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

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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);                        }                }    }}

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