Content Provider--sharing data across programs

Content providers Content Provider

• The application's database is not allowed to be accessed by other apps
• The role of content providers is to let other apps access your database

• custom content provider, inherit the ContentProvider class , rewrite and delete the method ,

If you want to access the shared data in ContentProvider, you must use the Contentresolver class for CRUD operations

　　　　　　　Insert () Add Data Update () Updates data Delete () Remove data query () queries data

Getcontentresolver (). query (URI, projection, selection, Selectionargs, sortOrder);

Query () method parameters	corresponding SQL section	Describe
Uri	From table_name	Specify to query a table under an application
Projection	Select Column1, Column2	Specify the column name of the query
Selection	where column = value	Specify the WHERE constraint
Selectionargs	-	Provide a specific value for a placeholder in the where
By	Order by Column1, Column2	Specify how query results are sorted

• In the method to write additions and deletions to the database code, for example, add method

    @Override  public   uri insert (URI Uri, contentvalues Values) {Db.insert ( person, null  ,    values);  return   Uri;}   

• Define the label of the content provider in the manifest file, note that you must have the authorities attribute , which is the host name of the content provider, which functions like an address

  < Provider    
      android:name= "Com.example.contentprovider.PersonProvider"    android:authorities  = "Com.example.person"    android:exported= "true">
  </ 　　provider>

• Create a different app, access a custom content provider, implement an insert operation on the database

   Public void Click (View v) {    // Get the Content Decomposition object    contentresolver cr =  getcontentresolver ();     New  contentvalues();    CV.put("name", "Small square");    CV.put("Phone", 138856);    CV.put("money", +);     // URL: The host name    of the content provider Cr.Insert(uri.parse ("Content://com.example.person"), CV);}

Urimatcher

• Used to determine which match between a URI and a specified number of URIs

• Add a matching rule

  // Specify multiple URIUm.adduri ("Com.example.person", "person",Person_code), Um.adduri ("Com.example.person", " Company ", Company_code); // #号可以代表任意数字Um.adduri ("Com.example.person", "person/#", Query_one_person_code);

• Different tables can be implemented by URI-matching device

  @Override PublicURI insert(URI uri, contentvalues values) {if(Um.match (uri) = =Person_code) {Db.insert ("Person",NULL, values); }    Else if(Um.match (uri) = =Company_code) {Db.insert ("Company",NULL, values); }    Else{        Throw Newillegalargumentexception (); }    returnURI;}

• If the path has numbers, the API that pulls the numbers out

  ContentUris.parseId(uri);

SMS Database

• Only need to focus on SMS tables
• Just 4 fields to focus on
  • Body: SMS Content
  • Address: The sender or recipient number of the SMS (the buddy's number to chat with you)
  • Date: SMS Time
  • Type:1 for Receive, 2 for send

• read the system text message , the first query source to obtain the text message database content provider hostname and path, and then

  Contentresolver CR = getcontentresolver(); Cursor C= Cr.query ( Uri. Parse ("content://sms"),New string[]{"Body", "date", "Address", "type"},NULL,NULL,NULL); while(C.movetonext ()) {String body= c.getstring (0); String Date= c.getstring (1); String Address= C.getstring (2); String type= C.getstring (3); System.out.println (Body+ ";" + Date + ";" + address + ";" +type);}

• Insert System SMS

  Contentresolver cr =new  contentvalues () cv.put ("Body", "you tail number to the Bank of XXXX debit card received a transfer of RMB 1,000,000" ); Cv.put ("Address", 95555), Cv.put ("type", 1); Cv.put ("Date", System.currenttimemillis ()); Cr.insert (Uri.parse ("content://sms"), CV);

• Insert query system SMS requires registration permission

Contact database

• raw_contacts Table :
  • CONTACT_ID: Contact ID
• data Table : Contact details, one line
  • DATA1: Specific content of information
  • RAW_CONTACT_ID: Contact ID that describes which contact the information belongs to.
  • MIMETYPE_ID: Describe what type of information it belongs to
• mimetypes table : View specific types by mimetype_id to this table

Reading contacts

• Check the Raw_contacts table first to get the contact ID.

  Cursor cursor = cr.query(

　　　　　　　　　　　　new String[]{"contact_id"}, null, null, null);

• Then take the contact ID and go to the data table and query the information that belongs to the contact .

  Cursor c = cr.query(Uri.parse("content://com.android.contacts/data"),

　　　　　　　　　　　　new String[]{"data1", "mimetype"}, "raw_contact_id = ?", new String[]{contactId}, null);

• Gets the value of the Data1 field, which is the contact's information, What kind of information is judged by mimetype

   while   (C.movetonext ()) {String Data1  =    C.getstring (0 = c.getstring (1);  if  ("Vnd.android.cursor.item/email_v2" .equals (MimeType))    {Contact.setemail (data1);  else  if  ("    Vnd.android.cursor.item/name ".equals (MimeType)) {contact.setname (data1);  else  if  ("    Vnd.android.cursor.item/phone_v2 ".equals (MimeType)) {Contact.setphone (data1); }}

Insert Contact

• Query the Raw_contacts table first to determine how much the new contact ID should be

• Insert the identified contact ID into the raw_contacts table

  cv.put("contact_id", _id);cr.insert(Uri.parse("content://com.android.contacts/raw_contacts"), cv);

• Inserting data in the database table

  • Insert 3 fields: Data1, MimeType, raw_contact_id

    New contentvalues (), Cv.put ("Data1", "Zhao Liu"), Cv.put ("MimeType", "Vnd.android.cursor.item/name"); Cv.put ("raw_contact_id", _id); Cr.insert (Uri.parse ("Content://com.android.contacts/data"  ) New contentvalues (); Cv.put ("Data1", "1596874"); Cv.put ("MimeType", "Vnd.android.cursor.item/phone _v2 "), Cv.put (" raw_contact_id ", _id); Cr.insert(Uri.parse (" content://com.android.contacts/ Data "), CV);

Content Viewer

• When the database data changes, the content provider notifies you that a content watcher is registered on the content provider's URI to receive notification of changes to the data

  Cr.Registercontentobserver(Uri.parse ("Content://sms"),true,NewMyobserver (NewHandler ()));classMyobserverextends contentobserver{ Publicmyobserver (Handler Handler) {Super(handler); //TODO auto-generated Constructor stub    }    //This method is called when the content watcher receives a notification that the database has changed@Override Public void OnChange(BooleanSelfchange) {    }}

• Code to send notifications to content providers

  ContentResolver cr = getContext().getContentResolver();//发出通知，所有注册在这个uri上的内容观察者都可以收到通知cr.notifyChange(uri, null);

Content Provider--sharing data across programs