android15

【监听ContentProvider中数据的变化】

如果ContentProvider的访问者需要知道ContentProvider中的数据发生变化，可以在ContentProvider 发生数据变化时调用getContentResolver().notifyChange(uri, null)来通知注册在此URI上的访问者，例子如下：
public class PersonContentProvider extends ContentProvider {
public Uri insert(Uri uri, ContentValues values) {
db.insert("person", "personid", values);
getContext().getContentResolver().notifyChange(uri, null);
}
}
如果ContentProvider的访问者需要得到数据变化通知，必须使用ContentObserver对数据（数据采用uri描述）进行监听，当监听到数据变化通知时，系统就会调用ContentObserver的onChange()方法：
getContentResolver().registerContentObserver(Uri.parse("content://cn.itcast.providers.personprovider/person"),
          true,//true表示只要发出通知的Uri以方法第一个参数开头都能被监听到，否侧监听uri必须与发出通知的uri完全匹配才能被监听到
                                           new PersonObserver(new Handler()));
public class PersonObserver extends ContentObserver{
public PersonObserver(Handler handler) {
  super(handler);
  }
public void onChange(boolean selfChange) {
     //此处可以进行相应的业务处理
}
}

 1 package cn.itcast.app;
 2 
 3 import android.app.Activity;
 4 import android.content.ContentResolver;
 5 import android.content.ContentValues;
 6 import android.net.Uri;
 7 import android.os.Bundle;
 8 import android.view.View;
 9 
10 public class MainActivity extends Activity {
11     /** Called when the activity is first created. */
12     @Override
13     public void onCreate(Bundle savedInstanceState) {
14         super.onCreate(savedInstanceState);
15         setContentView(R.layout.main);
16     }
17     
18     public void insert(View v){
19         Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");
20         ContentResolver resolver = this.getContentResolver();
21         ContentValues values = new ContentValues();
22         values.put("name", "A-App");
23         values.put("phone", "18607687688");
24         values.put("amount", "700000");
25         resolver.insert(uri, values);
26     }
27 }

View Code

 1 package cn.itcast.other;
 2 
 3 import android.app.Activity;
 4 import android.database.ContentObserver;
 5 import android.database.Cursor;
 6 import android.net.Uri;
 7 import android.os.Bundle;
 8 import android.os.Handler;
 9 import android.util.Log;
10 
11 public class MainActivity extends Activity {
12     /** Called when the activity is first created. */
13     @Override
14     public void onCreate(Bundle savedInstanceState) {
15         super.onCreate(savedInstanceState);
16         setContentView(R.layout.main);
17         Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");
18         this.getContentResolver().registerContentObserver(uri, true, new PersonContentObserver(new Handler()));
19     }
20     
21     private class PersonContentObserver extends ContentObserver{
22 
23         public PersonContentObserver(Handler handler) {
24             super(handler);
25         }
26 
27         @Override
28         public void onChange(boolean selfChange) {
29             // select * from person order by personid desc limit 1
30             Uri uri = Uri.parse("content://cn.itcast.providers.personprovider/person");
31             Cursor cursor = getContentResolver().query(uri, null, null, null, "personid desc limit 1");
32             if(cursor.moveToFirst()){
33                 String name = cursor.getString(cursor.getColumnIndex("name"));
34                 Log.i("MainActivity", name);
35             }
36         }
37         
38     }
39 }

View Code