Question

Android中的ContentObserver问题

为什么这样注册getContentResolver().registerContentObserver(
Uri.parse("content://sms")
,true, new MySmsObserver(new Handler()));可以监听到有新信息，而这样
getContentResolver().registerContentObserver(
Uri.parse("content://sms/inbox")
,true, new SmsObserver(new Handler()));
却不行？我只是把Uri写的更具体了，是不是这个参数格式固定为"content://XXX",其中xxx为某个ContentProvider的名字，不能有子目录？真的是这样的话这个参数后面的true或者false有什么作用？

Answer 1

项目需求：
1 当联系人更新时，本地表可以获取到更新的通知
2 程序退出后，仍然可以更新

搜了网上很多文章，发现可以使用ContentObserver这个类实现需求1，对于需求2，当然是用Service实现了。
代码如下：

[java] view plaincopyprint?
public class DBUpdateService extends Service {

protected static final int LOCALCONTACTS_SYNC = 1;

private final static int ELAPSE_TIME = 5000;// FIXME: Should remind this
// time.

/*
* Set an observer to listen the LocalContacts' change. As the DB of contact
* would be change after make a call or send a message. We should listen the
* LogDB too.If it change, we believe the contact is not changed. It's not
* the best way,just is a temporary solution,but it can handle many cases.
*/
public ContentObserver mObserver = new ContentObserver(new Handler()) {

@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
Log.i(TAG, "Contact onChange");
mHandler.removeMessages(LOCALCONTACTS_SYNC);
Log.v(TAG, "removeMessages finish.");
mHandler.sendEmptyMessageDelayed(LOCALCONTACTS_SYNC, ELAPSE_TIME);
}
};

protected Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
Log.v(TAG, "++++handleMessage " + msg);
switch (msg.what) {
case LOCALCONTACTS_SYNC:
//do what you want to do
break;
default:
break;
}
}

};

@Override
public void onCreate() {
super.onCreate();

<span style="white-space: pre;"> </span>......

getContentResolver().registerContentObserver(
<strong>ContactsContract.Contacts.CONTENT_URI</strong>, true, mObserver);<strong>---------注册ContentObserver</strong>
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_STICKY;<strong>---------------这个可以使Service在需要运行时候自动运行，即使程序退出了</strong>
}

@Override
public void onDestroy() {
getContentResolver().unregisterContentObserver(mObserver);<span style="font-family: Arial,Helvetica,sans-serif;"><strong>-----------------------------------------------注销ContentObserver</strong></span>

}
}
public class DBUpdateService extends Service {

protected static final int LOCALCONTACTS_SYNC = 1;

private final static int ELAPSE_TIME = 5000;// FIXME: Should remind this
// time.

/*
* Set an observer to listen the LocalContacts' change. As the DB of contact
* would be change after make a call or send a message. We should listen the
* LogDB too.If it change, we believe the contact is not changed. It's not
* the best way,just is a temporary solution,but it can handle many cases.
*/
public ContentObserver mObserver = new ContentObserver(new Handler()) {

@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
Log.i(TAG, "Contact onChange");
mHandler.removeMessages(LOCALCONTACTS_SYNC);
Log.v(TAG, "removeMessages finish.");
mHandler.sendEmptyMessageDelayed(LOCALCONTACTS_SYNC, ELAPSE_TIME);
}
};

protected Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
Log.v(TAG, "++++handleMessage " + msg);
switch (msg.what) {
case LOCALCONTACTS_SYNC:
//do what you want to do
break;
default:
break;
}
}

};

@Override
public void onCreate() {
super.onCreate();

......

getContentResolver().registerContentObserver(
ContactsContract.Contacts.CONTENT_URI, true, mObserver);---------注册ContentObserver
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_STICKY;---------------这个可以使Service在需要运行时候自动运行，即使程序退出了
}

@Override
public void onDestroy() {
getContentResolver().unregisterContentObserver(mObserver);-----------------------------------------------注销ContentObserver

}
}

参考：

http://stackoverflow.com/questions/10173996/content-observer-onchange-method-called-twice-after-1-change-in-cursor?answertab=votes#tab-top

http://stackoverflow.com/questions/10431881/how-to-know-the-contact-is-updated-in-android/10432259#10432259

http://blog.csdn.net/luoshengyang/article/details/6985171

更新：
对于问题2，只需要注册了contentobserver就可以实现了，因为系统有一个ContentService会管理注册的observer。
如果有数据修改，系统会自动向注册的observer发送通知。
代码中需要实现两个onChange

Answer 2

Uri.parse("content://sms/inbox")

初略看了下，android中应该没有inbox这么一说的。sms是跟contract中的ID走的

追问

问题是
Cursor cursor = getContentResolver().query(
Uri.parse("content://sms/inbox")
, null, null, null, null);
while (cursor.moveToNext())
{。。。。。。。}
这样却可以查询到收件箱的内容

追答

监听和查找是一样的吗？

追问

那就是说只能监听sms而不能监听sms/inbox是吗，这样讲的话那个true就永远不能为false了吧，sms的组成部分应该不会变吧 会变的只是它的子目录inbox或者outbox什么的 如果为false不是永远都监听不到了 还是我理解错了 我觉得应该不是这样的 你能说的详细点吗？现在我监听的是"content://sms"，用模拟器测试发现重写的onChange()方法被调用了两次 应该是发送和接收信息各一次 我只想处理接收信息的事件 要怎么区分？