

修改活动类。（扩展列表活动而不是活动）

public class MainActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    MySQLiteHelper db = new MySQLiteHelper(this); 
    /**
     * CRUD Operations
     * */
    // add Books
    Log.d("Inserting: ", "Inserting all Books..");
    db.addBook(new Book("Android Application Development Cookbook", "Wei Meng Lee"));   
    db.addBook(new Book("Android Programming: The Big Nerd Ranch Guide", "Bill Phillips and Brian Hardy"));       
    db.addBook(new Book("Learn Android App Development", "Wallace Jackson"));
   //Reading and getting all books
    Log.d("Reading: ", "Reading all Books.."); 
    List<Book> list = db.getAllBooks();
 ArrayAdapter<Book> adapter = new ArrayAdapter<Book>(this,
    android.R.layout.simple_list_item_1, values);
setListAdapter(adapter); 
    for (Book cn:list) {
        String log = "Id: "+cn.getId()+" ,Title: " + cn.getTitle() + " ,Author: " + cn.getAuthor() ;
            // Writing Contacts to log
    Log.d("Name: ", log);
   // delete one book
   //db.deleteBook(list.get(0));

}

} }

在res文件夹中添加名为simple_list_item_1的新文件。

按钮点击检索数据

2 个答案: