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ContentProvider主要用于在不同應(yīng)用程序之間實(shí)現(xiàn)數(shù)據(jù)共享功能。允許一個(gè)程序訪問(wèn)另一個(gè)程序，并保證被訪數(shù)據(jù)的安全性。

Android系統(tǒng)自帶的電話簿、短信、媒體庫(kù)等提供了類似的接口。還可以通過(guò)新建一個(gè)類繼承ContentProvider自定義自己的內(nèi)容提供器。

Google Doc對(duì)ContentProvider的部分描述：

內(nèi)容提供者繼承自ContentProvider基類，為其他應(yīng)用程序取用和存儲(chǔ)管理數(shù)據(jù)實(shí)現(xiàn)了一套標(biāo)準(zhǔn)方案，但應(yīng)用程序并不直接調(diào)用這些方法，而是使用ContentResolver對(duì)象，調(diào)用它的方法作為代替。

example

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package?sunny.example.contactstest;import?java.util.ArrayList;import?android.support.v7.app.ActionBarActivity;import?android.database.Cursor;import?android.os.Bundle;import?android.provider.ContactsContract; import?android.widget.ArrayAdapter;import?android.widget.ListView;import?java.util.List;public?class?MainActivity?extends?ActionBarActivity?{ListView?contactsView;ArrayAdapter<String>?adapter;List<String>?contactsList?=?new?ArrayList<String>();@Overrideprotected?void?onCreate(Bundle?savedInstanceState)?{super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);contactsView?=?(ListView)findViewById(R.id.contacts_view);/*android.widget.ArrayAdapter.ArrayAdapter<String>(Context?context,?int?textViewResourceId,?List<String>?objects)*Parameters:context?The?current?context.textViewResourceId?The?resource?ID?for?a?layout?file?containing?a?TextView?to?use?when?instantiating?views.objects?The?objects?to?represent?in?the?ListView.*/adapter?=?new?ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,contactsList);//void?android.widget.ListView.setAdapter(ListAdapter?adapter)contactsView.setAdapter(adapter);readContacts();}private?void?readContacts(){/*android.database.CursorThis?interface?provides?random?read-write?accessto?the?result?set?returned?by?a?database?query. */Cursor?cursor?=?null;try{/**?ContentResolver?android.content.ContextWrapper.getContentResolver()*?Return?a?ContentResolver?instance?for?your?application's?package.?*//*要訪問(wèn)ContentProvider中共享的數(shù)據(jù)就要借助getContentResolver類，通過(guò)getContentResolver（）方法*?獲取該類的實(shí)例，利用其中提供的方法對(duì)數(shù)據(jù)進(jìn)行CRUD操作（Create/Retrieve/Delete）*/cursor?=?getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,?null,?null,?null,?null);while(cursor.moveToNext()){String?displayName?=?cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));String?number?=?cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));contactsList.add(displayName+"\n"+number);}????}catch(Exception?e){e.printStackTrace();}finally{if(cursor!=null){cursor.close();}}???}}

