Android中ContentProvider和ContentResolver使用入门

爱被打了一巴掌 2022-09-30 06:25 153阅读 0赞

在Android中，我们的应用有的时候需要对外提供数据接口，可以有如下几种方法：1）AIDL 2）Broadcast 3）ContentProvider。  
使用AIDL需要我们编写AIDL接口以及实现，而且对方也要有相应的接口描述，有点麻烦；使用Broadcast，我们不需要任何接口描述，只要协议文档就可以了，但是有点不好就是，这种方式不直接而且是异步的；使用ContentProvider我们不需要接口描述，只需要知道协议，同时这种方式是同步的，使用方便。下面是ContentProvider实现：

![ExpandedBlockStart.gif][] ![ContractedBlock.gif][] /\*\* \*/ /\*\*  
![InBlock.gif][] \*   
![ExpandedBlockEnd.gif][] \*/   
![None.gif][] package  com.backgroundservice;  
![None.gif][]  
![None.gif][] import  android.content.ContentProvider;  
![None.gif][] import  android.content.ContentValues;  
![None.gif][] import  android.content.UriMatcher;  
![None.gif][] import  android.database.Cursor;  
![None.gif][] import  android.database.sqlite.SQLiteDatabase;  
![None.gif][] import  android.database.sqlite.SQLiteQueryBuilder;  
![None.gif][] import  android.net.Uri;  
![None.gif][] import  android.util.Log;  
![None.gif][]  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] /\*\* \*/ /\*\*  
![InBlock.gif][] \* TODO  
![InBlock.gif][] \*   
![InBlock.gif][] \* @author tianlu  
![InBlock.gif][] \* @version 1.0 Create At : 2010-2-18 下午01:58:39  
![ExpandedBlockEnd.gif][] \*/   
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] public   class  TestContentProvider  extends  ContentProvider  ![dot.gif][] \{  
![InBlock.gif][]    private SQLiteDatabase mDb;  
![InBlock.gif][]    private DatabaseHelper mDbHelper = null;  
![InBlock.gif][]    private static final String DATABASE\_NAME = "rssitems.db";  
![InBlock.gif][]    private static final String DATABASE\_TABLE\_NAME = "rssItems";  
![InBlock.gif][]    private static final int DB\_VERSION = 1;  
![InBlock.gif][]    private static final int ALL\_MESSAGES = 1;  
![InBlock.gif][]    private static final int SPECIFIC\_MESSAGE = 2;  
![InBlock.gif][]  
![InBlock.gif][]    // Set up our URL matchers to help us determine what an  
![InBlock.gif][]    // incoming URI parameter is.  
![InBlock.gif][]    private static final UriMatcher URI\_MATCHER;  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    static ![dot.gif][]\{  
![InBlock.gif][]        URI\_MATCHER = new UriMatcher(UriMatcher.NO\_MATCH);  
![InBlock.gif][]        URI\_MATCHER.addURI("test", "item", ALL\_MESSAGES);  
![InBlock.gif][]        URI\_MATCHER.addURI("test", "item/\#", SPECIFIC\_MESSAGE);  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![InBlock.gif][]    // Here's the public URI used to query for RSS items.  
![InBlock.gif][]    public static final Uri CONTENT\_URI = Uri  
![InBlock.gif][]            .parse("content://test/item");  
![InBlock.gif][]  
![InBlock.gif][]    // Here are our column name constants, used to query for field values.  
![InBlock.gif][]    public static final String ID = "\_id";  
![InBlock.gif][]    public static final String NAME = "NAME";  
![InBlock.gif][]    public static final String VALUE = "VALUE";  
![InBlock.gif][]    public static final String DEFAULT\_SORT\_ORDER = ID \+ " DESC";  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    private static class DatabaseHelper extends AbstractDatabaseHelper ![dot.gif][]\{  
![InBlock.gif][]  
![InBlock.gif][]        @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        protected String\[\] createDBTables() ![dot.gif][]\{  
![InBlock.gif][]            // TODO Auto-generated method stub  
![InBlock.gif][]            String sql = "CREATE TABLE " \+ DATABASE\_TABLE\_NAME \+ "(" \+ ID  
![InBlock.gif][]                    \+ " INTEGER PRIMARY KEY AUTOINCREMENT, " \+ NAME \+ " TEXT,"  
![InBlock.gif][]                    \+ VALUE \+ " TEXT);";  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            return new String\[\] ![dot.gif][]\{ sql \};  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        protected String\[\] dropDBTables() ![dot.gif][]\{  
![InBlock.gif][]            // TODO Auto-generated method stub  
![InBlock.gif][]            return null;  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        protected String getDatabaseName() ![dot.gif][]\{  
![InBlock.gif][]            // TODO Auto-generated method stub  
![InBlock.gif][]            return DATABASE\_NAME;  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        protected int getDatabaseVersion() ![dot.gif][]\{  
![InBlock.gif][]            // TODO Auto-generated method stub  
![InBlock.gif][]            return DB\_VERSION;  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        protected String getTag() ![dot.gif][]\{  
![InBlock.gif][]            // TODO Auto-generated method stub  
![InBlock.gif][]            return TestContentProvider.class.getSimpleName();  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\* \*//\*\*  
![InBlock.gif][]     \*   
![ExpandedSubBlockEnd.gif][]     \*/  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    public TestContentProvider() ![dot.gif][]\{  
![InBlock.gif][]        // TODO Auto-generated constructor stub  
![InBlock.gif][]          
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#delete(android.net.Uri,  
![InBlock.gif][]     \* java.lang.String, java.lang.String\[\])  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    public int delete(Uri uri, String selection, String\[\] selectionArgs) ![dot.gif][]\{  
![InBlock.gif][]        // NOTE Argument checking code omitted. Check your parameters!  
![InBlock.gif][]        int rowCount = mDb.delete(DATABASE\_TABLE\_NAME, selection, selectionArgs);  
![InBlock.gif][]  
![InBlock.gif][]        // Notify any listeners and return the deleted row count.  
![InBlock.gif][]        getContext().getContentResolver().notifyChange(uri, null);  
