Android之ContentObserver内容观察者的使用

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。
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(2)卸载: public final void unregisterContentObserver(ContentObserver observer)

  功能:取消对给定Uri的观察
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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();
		}
	}

}
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(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;
			}
		};	
	};

}
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最后别忘记了加入 读取消息的权限

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