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創(chuàng)建自己的內(nèi)容提供器

//DatabaseProvider.java創(chuàng)建數(shù)據(jù)庫(kù) package?sunny.example.databasetest;import?android.content.ContentProvider;import?android.content.ContentValues;import?android.content.UriMatcher;import?android.database.Cursor;import?android.database.sqlite.SQLiteDatabase;import?android.net.Uri;public?class?DatabaseProvider?extends?ContentProvider{public?static?final?int?BOOK_DIR?=?0;public?static?final?int?BOOK_ITEM?=?1;public?static?final?int?CATEGORY_DIR?=?2;public?static?final?int?CATEGORY_ITEM?=?3;public?static?final?String?AUTHORITY?=?"sunny.example.databasetest.provider";private?MyDatabaseHelper?dbHelper;private?static?UriMatcher?uriMatcher;/*void?android.content.UriMatcher.addURI(String?authority,?String?path,?int?code) Add?a?URI?to?match,?and?the?code?to?return?when?this?URI?is?matched.?URI?nodes?may?be? exact?match?string,?the?token?"*"?that?matches?any?text,?or?the?token?"#"?that?matches? only?numbers. Parameters: authority?the?authority?to?match path?the?path?to?match.?*?may?be?used?as?a?wild?card?for?any?text,?and?#?may?be?used?as?a?wild?card?for?numbers. code?the?code?that?is?returned?when?a?URI?is?matched?against?the?given?components.?Must?be?positive.*/static{/*android.content.UriMatcher.UriMatcher(int?code)Creates?the?root?node?of?the?URI?tree.*/uriMatcher?=?new?UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(AUTHORITY,?"book",?BOOK_DIR);uriMatcher.addURI(AUTHORITY,?"book/#",?BOOK_ITEM);uriMatcher.addURI(AUTHORITY,?"category",?CATEGORY_DIR);uriMatcher.addURI(AUTHORITY,?"category/#",?CATEGORY_ITEM);}@Overridepublic?boolean?onCreate()?{//?TODO?Auto-generated?method?stubdbHelper?=?new?MyDatabaseHelper(getContext(),"BookStore.db",null,2);return?true;}@Overridepublic?Cursor?query(Uri?uri,?String[]?projection,?String?selection,String[]?selectionArgs,?String?sortOrder)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getReadableDatabase();Cursor?cursor?=?null;switch(uriMatcher.match(uri)){case?BOOK_DIR:cursor?=?db.query("book",projection,selection,selectionArgs,null,null,sortOrder);break;case?BOOK_ITEM:String?bookId?=?uri.getPathSegments().get(1);cursor?=?db.query("book",?projection,?"id?=??",?new?String[]{bookId},?null,null,?sortOrder);break;case?CATEGORY_DIR:cursor?=?db.query("category",?projection,?selection,?selectionArgs,null,?null,?sortOrder);break;case?CATEGORY_ITEM:String?categoryId?=?uri.getPathSegments().get(1);cursor?=?db.query("category",?projection,?"id?=??",new?String[]{categoryId},null,?null,?sortOrder);break;default:break;}return?null;}@Overridepublic?String?getType(Uri?uri)?{//?TODO?Auto-generated?method?stubswitch(uriMatcher.match(uri)){case?BOOK_DIR:return?"vnd.android.cursor.dir/vnd.com.example.app.provider.table1";case?BOOK_ITEM:return?"vnd.android.cursor.item/vnd.com.example.app.provider.table1";case?CATEGORY_DIR:return?"vnd.android.cursor.dir/vnd.com.example.app.provider.table2";case?CATEGORY_ITEM:return?"vnd.android.cursor.item/vnd.com.example.app.provider.table2";default:break;}return?null;}@Overridepublic?Uri?insert(Uri?uri,?ContentValues?values)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();Uri?uriReturn?=?null;switch(uriMatcher.match(uri)){case?BOOK_DIR:case?BOOK_ITEM:long?newBookId?=?db.insert("Book",?null,?values);uriReturn?=?uri.parse("content://"+AUTHORITY+"/book/"+newBookId);break;case?CATEGORY_DIR:case?CATEGORY_ITEM:long?newCategoryId?=?db.insert("Category",?null,?values);uriReturn?=?uri.parse("content://"+AUTHORITY+"/category"+newCategoryId);break;default:break;}return?uriReturn;}@Overridepublic?int?delete(Uri?uri,?String?selection,?String[]?selectionArgs)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();int?deleteRows?=?0;switch(uriMatcher.match(uri)){case?BOOK_DIR:deleteRows?=?db.delete("Book",?selection,?selectionArgs);break;case?BOOK_ITEM:String?bookId?=?uri.getPathSegments().get(1);deleteRows?=?db.delete("Book",??"id?=??",?new?String[]{bookId});break;case?CATEGORY_DIR:deleteRows?=?db.delete("Category",?selection,?selectionArgs);break;case?CATEGORY_ITEM:String?categoryId?=?uri.getPathSegments().get(1);deleteRows?