Android contenobserver Monitor Contact data changes

First, Knowledge introduction

1. ContentProvider is the content provider

Contentresolver is the content resolver (manipulating the data provided by the content)

Contentobserver is a content observer (observing the data changes provided by the content provider)

2, Contentobserver need contentresolver to register.

Resolver.registercontentobserver (uri,true,observer);

①uri (first parameter): The URI of the listener listening on ContentProvider

②notifyfordescendents (second parameter): set to True. (If the requested URI is CONTENT://ABC, the URI is content://abc/xyz data changes will be detected.)

③observer: listener instance.

3, using the OnChange method in observer, when the data is changed, the callback method is automatically executed.

second, the project practice"Step"

① Defining observer listeners

② Get to contact Contentresolver

③ registered observer.

④ Important point: Add access rights (dynamic also)

⑤ Logoff Observer

"Project Structure"

　　　　

"Mainactivity"

Hint: This observer is written in the form of an inner class. The code has only this part, and the others do not need to be added.

1 ImportAndroid. Manifest;2 ImportAndroid.content.ContentResolver;3 ImportAndroid.content.pm.PackageManager;4 ImportAndroid.database.ContentObserver;5 ImportAndroid.net.Uri;6 ImportAndroid.os.Handler;7 Importandroid.provider.ContactsContract;8 ImportAndroid.support.v4.app.ActivityCompat;9 Importandroid.support.v7.app.AppCompatActivity;Ten ImportAndroid.os.Bundle; One ImportAndroid.util.Log; A ImportAndroid.widget.Toast; -  -  Public classMainactivityextendsappcompatactivity { the  -Contentresolver resolver =NULL; -Observer Observer =NULL; - @Override +     protected voidonCreate (Bundle savedinstancestate) { -         Super. OnCreate (savedinstancestate); + Setcontentview (r.layout.activity_main); A          at         //Dynamic permission requests (also ask for permission in the Androidmanifest file) -         if(Activitycompat.checkselfpermission ( This, -Manifest.permission.READ_CONTACTS)! = - packagemanager.permission_granted); - Activitycompat.requestpermissions ( -Mainactivity. This, in                         Newstring[]{Manifest.permission.READ_CONTACTS -},0); to                  +         //Instantiate Observer -Observer =NewObserver (NewHandler ()); the         //Get resolver *Resolver =getcontentresolver (); $Uri uri =ContactsContract.Contacts.CONTENT_URI;Panax Notoginseng         //Register Observer -Resolver.registercontentobserver (URI,true, observer); the  +     } A  the     classObserverextendscontentobserver{ +  -          PublicObserver (Handler Handler) { $             Super(handler); $         } -  - @Override the          Public voidOnChange (BooleanSelfchange) { -             Super. OnChange (selfchange);WuyiToast.maketext (mainactivity. This, the"Contact List has changed", Toast.length_short). Show (); -             //Add Toast in onchange method for easy observation Wu         } -     } About  $ @Override -      Public voidOndetachedfromwindow () { -         Super. Ondetachedfromwindow (); -         //unregister observer in activity A Resolver.unregistercontentobserver (Observer); +     } the}

"effect" has just deleted a contact information

　　　　

Summary

①contentobserver is able to detect data changes provided by ContentProvider in a timely manner.

②contentobserver can communicate not only with the system, but also from the programs that they create by contentobserver,contentresolver

Android contenobserver Monitor Contact data changes