Android之ContentObserver内容观察者的使用
转载:原博客地址:http://blog.csdn.net/jason0539/article/details/22581297
ContentObserver——内容观察者，目的是观察(捕捉)特定Uri引起的数据库的变化，继而做一些相应的处理，它类似于
数据库技术中的触发器(Trigger)，当ContentObserver所观察的Uri发生变化时，便会触发它。
（1）注册：
public final void registerContentObserver(Uri uri, boolean notifyForDescendents, ContentObserver observer)。 功能：为指定的Uri注册一个ContentObserver派生类实例，当给定的Uri发生改变时，回调该实例对象去处理。复制代码
（2）卸载： public final void unregisterContentObserver(ContentObserver observer)
功能：取消对给定Uri的观察复制代码
下面是一个监听收信箱的Demo
首先是一个监听类：
package jason.observer;import android.content.Context;import android.database.ContentObserver;import android.database.Cursor;import android.net.Uri;import android.os.Handler;public class SMSContentObserver extends ContentObserver { Context context; Handler handler; public SMSContentObserver(Context c, Handler handler) { super(handler); // TODO Auto-generated constructor stub this.context = c; this.handler = handler; } @Override public void onChange(boolean selfChange) { // TODO Auto-generated method stub super.onChange(selfChange); Uri outMMS = Uri.parse("content://sms/inbox"); //desc 降序 asc 升序 Cursor cursor = context.getContentResolver().query(outMMS, null, null, null, "date ASC"); if(cursor != null){ System.out.println("the number is " + cursor.getCount()); StringBuilder builder = new StringBuilder(); while(cursor.moveToNext()){ builder.append("发件人信息:" + cursor.getString(cursor.getColumnIndex("address"))); builder.append("信息内容："+cursor.getString(cursor.getColumnIndex("body"))+"\n"); } cursor.close(); String builder2 = builder.toString(); handler.obtainMessage(1, builder2).sendToTarget(); } }}复制代码 （2）注册监听类的activity
package jason.observer;import android.app.Activity;import android.net.Uri;import android.os.Bundle;import android.os.Handler;import android.widget.TextView;public class ObserverActivity extends Activity { SMSContentObserver contentObserver; TextView tv_number; TextView tv_content; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_observer); tv_content = (TextView) findViewById(R.id.tv_content); tv_number = (TextView) findViewById(R.id.tv_number); contentObserver = new SMSContentObserver(this, handler); Uri uri = Uri.parse("content://sms"); getContentResolver().registerContentObserver(uri, true, contentObserver); } Handler handler = new Handler() { public void handleMessage(android.os.Message msg) { switch (msg.what) { case 1: String sb = (String) msg.obj; tv_content.setText(sb); break; default: break; } }; };}复制代码 最后别忘记了加入 读取消息的权限