android:sqlite 数据库的事务详解

sqlite 数据库的事务详解，所有的解释都在代码中进行了注释

关于事务的应用主要都在MainActivity的onClickTransferAccountsSuccess和onClickTransferAccountsError方法中做的注释，请运行体会

运行结果如下图

1.布局文件activity_main.xml

2.ListView的item布局文件item_money.xml

3.activity的实现类MainActivity.java

package com.smartdot.transaction;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	private static final String TAG = "MainActivity";
	private OpenHelper helper;
	private ListView lv_many;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		helper = new OpenHelper(this);
		lv_many = (ListView) findViewById(R.id.lv_many);
		setBaseAdapter();//读取数据库的数据，并设置lv_many列表的数据
	}
	
	/**
	 * 正确的转账方法
	 */
	public void onClickTransferAccountsSuccess(View v) {
		SQLiteDatabase db = helper.getWritableDatabase();
		db.beginTransaction();//开启事务
		try {
			//马汉缺钱要王超给他转账100元	
			db.execSQL("update user set money=money-100 where name=? and money>=100",new String[]{"王朝"});
			db.execSQL("update user set money=money+100 where name=? and (select money from user u where u.name=?)>=100",new String[]{"马汉","王朝"});
			db.setTransactionSuccessful();//事务正确结束，如果此方法不执行，则所有的数据增删改操作都会回滚
			Toast.makeText(MainActivity.this, "转账成功！", Toast.LENGTH_SHORT).show();
			Log.i(TAG, "转账成功！");
		} catch (Exception e){
			Toast.makeText(MainActivity.this, "服务器忙，请稍后！", Toast.LENGTH_SHORT).show();
			Log.e(TAG, "服务器忙，请稍后！");
		} finally {
			db.endTransaction();//关闭事务
			setBaseAdapter();
		}
	}
	
	
	/**
	 * 错误的转账方法
	 */
	public void onClickTransferAccountsError(View v) {
		SQLiteDatabase db = helper.getWritableDatabase();
		db.beginTransaction();//开启事务
		try {
			//马汉缺钱要给他王超转账100元	
			db.execSQL("update user set money=money-100 where name=?",new String[]{"王朝"});
			int i = 10/0;//故意设置一个异常
			db.execSQL("update user set money=money+100 where name=?",new String[]{"马汉"});
			db.setTransactionSuccessful();//事务正确结束，如果此方法不执行，则所有的数据增删改操作都会回滚
			Toast.makeText(MainActivity.this, "转账成功！", Toast.LENGTH_SHORT).show();//此处永远不会执行
		} catch (Exception e){
			Toast.makeText(MainActivity.this, "服务器忙，请稍后！", Toast.LENGTH_SHORT).show();
			Log.e(TAG, "服务器忙，请稍后！");//真正企业开发，一般会报服务器忙，请稍后。不会抛出异常给用户！！！
		} finally {
			db.endTransaction();//关闭事务
			setBaseAdapter();
		}
	}
	
	/**
	 * 重新设置列表的适配器
	 */
	public void setBaseAdapter() {
		List> list = query();//转完账查询记录
		MyBaseAdapter mBaseAdapter = new MyBaseAdapter(list);//设置listView的适配器
		lv_many.setAdapter(mBaseAdapter);
	}
	
	/**
	 * 查询记录
	 * @return
	 */
	public List> query() {
		SQLiteDatabase db = helper.getWritableDatabase();
		Cursor cursor = db.query("user", new String[]{"name","money","age","phone","_id"}, null, null, null, null, null);
		List> list = new ArrayList>();
		Map map;
		while(cursor.moveToNext()) {
			map = new HashMap();
			map.put("name", cursor.getString(0));
			map.put("money", cursor.getString(1));
			map.put("age", cursor.getInt(2) + "");
			map.put("phone", cursor.getString(3));
			map.put("id", cursor.getInt(4) + "");
			list.add(map);
		}
		return list;
	}

	
	class MyBaseAdapter extends BaseAdapter {

		public List> list ;
		public MyBaseAdapter() {
		}
		public MyBaseAdapter(List> list) {
			this.list = list;
		}
		
