11.Android数据库SQLiteDatabase的使用

Android提供了三种数据存储方式：
第一种是文件存储。
第二种是SharedPreferences存储。
第三种是数据库SQLiteDatabase存储。

文件存储我就不多说了，而SharedPreferences可以存取简单的数据(int,double,float.etc)，它经常用于数据缓存，因为它读取存储简单。详细可以参见本系列《Android高手进阶教程》7.Android Preferences的使用

今天我们将讲一下Android SQLiteDatabase的使用。而掌握SqliteDatabase，将会我们接下来掌握ContentProvider打下良好的基石。

为了让大家更好的掌握，我们手把手完成该节的Demo。

第一步：新建一个Android工程，命名为SQLiteDatabaseDemo

第二步:创建一个新的类BooksDB.java这个类要继承于android.database.sqlite.SQLiteOpenHelper抽象类，我们要实现其中两个方法：onCreate(),onUpdate。具体代码如下：

package com.android.tutor;

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

public class BooksDB extends SQLiteOpenHelper {
    private final static String DATABASE_NAME = "BOOKS.db" ;
    private final static int DATABASE_VERSION = 1 ;
    private final static String TABLE_NAME = "books_table" ;
    public final static String BOOK_ID = "book_id" ;
    public final static String BOOK_NAME = "book_name" ;
    public final static String BOOK_AUTHOR = "book_author" ;

    public BooksDB(Context context) {
        // TODO Auto-generated constructor stub
        super (context, DATABASE_NAME, null , DATABASE_VERSION);
    }

    // 创建table
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE " + TABLE_NAME + " (" + BOOK_ID
                + " INTEGER primary key autoincrement, " + BOOK_NAME
                + " text, " + BOOK_AUTHOR + " text);" ;
        db.execSQL(sql);
    }

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

    public Cursor select() {
        SQLiteDatabase db = this .getReadableDatabase();
        Cursor cursor = db
                .query(TABLE_NAME, null , null , null , null , null , null );
        return cursor;
    }

    // 增加操作
    public long insert(String bookname, String author) {
        SQLiteDatabase db = this .getWritableDatabase();
        /* ContentValues */
        ContentValues cv = new ContentValues();
        cv.put(BOOK_NAME, bookname);
        cv.put(BOOK_AUTHOR, author);
        long row = db.insert(TABLE_NAME, null , cv);
        return row;
    }

    // 删除操作
    public void delete( int id) {
        SQLiteDatabase db = this .getWritableDatabase();
        String where = BOOK_ID + " = ?" ;
        String[] whereValue = { Integer.toString(id) };
        db.delete(TABLE_NAME, where, whereValue);
    }

    // 修改操作
    public void update( int id, String bookname, String author) {
        SQLiteDatabase db = this .getWritableDatabase();
        String where = BOOK_ID + " = ?" ;
        String[] whereValue = { Integer.toString(id) };

        ContentValues cv = new ContentValues();
        cv.put(BOOK_NAME, bookname);
        cv.put(BOOK_AUTHOR, author);
        db.update(TABLE_NAME, cv, where, whereValue);
    }
}

第三步:修改main.xml布局如下，由两个EditText和一个ListView组成，代码如下：

<? xml version = "1.0" encoding = "utf-8" ?>
< LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
    android:orientation = "vertical"
    android:layout_width = "fill_parent"
    android:layout_height = "fill_parent" >
    < EditText
        android:id = "@+id/bookname"
        android:layout_width = "fill_parent"
        android:layout_height = "wrap_content"
        />
    < EditText
        android:id = "@+id/author"
        android:layout_width = "fill_parent"
        android:layout_height = "wrap_content"
        />
    < ListView
        android:id = "@+id/bookslist"
        android:layout_width = "fill_parent"
        android:layout_height = "wrap_content"
        />
</ LinearLayout >

