Android 高手进阶教程(十三)之----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;第三种就是数据库SQLiteDatabase 存储。

文件存储我就不用多说了，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(七)之----Android 中Preferences的使用!

今天我们将讲一下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>  
      <EditText    
      android:id="@+id/author"   
      android:layout_width="fill_parent"   
      android:layout_height="wrap_content"   
      >  
      </EditText>  
      <ListView   
      android:id="@+id/bookslist"   
      android:layout_width="fill_parent"   
      android:layout_height="wrap_content"  
      >  
      </ListView>     
</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：