		@Override
		public int getCount() {
			return list == null?0:list.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return list == null?null:list.get(position);
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		/**
		 * 通过适配器把数值填充到ListView中
		 */
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			ConvertViewTag tag ;//用于缓存内部的find的对象
			TextView tv_id = null;
			TextView tv_name = null;
			TextView tv_age = null;
			TextView tv_phone = null;
			TextView tv_money = null;
			if(convertView == null) {
				convertView = View.inflate(MainActivity.this, R.layout.item_money,null);
				tv_id = (TextView) convertView.findViewById(R.id.tv_id);
				tv_name = (TextView) convertView.findViewById(R.id.tv_name);
				tv_money = (TextView) convertView.findViewById(R.id.tv_money);
				tv_age = (TextView) convertView.findViewById(R.id.tv_age);
				tv_phone = (TextView) convertView.findViewById(R.id.tv_phone);
				
				tag = new ConvertViewTag();
				tag.tv_id = tv_id;
				tag.tv_money = tv_money;
				tag.tv_age = tv_age;
				tag.tv_name = tv_name;
				tag.tv_phone = tv_phone;
				
				convertView.setTag(tag);//缓存获得的View对象，如果数据多的时候避免二次创建
				
			} else {
				tag = (ConvertViewTag) convertView.getTag();//获取缓存的对象
				tv_id = tag.tv_id;
				tv_name = tag.tv_name;
				tv_money = tag.tv_money;
				tv_age = tag.tv_age;
				tv_phone = tag.tv_phone;
			}
			
			Map map = list.get(position);
			tv_id.setText(map.get("id"));
			tv_name.setText(map.get("name"));
			tv_money.setText(map.get("money"));
			tv_age.setText(map.get("age"));
			tv_phone.setText(map.get("phone"));
			
			
			return convertView;
		}
		class ConvertViewTag {
			public TextView tv_id;
			public TextView tv_name;
			public TextView tv_money;
			public TextView tv_age;
			public TextView tv_phone;
		}
	}

}

4.SQLiteOpenHelper的实现类OpenHelper.java

package com.smartdot.transaction;

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

/**
 * 实现android提供的抽象类SQLiteOpenHelper，用于sqlite数据库的操作
 * 
 * @author wangguang
 * 
 */
public class OpenHelper extends SQLiteOpenHelper {

	/**
	 * 第一次调用数据库，对出具库进行访问。
	 * 
	 * @param context
	 */
	public OpenHelper(Context context) {
		// 数据版本version只能比之前高，不得低于之前设定的版本号
		super(context, "transaction.db", null, 1);// 系统创建数据库
	}

	/**
	 * 当数据库（表）发生改变时可调用此方法
	 * 
	 * @param Context
	 *            context 上下文
	 * @param int version 数据库版本
	 */
	public OpenHelper(Context context, int version) {
		// 数据版本version只能比之前高，不得低于之前设定的版本号
		super(context, "smartdot.db", null, version);
	}

	/**
	 * 当数据库第一次创建的时候创建

	 * 这个表特别适合做创建表的操作
	 */
	@Override
	public void onCreate(SQLiteDatabase db) {
		String creatTable = "create table user (_id integer PRIMARY KEY AUTOINCREMENT NOT NULL,name varchar,money varchar(20),phone varchar,age int,sex int)";
		db.execSQL(creatTable);
		db.execSQL(
				"INSERT INTO USER (NAME,money,PHONE,SEX,AGE) VALUES(?,?,?,?,?)",
				new Object[] { "王朝", "100000", "18701545309", 1, 30 });// 添加测试数据
		db.execSQL(
				"INSERT INTO USER (NAME,money,PHONE,SEX,AGE) VALUES(?,?,?,?,?)",
				new Object[] { "马汉", "1000", "18701545309", 1, 30 });// 添加测试数据

	}

	/**
	 * 当数据库版本发生改变的时候调用此方法，此方法适合修改数据库的处理修改表，添加表，删除表

	 * 
	 * @param SQLiteDatabase
	 *            db

	 * @param int oldVersion 老版本号

	 * @param int newVersion 新版本号

	 */
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

	}

}