注册ContentProvider:
<provider android:name=".provider.UserProvider" android:authorities="com.rw.contentprovider.provider.UserProvider" android:exported="true" ></provider>其中authorities是URI中的域名部分，可以随便取，但必须在整个系统中唯一
name和ACtivity一样，告诉虚拟机与之绑定的class
exported指定ContentProvider是否允许被其他应用调用
继承ContentProvider的以下5个方法：
可以根据自己的业务需求，实现相应的方法
以下是自己写的demo，有之前写的DBOpenHelper类的支持
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { SQLiteDatabase dataBase= this.userDatabase.getReadableDatabase(); switch (USERMATCHER.match(uri)) { case USER: long rawId= ContentUris.parseId(uri); String where="uid="+rawId; if(selection!=null){ where+=" and "+selection; } return dataBase.query("users", projection, where, selectionArgs, null, null,sortOrder); case USERS: return dataBase.query("users", projection, selection, selectionArgs, null,null, sortOrder); default: throw new IllegalArgumentException("this unknown Uri:"+uri.toString()); } }
public String getType(Uri uri) { switch (USERMATCHER.match(uri)) { case USER: return "vnd.android.cursor.dir/user"; case USERS: return "vnd.android.cursor.item/user"; default: throw new IllegalArgumentException("this is unknown Uri:"+uri.toString()); } }
public Uri insert(Uri uri, ContentValues values) { SQLiteDatabase dataBase= this.userDatabase.getWritableDatabase(); switch (USERMATCHER.match(uri)) { case USER: throw new IllegalArgumentException("this Uri can not insert a record to Content!"); case USERS: long rawId=dataBase.insert("users", null, values); return ContentUris.withAppendedId(uri, rawId); default: throw new IllegalArgumentException("this unknown Uri:"+uri.toString()); } }
public int delete(Uri uri, String selection, String[] selectionArgs) { SQLiteDatabase dataBase= this.userDatabase.getWritableDatabase(); switch (USERMATCHER.match(uri)) { case USER: long rawId= ContentUris.parseId(uri); String where="uid="+rawId; if(selection!=null){ where+=" and "+selection; } return dataBase.delete("users", where, selectionArgs); case USERS: return dataBase.delete("users", selection, selectionArgs); default: throw new IllegalArgumentException("this unknown Uri:"+uri.toString()); } }
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { SQLiteDatabase dataBase=userDatabase.getWritableDatabase(); switch (USERMATCHER.match(uri)) { case USER: long rawId= ContentUris.parseId(uri); String where="uid="+rawId; if(selection!=null){ where+=" and "+selection; } return dataBase.update("users", values, where, selectionArgs); case USERS: if(selection!=null){ return dataBase.update("users", values, selection, selectionArgs); }else{ throw new IllegalArgumentException("this Uri con not update record from dataBase"); } default: throw new IllegalArgumentException("this Uri is unknown:"+uri.toString()); } }
在使用者使用ContentResolver对数据进行CURD操作时,分别调用了与之对应的的方法，其实其底层也是根据URI获取到了这个ContentProvider,进而将参数传递给ContentProvider中与之对应的方法。以下是其中一类的Code
public final int update(Uri uri, ContentValues values, String where, String[] selectionArgs) { //在这里根据传入的Uri，获取到一个ContentProvider IContentProvider provider = acquireProvider(uri); if (provider == null) { throw new IllegalArgumentException("Unknown URI " + uri); } try { long startTime = SystemClock.uptimeMillis(); //在这里真正执行ContentProvider的update方法 int rowsUpdated = provider.update(mPackageName, uri, values, where, selectionArgs); long durationMillis = SystemClock.uptimeMillis() - startTime; maybeLogUpdateToEventLog(durationMillis, uri, "update", where); return rowsUpdated; } catch (RemoteException e) { // Arbitrary and not worth documenting, as Activity // Manager will kill this process shortly anyway. return -1; } finally { releaseProvider(provider); } }