使用事务操作SQLite数据库

在使用SQLite数据库时，有时会遇到异步操作，这时就需要使用SQLite数据库事务来处理问题了。

使用SQLiteDatabase的beginTransaction()方法可以开启一个事务，程序执行到endTransaction() 方法时会检查事务的标志是否为成功，如果程序执行到endTransaction()之前调用了setTransactionSuccessful() 方法设置事务的标志为成功则提交事务，如果没有调用setTransactionSuccessful() 方法则回滚事务。

public void payment() {
  // 如果要对数据进行更改，就调用此方法得到用于操作数据库的实例,该方法以读和写方式打开数据库
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  // 开启事务
  db.beginTransaction();
  try {
   db.execSQL("update person set amount=amount-10 where personid=?",
     new Object[] { 1 });
   db.execSQL("update person set amount=amount+10 where personid=?",
     new Object[] { 2 });
   // 设置事务标志为成功，当结束事务时就会提交事务
   db.setTransactionSuccessful();
  } finally {
   db.endTransaction();
  }
 }

/***********/

MainActivity.java的实现方法有两种操作SQLite数据库

（1）

<pre name="code" class="java">package cn.itcast.db;

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

import cn.itcast.domain.Person;
import cn.itcast.service.PersonService;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

public class MainActivity extends Activity {
    private PersonService personService;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        this.personService = new PersonService(this);
       
        ListView listView = (ListView) this.findViewById(R.id.listView);
    
        List<Person> persons = personService.getScrollData(0, 5);
        List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>();
        for(Person person : persons){
         HashMap<String, Object> item = new HashMap<String, Object>();
         item.put("id", person.getId());
         item.put("name", person.getName());
         item.put("amount", person.getAmount());
         data.add(item);
        }
        SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,
          new String[]{"id", "name", "amount"}, new int[]{R.id.id, R.id.name, R.id.amount});
        listView.setAdapter(adapter);
        
        listView.setOnItemClickListener(new OnItemClickListener() {
   @Override
   public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    ListView lView = (ListView)parent;
    HashMap<String, Object> item = (HashMap<String, Object>)lView.getItemAtPosition(position);
    Toast.makeText(MainActivity.this, item.get("id").toString(), 1).show();
   }
  });

（2）

package cn.itcast.db;

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

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import cn.itcast.domain.Person;
import cn.itcast.service.CopyOfPersonService;

public class MainActivity extends Activity {

 private CopyOfPersonService copyOfPersonService;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  this.copyOfPersonService = new CopyOfPersonService(this);
  ListView listView = (ListView) this.findViewById(R.id.listView);

  Cursor cursor = copyOfPersonService.CopyOfgetCursorScrollData(0, 5);
  SimpleCursorAdapter adapter = new SimpleCursorAdapter(
    MainActivity.this, R.layout.item, cursor, new String[] { "_id",
      "name", "amount" }, new int[] { R.id.id, R.id.name,
      R.id.amount });
  listView.setAdapter(adapter);
         listView.setOnItemClickListener(new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
     ListView listView = (ListView)parent;
     Cursor data = (Cursor)listView.getItemAtPosition(position);
     int personid = data.getInt(data.getColumnIndex("_id"));
     Toast.makeText(MainActivity.this, personid+"", 1).show();
    }
   });

/*****/注意：

在使用SimpleCursorAdapter显示SQLite数据库时，必须注意SQLite数据表的主键名，由于SimpleCursorAdapter的方法只识别"_id"。所以，当用到SQLite的SimpleCursorAdapter时，就必须把数据表的主键命名为"_id"。否则，就会出现“ java.lang.IllegalArgumentException:column'_id' does not exist ”的异常。

显示的结果：

在调用payment（）方法之后，就会实现事务的操作。之后显示的结果：会对第一条记录的amount-10，第二条记录的amount+10操作。

在调用payment（）方法，我使用的是Android JUnit Test来测试的。

代码： http://download.csdn.net/detail/u012301841/7609897