內(nèi)容提供者 參考：
Android四大組件之內(nèi)容提供者--ContentProvider - java小兵 - CSDN博客
Android四大組件之內(nèi)容提供者--ContentProvider ?
B程序通過內(nèi)容提供者來訪問聯(lián)系人程序的數(shù)據(jù)。
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1，什么是ContentProvider ?
? ? ? ? ContentProvider將應(yīng)用中的數(shù)據(jù)對(duì)其它應(yīng)用進(jìn)行共享, 提供增刪改查的方法 ?
? ? ? ? ContentProvider統(tǒng)一了數(shù)據(jù)的訪問方式，不必針對(duì)不同數(shù)據(jù)類型采取不同的訪問策略 ?
? ? ? ? ContentProvider將數(shù)據(jù)封裝，只暴露出我們希望提供給其它程序的數(shù)據(jù) ?
? ? ? ? ContentProvider中可以注冊(cè)觀察者, 監(jiān)聽數(shù)據(jù)的變化 ??
2，怎么創(chuàng)建 ?
? ? ? ? 2.1定義類繼承ContentProvider, 實(shí)現(xiàn)抽象方法，抽象方法中對(duì)數(shù)據(jù)庫操作的增刪改查都有。 ?
? ? ? ? 2.2在清單文件中注冊(cè)：在清單文件的<application>節(jié)點(diǎn)下進(jìn)行配置<provider>標(biāo)簽，標(biāo)簽中需要指定name和authorities屬性 ?
? ? ? ? ? ? name：完整的類名。
? ? ? ? ? ? authorities：主機(jī)
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B程序需要通過com.baidu這個(gè)url來實(shí)現(xiàn)訪問修改讀取聯(lián)系人程序。
完整類名就是繼承ContentProvider類的那個(gè)類的完整類名。
這樣配置也是告訴計(jì)算機(jī)，我這個(gè)類是內(nèi)容提供者，后面要被別人訪問，并且可以通過com.baidu這個(gè)主機(jī)訪問我。
我們?cè)贐程序中通過內(nèi)容解析者和主機(jī)名訪問聯(lián)系人程序。
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3，在手機(jī)上注冊(cè) ContentResolver ContentResolver resolver = Context.getContentResolver(); 通過resolver.insert(), delete(), update(), query()方法訪問Uri關(guān)聯(lián)的ContentProvider
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5，Uri的處理 1，schema：表明要訪問ContentProvider。固定為："content://" 2，Authority(主機(jī)名或授權(quán))： 自定義 UriMatcher 和 ContentUris 1，UriMatcher類用于匹配Uri //如果match()方法匹配content://com.jxn.provider.personprovider/person路徑，返回匹配碼為1 //如果match()方法匹配content://com.jxn.provider.personprovider/person/230路徑，返回匹配碼為2
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6，監(jiān)聽內(nèi)容提供者數(shù)據(jù)變化?
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??????? 1，如果ContentProvider的訪問者需要知道ContentProvider中的數(shù)據(jù)發(fā)生了變化，可以在ContentProvider 發(fā)生數(shù)據(jù)變化時(shí)調(diào)用getContentResolver().notifyChange(uri, null)來通知注冊(cè)在此URI上的訪問者，例如：?
??????????? public class PersonContentProvider extends ContentProvider {?
??????????????? public Uri insert(Uri uri, ContentValues values) {?
??????????????????? db.insert("person", "personid", values);?
??????????????????? // 注：如果沒有調(diào)用notifyChange()方法，即使其它應(yīng)用注冊(cè)了ContentObserver，也不會(huì)知道ContentProvider中的數(shù)據(jù)的變化?
??????????????????? getContext().getContentResolver().notifyChange(uri, null);?
??????????????? }?
??????????? }?
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??????? 2，如果ContentProvider的訪問者需要得到數(shù)據(jù)變化通知，必須使用ContentObserver對(duì)數(shù)據(jù)(用uri描述)進(jìn)行監(jiān)聽，當(dāng)監(jiān)聽到數(shù)據(jù)變化通知時(shí)，系統(tǒng)就會(huì)調(diào)用ContentObserver的onChange()方法：?
