android--creating your own content Provider

To implement cross-program shared data requires a content provider that provides access to other applications, and creates a new class to inherit ContentProvider to create a content provider of its own. There are 6 abstract methods in the ContentProvider class that need to be rewritten when using subclass inheritance.

1  Public classMyproviderextendsContentProvider {2 3 @Override4     /*5 called when initializing6 operations such as creating and upgrading the database are usually done here, and returning TRUE indicates success in initialization. 7 initialization occurs only if there is a contentresolver attempt to access data in the program. 8      */9      Public BooleanonCreate () {Ten         return false; One     } A  -     /* - Querying Data the URI determines which table is queried - projection query that column - selection and Selectionargs query those rows - SortOrder to sort results + The returned data is stored in the cursor object -      */ + @Override A      PublicCursor query (Uri uri, string[] projection, string selection, string[] Selectionargs, string sortOrder) { at         return NULL; -     } -  -     /* - returns the corresponding MIME type according to the data URI passed in -      */ in @Override -      PublicString getType (Uri uri) { to         return NULL; +     } -     /* the Add Data * The URI determines which table is added $ values Save the data you want to addPanax Notoginseng returns a URI that represents the new record -      */ the @Override +      Publicuri insert (URI uri, contentvalues values) { A         return NULL; the     } +     /* - Delete Data $ selection and Selectionargs delete those rows $ returns the number of rows that were deleted -      */ - @Override the      Public intDelete (Uri Uri, String selection, string[] selectionargs) { -         return0;Wuyi     } the     /* - Update existing Data Wu URI determines which table is updated - Values New Data About selection and Selectionargs update those lines $ returns the number of rows updated -      */ - @Override -      Public intupdate (URI Uri, contentvalues values, String selection, string[] selectionargs) { A         return0; +     } the  -}

A standard content URI notation is this:

Content://com.example.app.providder/table1

This means that you want to access the data in the Table1 table in the Com.example.app application

Content://com.example.app.providder/table1/1

This means that you want to access data with ID 1 in the Table1 table in the Com.example.app application.

content://com.example.app.providder/*

This means that you want to access any of the tables in this app Com.example.app

content://com.example.app.providder/table1/#

This means that you want to access data from any row in the Table1 table in the Com.example.app application.

where * represents any length of any character # represents any length of the number

Then use urimatcher this class to implement the function of matching content URI, there is a method of Adduri () in Urimatcher, 3 parameters, can be authority, path, and a custom code respectively, when calling Urimatcher's match ( method is to pass in a URI that returns a custom code that matches the URI.

The Modified code:

　　

1  Public classMyproviderextendsContentProvider {2 3     //custom code to identify the URI4      Public Static Final intTable1_dir = 0;5 6      Public Static Final intTable1_item = 1;7 8      Public Static Final intTable2_dir = 2;9 Ten      Public Static Final intTable2_item = 3; One  A     //Create an instance of Urimatcher -     Private StaticUrimatcher Urimatcher; -  the     //match the custom code with the desired URI -     Static { -Urimatcher =NewUrimatcher (urimatcher.no_match); -Urimatcher.adduri ("Xbt.exp11.provider", "table1", Table1_dir); +Urimatcher.adduri ("Xbt.exp11.provider", "table1/#", Table1_item); -Urimatcher.adduri ("Xbt.exp11.provider", "Table2", Table2_dir); +Urimatcher.adduri ("Xbt.exp11.provider", "table2/#", Table2_item); A  at     } -     ... -     /* - Querying Data - URI determines which table is queried - projection query that column in selection and Selectionargs query those rows - SortOrder to sort results to The returned data is stored in the cursor object +      */ - @Override the      PublicCursor query (Uri uri, string[] projection, string selection, string[] Selectionargs, string sortOrder) { *  $         //determine what data is expected to be accessedPanax Notoginseng         Switch(Urimatcher.match (URI)) { -              CaseTable1_dir: the                 //querying all data in a table1 table +                  Break; A              CaseTable1_item: the                 //querying a single piece of data in a table1 table +                  Break; -              CaseTable2_dir: $                 //querying all data in a table2 table $                  Break; -              CaseTable2_item: -                 //querying a single piece of data in a table2 table the                  Break; -             default:Wuyi                  Break; the         } -         ... Wu     } -  About     ... $  -}

Insert (), update (), delete () can also use switch (Urimatcher.match (URI)) {:} Such a judgment sentence to determine the desired access to the table, and then the corresponding operation

The GetType () method is a method that all content providers must provide to get the MIME type that the URI object corresponds to.

A content URI that corresponds to a MIME string consists mainly of 3 parts, and the android format specifies:

1. Must start with VND

2. If the content URI ends with a path, then android.cursor.dir/is followed, and if the content URI ends with an ID, then the android.cursor.item/is followed up

3, finally connected to the Vnd.<authority>.<path>

Therefore, for content://com.example.app.providder/table1 this content URI, its corresponding MIME type can be written as:

Vnd.android.cursor.dir/vnd.example.app.providder.table1

For CONTENT://COM.EXAMPLE.APP.PROVIDDER/TABLE1/1 This content URI, the MIME type it corresponds to can be written as:

Vnd.android.cursor. Item/vnd.example.app.providder.table1

The logic for implementing the GetType () method is as follows:

 Public classMyproviderextendsContentProvider {.../*returns the corresponding MIME type according to the data URI passed in*/@Override PublicString getType (Uri uri) {Switch(Urimatcher.match (URI)) { CaseTable1_dir:return"Vnd.android.cursor.dir/vnd.xbt.exp11.provider.table1";  CaseTable1_item:return"Vnd.android.cursor.item/vnd.xbt.exp11.provider.table1";  CaseTable2_dir:return"Vnd.android.cursor.dir/vnd.xbt.exp11.provider.table2";  CaseTable2_item:return"Vnd.android.cursor.item/vnd.xbt.exp11.provider.table2"; default:                 Break; }        return NULL; }}

android--creating your own content Provider