实例教程十：监听ContentProvider中数据的变化

不错的帖子：

Android漂亮蘑菇街UI界面
http://www.eoeandroid.com/thread-211482-1-1.html

Android 3D 乡村赛车 完整代码
http://www.eoeandroid.com/thread-211471-1-1.html

乐看播放器源代码，对写视频播放的人来说非常有用
http://www.eoeandroid.com/thread-211494-1-1.html

--------------------------------帖子正文---------------------

1.首先新建一个Aapp应用程序，还是需要使用到上一章的数据

package cn.itcast.app;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {
/**
* 监听ContentProvider(内容提供者)中的数据变化
* 为什么要监听？
* 例：此时有A应用和B应用，A应用向ContentProvider添加一条数据
* 而此时B应用若想知道A应用做了什么操作，则需ContentProvider通知
* ContentProvider会发出数据变化通知，B应用听过监听ContentProvider得到通知
*/

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}

public void insert(View v){
Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");
ContentResolver resolver = this.getContentResolver();
ContentValues values = new ContentValues();
values.put("name", "lixiao");
values.put("phone", "123456789");
values.put("amount", "500");
resolver.insert(uri, values);
}

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="insert"
android:text="@string/button" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>

<string name="hello">Hello World, MainActivity!</string>
<string name="app_name">A应用</string>
<string name="button">往内容提供者添加数据</string>

</resources>

使用上章的Other程序作用B应用程序，监听ContentProvider

package cn.itcast.other;

import android.app.Activity;

import android.content.ContentResolver;

import android.content.Context;

import android.database.Cursor;

import android.net.Uri;

import android.os.Bundle;

import android.os.Handler;

import android.util.Log;

import android.widget.Toast;

public class MainActivity extends Activity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");

//注册一个数据变化监听器

this.getContentResolver().registerContentObserver(uri, true, new PersonContentObserver(new Handler()));

}

private class PersonContentObserver extends ContentResolver{

public PersonContentObserver(Handler handler) {

super(handler);

}

public void onChange(boolean selfChange) {

// TODO Auto-generated method stub

Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");

Cursor cursor = getContentResolver().query(uri, null, null, null, "personId desc limit 1");

if(cursor.moveToFirst()){

String name = cursor.getString(cursor.getColumnIndex("name"));

Log.i("MainActivity", name);

}

}
}

}