![InBlock.gif][]        return rowCount;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#getType(android.net.Uri)  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    public String getType(Uri uri) ![dot.gif][]\{  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        switch (URI\_MATCHER.match(uri)) ![dot.gif][]\{  
![InBlock.gif][]        case ALL\_MESSAGES:  
![InBlock.gif][]            return "vnd.android.cursor.dir/rssitem"; // List of items.  
![InBlock.gif][]        case SPECIFIC\_MESSAGE:  
![InBlock.gif][]            return "vnd.android.cursor.item/rssitem"; // Specific item.  
![InBlock.gif][]        default:  
![InBlock.gif][]            return null;  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#insert(android.net.Uri,  
![InBlock.gif][]     \* android.content.ContentValues)  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    public Uri insert(Uri uri, ContentValues values) ![dot.gif][]\{  
![InBlock.gif][]        // NOTE Argument checking code omitted. Check your parameters! Check that  
![InBlock.gif][]        // your row addition request succeeded!  
![InBlock.gif][]  
![InBlock.gif][]       long rowId = \-1;  
![InBlock.gif][]       rowId = mDb.insert(DATABASE\_TABLE\_NAME, NAME, values);  
![InBlock.gif][]       Uri newUri = Uri.withAppendedPath(CONTENT\_URI, ""\+rowId);  
![InBlock.gif][]       Log.i("TestContentProvider", "saved a record " \+ rowId \+ " " \+ newUri);  
![InBlock.gif][]       // Notify any listeners and return the URI of the new row.  
![InBlock.gif][]       getContext().getContentResolver().notifyChange(CONTENT\_URI, null);  
![InBlock.gif][]       return newUri;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#onCreate()  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    @Override  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    public boolean onCreate() ![dot.gif][]\{  
![InBlock.gif][]        // TODO Auto-generated method stub  
![InBlock.gif][]        try  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            mDbHelper = new DatabaseHelper();  
![InBlock.gif][]            mDbHelper.open(getContext());  
![InBlock.gif][]            mDb = mDbHelper.getMDb();  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        \}catch(Exception e)![dot.gif][]\{  
![InBlock.gif][]            e.printStackTrace();  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        return true;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#query(android.net.Uri,  
![InBlock.gif][]     \* java.lang.String\[\], java.lang.String, java.lang.String\[\],  
![InBlock.gif][]     \* java.lang.String)  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    public Cursor query(Uri uri, String\[\] projection, String selection,  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            String\[\] selectionArgs, String sortOrder) ![dot.gif][]\{  
![InBlock.gif][]        // We won't bother checking the validity of params here, but you should!  
![InBlock.gif][]  
![InBlock.gif][]        // SQLiteQueryBuilder is the helper class that creates the  
![InBlock.gif][]        // proper SQL syntax for us.  
![InBlock.gif][]        SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();  
![InBlock.gif][]  
![InBlock.gif][]        // Set the table we're querying.  
![InBlock.gif][]        qBuilder.setTables(DATABASE\_TABLE\_NAME);  
![InBlock.gif][]  
![InBlock.gif][]        // If the query ends in a specific record number, we're  
![InBlock.gif][]        // being asked for a specific record, so set the  
![InBlock.gif][]        // WHERE clause in our query.  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        if((URI\_MATCHER.match(uri)) == SPECIFIC\_MESSAGE)![dot.gif][]\{  
![InBlock.gif][]            qBuilder.appendWhere("\_id=" \+ uri.getLastPathSegment());  
![InBlock.gif][]            Log.i("TestContentProvider", "\_id=" \+  uri.getLastPathSegment());  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]  
![InBlock.gif][]        // Make the query.  
![InBlock.gif][]        Cursor c = qBuilder.query(mDb,  
![InBlock.gif][]                projection,  
![InBlock.gif][]                selection,  
![InBlock.gif][]                selectionArgs,  
![InBlock.gif][]                null,  
![InBlock.gif][]                null,  
![InBlock.gif][]                sortOrder);  
![InBlock.gif][]        Log.i("TestContentProvider", "get records");  
![InBlock.gif][]        c.setNotificationUri(getContext().getContentResolver(), uri);  
![InBlock.gif][]        return c;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    /\*\*//\*  
![InBlock.gif][]     \* (non-Javadoc)  
![InBlock.gif][]     \*   
![InBlock.gif][]     \* @see android.content.ContentProvider\#update(android.net.Uri,  
![InBlock.gif][]     \* android.content.ContentValues, java.lang.String, java.lang.String\[\])  
![ExpandedSubBlockEnd.gif][]     \*/  
![InBlock.gif][]    @Override  
![InBlock.gif][]    public int update(Uri uri, ContentValues values, String selection,  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            String\[\] selectionArgs) ![dot.gif][]\{  
![InBlock.gif][]        // NOTE Argument checking code omitted. Check your parameters!  
![InBlock.gif][]        int updateCount = mDb.update(DATABASE\_TABLE\_NAME, values, selection, selectionArgs);  
![InBlock.gif][]  
![InBlock.gif][]        // Notify any listeners and return the updated row count.  
![InBlock.gif][]        getContext().getContentResolver().notifyChange(uri, null);  
![InBlock.gif][]        return updateCount;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]  
![ExpandedBlockEnd.gif][]\}   
![None.gif][]

