Android 高手进阶教程(十三)之----Android 数据库SQLiteDatabase的使用！！

大家好，好久没有更新博客了，最近由于身体不适让大家久等了，好了，直接进入主题~

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：

由于代码都是现写，时间原因，没有全部加注释，如果大家 有什么不懂的地方，可以留言，我会尽快答复，如果需源代码，请留下你的Email

地址，ok,今天就到这里，大家晚安！