??????????? getContentResolver().registerContentObserver(Uri.parse("content://com.jxn.providers.personprovider/person"),true, new PersonObserver(new Handler()));?
??????????? public class PersonObserver extends ContentObserver{?
??????????????? public PersonObserver(Handler handler) {?
??????????????????? super(handler);?
??????????????? }?
??????????????? public void onChange(boolean selfChange) {?
??????????????????? //此處可以進(jìn)行相應(yīng)的業(yè)務(wù)處理?
??????????????? }?
??????????? }??
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7，補(bǔ)充?
??????? getType()方法：主要用于匹配數(shù)據(jù)類型，返回當(dāng)前Uri所代表數(shù)據(jù)的MIME類型。?
??????????? 如果返回?cái)?shù)據(jù)是單條數(shù)據(jù)：vnd.android.cursor.item??
??????????? 如果返回?cái)?shù)據(jù)是多條數(shù)據(jù)：vnd.android.cursor.dir??
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案例：B應(yīng)用通過A應(yīng)用提供的ContentProvider訪問A應(yīng)用中的數(shù)據(jù)?? ?? ????//?提供ContentProvider的A應(yīng)用中定義的SQLiteProvider?? ????public?class?SQLiteProvider?extends?ContentProvider?{?? ?? ????????//?Uri匹配器,?用來匹配傳入的Uri?? ????????private?static?final?UriMatcher?matcher?=?new?UriMatcher(UriMatcher.NO_MATCH);?? ?????????? ????????private?static?final?int?PERSON?=?1;?? ?????????? ????????//?DBOpenHelper?extends?SQLiteOpenHelper?? ????????private?DBOpenHelper?helper;?? ?? ????????static?{?? ????????????//?設(shè)置一個(gè)Uri,?如果匹配到person,?返回1?? ????????????matcher.addURI("com.jxn.sqlite.provider",?"person",?PERSON);?? ????????}?? ?????????? ?? ????????//?其它應(yīng)用第一次訪問時(shí)(此時(shí)會(huì)創(chuàng)建ContentProvider)執(zhí)行?? ????????//?第一次啟動(dòng)時(shí)執(zhí)行,?然后會(huì)長(zhǎng)期駐留在后臺(tái),?除非被殺死,?否則不會(huì)再執(zhí)行?? ????????@Override?? ????????public?boolean?onCreate()?{?? ????????????helper?=?new?DBOpenHelper(getContext());?? ????????????return?true;?? ????????}?? ?? ????????//?外部應(yīng)用使用此方法查詢數(shù)據(jù)?? ????????@Override?? ????????public?Cursor?query(Uri?uri,?String[]?projection,?String?selection,?String[]?selectionArgs,?String?sortOrder)?{?? ????????????SQLiteDatabase?db?=?helper.getReadableDatabase();?? ?????????????? ????????????//?用匹配器匹配傳入的uri?? ????????????switch?(matcher.match(uri))?{?? ????????????????case?PERSON:?? ????????????????????return?db.query("person",?projection,?selection,?selectionArgs,?null,?null,?sortOrder);?????//?執(zhí)行查詢?? ????????????????default:?? ????????????????????throw?new?RuntimeException("Uri不能識(shí)別:?"?+?uri);?? ????????????}?? ????????}?? ?? ????????//?外部應(yīng)用使用此方法添加數(shù)據(jù)?? ????????@Override?? ????????public?Uri?insert(Uri?uri,?ContentValues?values)?{?? ????????????SQLiteDatabase?db?=?helper.getWritableDatabase();?? ????????????switch?(matcher.match(uri))?{?? ????????????????case?PERSON:?? ????????????????????long?id?=?db.insert("person",?"id",?values);????//?插入記錄,?得到id?? ????????????????????return?ContentUris.withAppendedId(uri,?id);?????//?把id跟在uri后面返回?? ????????????????default:?? ????????????????????throw?new?RuntimeException("Uri不能識(shí)別:?"?+?uri);?? ????????????}?? ????????}?? ?? ????????@Override?? ????????public?int?delete(Uri?uri,?String?selection,?String[]?selectionArgs)?{?? ????????????SQLiteDatabase?db?=?helper.getWritableDatabase();?? ????????????switch?(matcher.match(uri))?{?? ????????????????case?PERSON:?? ????????????????????return?db.delete("person",?selection,?selectionArgs);?? ????????????????default:?? ????????????????????throw?new?RuntimeException("Uri不能識(shí)別:?"?+?uri);?? ????????????}?? ????????}?? ?? ????????@Override?? ????????public?int?update(Uri?uri,?ContentValues?values,?String?selection,?String[]?selectionArgs)?{?? ????????????SQLiteDatabase?db?=?helper.getWritableDatabase();?? ????????????switch?(matcher.match(uri))?{?? ????????????????case?PERSON:?? ????????????????????return?db.update("person",?values,?selection,?selectionArgs);?? ????????????????default:?? ????????????????????throw?new?RuntimeException("Uri不能識(shí)別:?"?+?uri);?? ????????????}?? ????????}?? ?? ????????@Override?? ????????public?String?getType(Uri?uri)?{?? ????????????switch?(matcher.match(uri))?{?? ????????????????case?PERSON:?? ????????????????????return?"vnd.android.cursor.dir/person";?????//?mimetype?? ????????????????default:?? ????????????????????throw?new?RuntimeException("Uri不能識(shí)別:?"?+?uri);?? ????????????}?? ????????}?? ????}?? ?? ?? ????//?B應(yīng)用中要訪問A應(yīng)用的數(shù)據(jù)的測(cè)試類?? ????public?class?ProviderTest?extends?AndroidTestCase?{?? ?????????? ????????public?void?test()?{?? ?????????? ????????????//?獲取解析器對(duì)象?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ?????????????? ????????????//?訪問內(nèi)容提供者?? ????????????Uri?uri?=?Uri.parse("content://com.jxn.sqlite.provider");?? ????????????ContentValues?values?=?new?ContentValues();?? ?? ????????}?? ?????????? ????????public?void?testQuery()?{?? ?????????? ????????????//?獲取解析器對(duì)象?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ????????????Uri?uri?=?Uri.parse("content://com.jxn.sqlite.provider/person");?? ?????????????? ????????????//?訪問內(nèi)容提供者?? ????????????Cursor?c?=?resolver.query(uri,?new?String[]{?"id",?"name",?"balance"?},?"balance>?",?new?String[]{?"9000"?},?"balance?DESC");?? ????????????while?(c.moveToNext())?{?? ????????????????Person?p?=?new?Person(c.getInt(0),?c.getString(1),?c.getInt(2));?? ????????????????System.out.println(p);?? ????????????}?? ????????}?? ?????????? ????????public?void?testInsert()?{?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ????????????Uri?uri?=?Uri.parse("content://com.jxn.sqlite.provider/person");?? ?????????????? ????????????ContentValues?values?=?new?ContentValues();?? ????????????values.put("name",?"provider");?? ????????????values.put("balance",?12345);?? ?????????????? ????????????//?插入數(shù)據(jù),?并且得到這條數(shù)據(jù)的uri?? ????????????uri?=?resolver.insert(uri,?values);?? ?????????????? ????????????System.out.println(uri);?? ????????}?? ?????????? ????????public?void?testUpdate()?{?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ????????????Uri?uri?=?Uri.parse("content://com.jxn.sqlite.provider/person");?? ?????????????? ????????????ContentValues?values?=?new?ContentValues();?? ????????????values.put("name",?"update");?? ????????????values.put("balance",?54321);?? ????????????int?count?=?resolver.update(uri,?values,?null,?null);?? ????????????System.out.println(count);?? ????????}?? ?????????? ????????public?void?testDelete()?{?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ????????????Uri?uri?=?Uri.parse("content://com.jxn.sqlite.provider/person");?? ?????????????? ????????????int?count?=?resolver.delete(uri,?null,?null);?? ????????????System.out.println(count);?? ????????}?? ?????????? ????????public?void?testGetType()?{?? ????????????ContentResolver?resolver?=?getContext().getContentResolver();?? ????????????//?獲取uri的類型?? ????????????String?type?=?resolver.getType(Uri.parse("content://com.jxn.sqlite.provider/person"));?? ????????????System.out.println(type);?? ????????}?? ????} ? 轉(zhuǎn)載于:https://www.cnblogs.com/Renyi-Fan/p/7471659.html
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