配置文件如下：

![None.gif][]          < provider  android:name ="TestContentProvider"   
![None.gif][]            android:authorities ="test" >   
![None.gif][]         </ provider >

在客户端中可以使用如下方法进行调用：

![None.gif][]                 ContentValues values  =   new  ContentValues();  
![None.gif][]                values.put(TestContentProvider.NAME,  " testname1 " );  
![None.gif][]                values.put(TestContentProvider.VALUE,  " testvalu1e " );  
![None.gif][]                Uri newAddUri  =  TestActivity. this .getContentResolver().insert(TestContentProvider.CONTENT\_URI, values);  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]                Cursor c  =  TestActivity. this .managedQuery(newAddUri,  new  String\[\] ![dot.gif][] \{TestContentProvider.NAME\} ,  null ,  null ,  null );  
![None.gif][]                Log.i( " TestActivity " ,  ""   \+  c.getCount());  
![None.gif][]                 if (c.moveToNext())  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]                 ![dot.gif][] \{  
![InBlock.gif][]                    Log.i("TestActivity", c.getString(0));  
![ExpandedBlockEnd.gif][]                \}

上面的代码是先进行插入，然后进行查询并打印。就是如此简单，所有的应用如果需要都可以对外方便的提供数据接口，同时其他应用也可以很方便的进行调用。

[ExpandedBlockStart.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ExpandedBlockStart.gif
[ContractedBlock.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ContractedBlock.gif
[InBlock.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/InBlock.gif
[ExpandedBlockEnd.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ExpandedBlockEnd.gif
[None.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/None.gif
[dot.gif]: /images/20220708/07c6206b470d4e5f9d48f59d0209ef8b.png
[ExpandedSubBlockStart.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ExpandedSubBlockStart.gif
[ContractedSubBlock.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ContractedSubBlock.gif
[ExpandedSubBlockEnd.gif]: http://writeblog.csdn.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif