Android的ContentProvider之三 监听ContentProvider数据改变

监听ContentProvider并随着ContentProvider的数据的改变而提供响应，这时就要利用ContentObserver

之前所涉及的ContentProvider实现insert、delete、update任意方法时，程序都会调用如下代码

getContext().getContentResolver().notifyChange(uri, null);

这行代码可用于通知所有注册在该Uri上的监听者：该ContentProvider所共享的数据发生了改变

监听ContentProvider数据改变的监听器需要继承ContentObserver类，并重写onChange(boolean selfChange)，CP数据发生改变时，onChange将被触发

注册监听器的方法如下：

registerContentObserver(Uri uri, boolean notifyForDescendents, ContentObserver observer),参数

• uri
• notifyForDescendents：若设为true，假如注册监听的Uri为content://abc，那么Uri为content://abc/xyz、content://abc/xyz/foo的数据改变时也会触发该监听器；若设为false，则只响应abc
• observer：监听器实例

getContentResolver().registerContentObserver(Uri.parse(“content://sms”),true, new SmsObserver(new Handler()));

上面代码中SmsObserver就是ContentObserver的子类

实例代码

publicclassMonitorSmsextendsActionBarActivity{

   @Override
   protectedvoidonCreate(BundlesavedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       getContentResolver().registerContentObserver(
       Uri.parse("content://sms"),true,
       newSmsObserver(newHandler()));
    }
   privatefinalclassSmsObserverextendsContentObserver
    {
   publicSmsObserver(Handlerhandler)
    {
   super(handler);
    }
   publicvoidonChange(booleanselfChange)
    {
   Cursorcursor= getContentResolver().query(
   Uri.parse("content://sms/outbox"),
   null,null,null,null);
   while(cursor.moveToNext())
    {
   StringBuildersb=newStringBuilder();
   sb.append("address=").append(cursor
    .getString(cursor.getColumnIndex("address")));
   sb.append(";subject=").append(cursor
    .getString(cursor.getColumnIndex("subject")));
   sb.append(";body=").append(cursor
    .getString(cursor.getColumnIndex("body")));
   sb.append(";time=").append(cursor
    .getString(cursor.getColumnIndex("date")));
   System.out.println("Has sent SMS::" + sb.toString());
   
    }
    }

    }

}