The application of the viewer mode in the shopping cart

The observer pattern is, for example, setting an observer for a adapter that executes the callback method in the observer when adapter calls the Notifydatasetchaged () method

1  PackageCom.xqx.adapterobserver;2 3 Importandroid.app.Activity;4 ImportAndroid.database.DataSetObserver;5 ImportAndroid.os.Bundle;6 ImportAndroid.view.View;7 Importandroid.widget.*;8 ImportOrg.w3c.dom.Text;9 Ten Importjava.util.ArrayList; One Importjava.util.List; A  -  Public classMainactivityextendsActivity { -     /** the * Called when the activity is first created. -      */ -  -     PrivateArrayadapter<integer>adapter; +     PrivateList<integer>list; -     PrivateListView ListView; +     PrivateTextView text; A  at     //Create observer -     PrivateDatasetobserver Sumobserver =NewDatasetobserver () { -         /** - * Called when Adapter's Notifydatasetchanged method executes -          */ - @Override in          Public voidonChanged () { -             Super. onChanged (); to             //perform the appropriate action +             intsum = 0; -              for(inti = 0; I < list.size (); i++) { thesum+=List.get (i); *             } $Text.settext ("Total Amount:" +sum);Panax Notoginseng         } -  the         /** + * Called when adapter calls the Notifydatasetinvalidate method execution A          */ the @Override +          Public voidoninvalidated () { -             Super. oninvalidated (); $             //perform the appropriate action $         } -     }; - @Override the      Public voidonCreate (Bundle savedinstancestate) { -         Super. OnCreate (savedinstancestate);Wuyi Setcontentview (r.layout.main); the  -List =NewArraylist<integer>(); Wu          for(inti = 0; I < 30; i++) { -List.add (0); About         } $adapter =NewArrayadapter<integer> ( This, Android. r.layout.simple_list_item_1,list); -         //Registered Observer - Adapter.registerdatasetobserver (sumobserver); -Text =(TextView) Findviewbyid (r.id.text); AListView =(ListView) Findviewbyid (R.id.listview); + Listview.setadapter (adapter); the  -Listview.setonitemclicklistener (NewAdapterview.onitemclicklistener () { $ @Override the              Public voidOnitemclick (adapterview<?> adapterview, view view,intILongl) { theList.set (i,2); the                 //changes the list item's 0 to the 2 update adapter, the adapter.notifydatasetchanged (); -                 //after the method is executed, the Datasetobserver Observer observes in             } the         }); the  About     } the  the @Override the     protected voidOnDestroy () { +         Super. OnDestroy (); -         //Logout Observer the Adapter.unregisterdatasetobserver (sumobserver);Bayi     } the } the  -Mainactivity.java

Activity

The application of the viewer mode in the shopping cart