监测Databases的改变：ContentObserver与DatasetObserver

前面有一篇关于Databases的NotifyChange: http://aijiawang-126-com.iteye.com/blog/812004
其实这文章讲的就是通过ContentObserver来监测Databases的改变，并且做出相应的处理。
但对Databases的改变，除了可以通过ContentObserver来监测外，还可以通过DatasetObserver来监测。那我们来看看它们之间的区别

1，ContentObserver
Receives call backs for changes to content. Must be implemented by objects which are added to a ContentObservable.
接受回调去改变Content.
其实ContentObserver主要是通过Uri来监测特定的Databases的表：
比如：

public class TestContentObserver extends Activity {
	MyContentObserver mco;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mco=new MyContentObserver(new MyHandler());
        
        
    }
    @Override
    protected void onResume() {
    	// TODO Auto-generated method stub
    	super.onResume();
    getApplicationContext().getContentResolver().registerContentObserver(Contacts.CONTENT_URI, true, mco);
    }
    
    class MyHandler extends Handler{
    	@Override
    	public void handleMessage(Message msg) {
    		// TODO Auto-generated method stub
    		super.handleMessage(msg);
    	}
    };
    
    class MyContentObserver extends ContentObserver{

		public MyContentObserver(Handler handler) {
			super(handler);
			// TODO Auto-generated constructor stub
		}
		@Override
		public void onChange(boolean selfChange) {
			// TODO Auto-generated method stub
			super.onChange(selfChange);
			System.out.println("onChange "+selfChange);
		}
    	
		@Override
		public boolean deliverSelfNotifications() {
			// TODO Auto-generated method stub
			return super.deliverSelfNotifications();
			//return true;
		}
    };
}

registerContentObserver(Contacts.CONTENT_URI, true, mco);通过对Contacts.CONTENT_URI的监测，当Contacts发生变化就会call back回调mco里面的onChange方法来处理变化。

2，DatasetObserver
Receives call backs when a data set has been changed, or made invalid. The typically data sets that are observed are Cursors or Adapters. DataSetObserver must be implemented by objects which are added to a DataSetObservable.
DatasetObserver当数据集改变或者无效时，就会回调相应的函数做出处理，而典型的数据集就是cursor或者adapters.
这就是说通过cursor或者adapters的改变来做出相应的处理。
比如：QuickSearchBox中的SuggestionsAdapter

 mSuggestionsAdapter.registerDataSetObserver(new SuggestionsObserver()); private class SuggestionsObserver extends DataSetObserver {
        @Override
        public void onChanged() {
            updateInputMethodSuggestions();
        }
    }