content provider write

发布时间：2020-12-17 01:26:05 所属栏目：安全来源：网络整理

导读：reference: http://jlins.javaeye.com/blog/561434 ?如果需要创建你自己的cotent?provider,也就是定制自己特有的，你需要做的其实很简单，那就是从抽象类ContentProvider派生出你自己的类，并且实现里面所有的抽象方法，包括：?? ? query(Uri,?String[],?Str

reference: http://jlins.javaeye.com/blog/561434

?如果需要创建你自己的cotent?provider,也就是定制自己特有的，你需要做的其实很简单，那就是从抽象类ContentProvider派生出你自己的类，并且实现里面所有的抽象方法，包括：??

query(Uri,?String[],?String,?String)?which?returns?data?to?the?caller??

insert(Uri,?ContentValues)?which?inserts?new?data?into?the?content?provider??

update(Uri,?ContentValues,?String[])?which?updates?existing?data?in?the?content?provider??

delete(Uri,?String[])?which?deletes?data?from?the?content?provider??

getType(Uri)?which?returns?the?MIME?type?of?data?in?the?content?provider??

在你的content?provider里面，你有随意选择存储媒介的权利，你可以用传统文件，xml，甚至是一些特定的web?service,?当然你也可以选择用的最为广泛的SQLite??

在你自己的类中，你需要定义一个public?static?final?Uri?命名为CONTENT_URI。??

public?class?BooksProvider?extends?ContentProvider??

{??
???public?static?final?String?PROVIDER_NAME?=??
??????"MyContentProvider";????
??
???public?static?final?Uri?CONTENT_URI?=??
??????Uri.parse("content://"+?PROVIDER_NAME?+?"/books");????
??
???public?static?final?String?_ID?=?"_id";??
???public?static?final?String?TITLE?=?"title";??
???public?static?final?String?ISBN?=?"isbn";??
???private?static?final?int?BOOKS?=?1;??
???private?static?final?int?BOOK_ID?=?2;???????
???private?static?final?UriMatcher?uriMatcher;??
??
???static{??
??????uriMatcher?=?new?UriMatcher(UriMatcher.NO_MATCH);??
??????uriMatcher.addURI(PROVIDER_NAME,?"books",?BOOKS);??
??????uriMatcher.addURI(PROVIDER_NAME,?"books/#",?BOOK_ID);??
???}??

//---for?database?use---??
???private?SQLiteDatabase?booksDB;??
???private?static?final?String?DATABASE_NAME?=?"Books";??
???private?static?final?String?DATABASE_TABLE?=?"titles";??
???private?static?final?int?DATABASE_VERSION?=?1;??
???private?static?final?String?DATABASE_CREATE?=??
?????????"create?table?"?+?DATABASE_TABLE?+??
?????????"?(_id?integer?primary?key?autoincrement,?"??
?????????+?"title?text?not?null,?isbn?text?not?null);";????
??
???@Override??
???public?boolean?onCreate()?{??
??????Context?context?=?getContext();??
??????DatabaseHelper?dbHelper?=?new?DatabaseHelper(context);??
??????booksDB?=?dbHelper.getWritableDatabase();??
??????return?(booksDB?==?null)??false:true;??
???}??

?private?static?class?DatabaseHelper?extends?SQLiteOpenHelper??
???{??
??????DatabaseHelper(Context?context)?{??
?????????super(context,?DATABASE_NAME,?null,?DATABASE_VERSION);??
??????}??
??
???
??????@Override??
??????public?void?onCreate(SQLiteDatabase?db)??
??????{??
?????????db.execSQL(DATABASE_CREATE);??
??????}??
????
??????@Override??
??????public?void?onUpgrade(SQLiteDatabase?db,?int?oldVersion,??
??????int?newVersion)?{??
?????????Log.w("Content?provider?database",??
??????????????"Upgrading?database?from?version?"?+??
??????????????oldVersion?+?"?to?"?+?newVersion?+??
??????????????",?which?will?destroy?all?old?data");??
?????????db.execSQL("DROP?TABLE?IF?EXISTS?titles");??
?????????onCreate(db);??
??????}??
???}?

?@Override??
???public?String?getType(Uri?uri)?{??
??????switch?(uriMatcher.match(uri)){??
?????????//---get?all?books---??
?????????case?BOOKS:??
????????????return?"vnd.android.cursor.dir/vnd.learn2develop.books?";??
?????????//---get?a?particular?book---??
?????????case?BOOK_ID:??
????????????return?"vnd.android.cursor.item/vnd.learn2develop.books?";??
?????????default:??
????????????throw?new?IllegalArgumentException("Unsupported?URI:?"?+?uri);??
??????}??
???}??

??@Override??
???public?Cursor?query(Uri?uri,?String[]?projection,?String?selection,??
??????String[]?selectionArgs,?String?sortOrder)?{??????
??
??????SQLiteQueryBuilder?sqlBuilder?=?new?SQLiteQueryBuilder();??
??????sqlBuilder.setTables(DATABASE_TABLE);??????
??
??????if?(uriMatcher.match(uri)?==?BOOK_ID)??
?????????//---if?getting?a?particular?book---??
?????????sqlBuilder.appendWhere(??
????????????_ID?+?"?=?"?+?uri.getPathSegments().get(1));?????????
??
??????if?(sortOrder==null?||?sortOrder=="")??
?????????sortOrder?=?TITLE;??
??
?????????Cursor?c?=?sqlBuilder.query(??
?????????booksDB,??
?????????projection,??
?????????selection,??
?????????selectionArgs,??
?????????null,??
?????????null,??
?????????sortOrder);??
??
??????//---register?to?watch?a?content?URI?for?changes---??
??????c.setNotificationUri(getContext().getContentResolver(),?uri);??
??????return?c;??
???}??

@Override??
???public?Uri?insert(Uri?uri,?ContentValues?values)?{??
??????//---add?a?new?book---??
??????long?rowID?=?booksDB.insert(??
?????????DATABASE_TABLE,?"",?values);?????????????
??
??????//---if?added?successfully---??
??????if?(rowID>0)??
??????{??
?????????Uri?_uri?=?ContentUris.withAppendedId(CONTENT_URI,?rowID);??
?????????getContext().getContentResolver().notifyChange(_uri,null);???
?????????return?_uri;??
??????}??
??
??????throw?new?SQLException("Failed?to?insert?row?into?"?+?uri);??
???}??
????
???@Override??
???public?int?delete(Uri?arg0,?String?arg1,?String[]?arg2)?{??
??????//?arg0?=?uri???
??????//?arg1?=?selection??
??????//?arg2?=?selectionArgs??
??
??????int?count=0;??
??????switch?(uriMatcher.match(arg0)){??
?????????case?BOOKS:??
????????????count?=?booksDB.delete(??
???????????????DATABASE_TABLE,??
???????????????arg1,??
???????????????arg2);??
??
????????????break;??
??
?????????case?BOOK_ID:??
????????????String?id?=?arg0.getPathSegments().get(1);??
????????????count?=?booksDB.delete(??
???????????????DATABASE_TABLE,??
???????????????_ID?+?"?=?"?+?id?+??
???????????????(!TextUtils.isEmpty(arg1)???"?AND?("?+??
???????????????arg1?+?')'?:?""),??
???????????????arg2);??
????????????break;??
??
?????????default:?throw?new?IllegalArgumentException(??
????????????"Unknown?URI?"?+?arg0);???
??
??????}???
??
??????getContext().getContentResolver().notifyChange(arg0,?null);??
??
??????return

（编辑：李大同）

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