第四步:修改SQLiteDatabaseDemo.java代码如下：

package com.android.tutor;

import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class SQLiteDatabaseDemo extends Activity implements
        AdapterView.OnItemClickListener {
    private BooksDB mBooksDB;
    private Cursor mCursor;
    private EditText BookName;
    private EditText BookAuthor;
    private ListView BooksList;

    private int BOOK_ID = 0 ;
    protected final static int MENU_ADD = Menu.FIRST;
    protected final static int MENU_DELETE = Menu.FIRST + 1 ;
    protected final static int MENU_UPDATE = Menu.FIRST + 2 ;

    public void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout.main);
        setUpViews();
    }

    public void setUpViews() {
        mBooksDB = new BooksDB( this );
        mCursor = mBooksDB.select();

        BookName = (EditText) findViewById(R.id.bookname);
        BookAuthor = (EditText) findViewById(R.id.author);
        BooksList = (ListView) findViewById(R.id.bookslist);

        BooksList.setAdapter( new BooksListAdapter( this , mCursor));
        BooksList.setOnItemClickListener( this );
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super .onCreateOptionsMenu(menu);

        menu.add(Menu.NONE, MENU_ADD, 0 , "ADD" );
        menu.add(Menu.NONE, MENU_DELETE, 0 , "DELETE" );
        menu.add(Menu.NONE, MENU_DELETE, 0 , "UPDATE" );
        return true ;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        super .onOptionsItemSelected(item);
        switch (item.getItemId()) {
        case MENU_ADD:
            add();
            break ;
        case MENU_DELETE:
            delete();
            break ;
        case MENU_UPDATE:
            update();
            break ;
        }
        return true ;
    }

    public void add() {
        String bookname = BookName.getText().toString();
        String author = BookAuthor.getText().toString();
        // 书名和作者都不能为空，或者退出
        if (bookname.equals( "" ) || author.equals( "" )) {
            return ;
        }
        mBooksDB.insert(bookname, author);
        mCursor.requery();
        BooksList.invalidateViews();
        BookName.setText( "" );
        BookAuthor.setText( "" );
        Toast.makeText( this , "Add Successed!" , Toast.LENGTH_SHORT).show();
    }

    public void delete() {
        if (BOOK_ID == 0 ) {
            return ;
        }
        mBooksDB.delete(BOOK_ID);
        mCursor.requery();
        BooksList.invalidateViews();
        BookName.setText( "" );
        BookAuthor.setText( "" );
        Toast.makeText( this , "Delete Successed!" , Toast.LENGTH_SHORT).show();
    }

    public void update() {
        String bookname = BookName.getText().toString();
        String author = BookAuthor.getText().toString();
        // 书名和作者都不能为空，或者退出
        if (bookname.equals( "" ) || author.equals( "" )) {
            return ;
        }
        mBooksDB.update(BOOK_ID, bookname, author);
        mCursor.requery();
        BooksList.invalidateViews();
        BookName.setText( "" );
        BookAuthor.setText( "" );
        Toast.makeText( this , "Update Successed!" , Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onItemClick(AdapterView<!--?--> parent, View view, int position,
            long id) {

        mCursor.moveToPosition(position);
        BOOK_ID = mCursor.getInt( 0 );
        BookName.setText(mCursor.getString( 1 ));
        BookAuthor.setText(mCursor.getString( 2 ));

    }

    public class BooksListAdapter extends BaseAdapter {
        private Context mContext;
        private Cursor mCursor;

        public BooksListAdapter(Context context, Cursor cursor) {

            mContext = context;
            mCursor = cursor;
        }

        @Override
        public int getCount() {
            return mCursor.getCount();
        }

        @Override
        public Object getItem( int position) {
            return null ;
        }

        @Override
        public long getItemId( int position) {
            return 0 ;
        }

        @Override
        public View getView( int position, View convertView, ViewGroup parent) {
            TextView mTextView = new TextView(mContext);
            mCursor.moveToPosition(position);
            mTextView.setText(mCursor.getString( 1 ) + "___"
                    + mCursor.getString( 2 ));
            return mTextView;
        }

    }
}

第五步:运行程序效果如下：

第六步：查看我们所建的数据库。有两种方法：第一种用命令查看：adb shell ls data/data/com.android.tutor/databases。

另一种方法是用DDMS查看，在data/data下面对应的应用程序的包名 下会有如下数据库，如图所示：