=?db.delete("Category",?"id?=??",?new?String[]{categoryId});default:break;}return?deleteRows??;}@Overridepublic?int?update(Uri?uri,?ContentValues?values,?String?selection,String[]?selectionArgs)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();int?updateRows?=?0;switch(uriMatcher.match(uri)){case?BOOK_DIR:updateRows?=?db.update("Book",?values,?selection,?selectionArgs);break;case?BOOK_ITEM:String?bookId?=?uri.getPathSegments().get(1);updateRows?=?db.update("Book",?values,?"id?=??",?new?String[]{bookId});break;case?CATEGORY_DIR:updateRows?=?db.update("Category",?values,?selection,?selectionArgs);break;case?CATEGORY_ITEM:String?categoryId?=?uri.getPathSegments().get(1);updateRows?=?db.update("Category",?values,?"id?=??",?new?String[]{categoryId});default:break;}return?updateRows??;} } //MyDatabaseHelper.javapackage?sunny.example.databasetest;import?android.content.Context;import?android.database.sqlite.SQLiteDatabase;import?android.database.sqlite.SQLiteDatabase.CursorFactory;import?android.database.sqlite.SQLiteOpenHelper;import?android.widget.Toast;public?class?MyDatabaseHelper?extends?SQLiteOpenHelper{//將建表語(yǔ)句定義成一個(gè)字符常量public?static?final?String?CREATE_BOOK?=?"create?table?Book("+?"id?integer?primary?key?autoincrement,"+"author?text,"+"price?real,"+"pages?integer,"+"name?text)";public?static?final?String?CREATE_CATEGORY="create?table?Category("+"id?integer?primary?key?autoincrement,"+"category_name?text,"+"categpry_code?integer)";private?Context?mContext;public?MyDatabaseHelper(Context?context,?String?name,CursorFactory?factory,?int?version)?{//第二個(gè)參數(shù)：數(shù)據(jù)庫(kù)名。第三個(gè)參數(shù)：允許在查詢數(shù)據(jù)的時(shí)候返回一個(gè)自定義的Cursor.第四個(gè)參數(shù)：當(dāng)前數(shù)據(jù)庫(kù)版本號(hào)super(context,?name,?factory,?version);//?TODO?Auto-generated?constructor?stubmContext?=?context;}@Overridepublic?void?onCreate(SQLiteDatabase?db)?{//?TODO?Auto-generated?method?stubdb.execSQL(CREATE_BOOK);//執(zhí)行建表語(yǔ)句db.execSQL(CREATE_CATEGORY);Toast.makeText(mContext,?"Create?Succeeded",?Toast.LENGTH_SHORT).show();}@Overridepublic?void?onUpgrade(SQLiteDatabase?db,?int?oldVersion,?int?newVersion)?{//?TODO?Auto-generated?method?stubdb.execSQL("drop?table?if?exists?Book");db.execSQL("drop?table?if?exists?Category");onCreate(db);} } //MainActivity.javapackage?sunny.example.databasetest;import?android.support.v7.app.ActionBarActivity;import?android.content.ContentValues;import?android.database.Cursor;import?android.database.sqlite.SQLiteDatabase;import?android.os.Bundle;import?android.util.Log;import?android.view.Menu;import?android.view.MenuItem;import?android.view.View;import?android.view.View.OnClickListener;import?android.widget.Button;import?android.widget.TextView;public?class?MainActivity?extends?ActionBarActivity?{ //構(gòu)建MyDatabaseHelper對(duì)象private?MyDatabaseHelper?dbHelper;@Overrideprotected?void?onCreate(Bundle?savedInstanceState)?{super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);dbHelper?=?new?MyDatabaseHelper(this,"BookStore.db",null,2);//將數(shù)據(jù)庫(kù)名指定為BookStore.db，版本號(hào)指定為1dbHelper?=?new?MyDatabaseHelper(this,"BookStore.db",null,1);Button?createDatabase?=?(Button)findViewById(R.id.create_database);createDatabase.setOnClickListener(new?OnClickListener(){@Overridepublic?void?onClick(View?v)?{//?TODO?Auto-generated?method?stub//創(chuàng)建數(shù)據(jù)庫(kù)dbHelper.getWritableDatabase();}});Button?addData?=?(Button)findViewById(R.id.add_data);addData.setOnClickListener(new?OnClickListener(){@Overridepublic?void?onClick(View?v)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();ContentValues?values?=?new?ContentValues();values.put("name",?"A");values.put("author",?"Dan");values.put("pages",?12);values.put("price",0.7);db.insert("Book",null,values);}});Button?updateData?=?(Button)findViewById(R.id.update_data);updateData.setOnClickListener(new?OnClickListener(){@Overridepublic?void?onClick(View?v)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();ContentValues?values?=?new?ContentValues();values.put("price",?0.2);//將name等于A的price改成0.2db.update("Book",?values,?"name?=??",?new?String[]{"A"});}});Button?deleteData?=?(Button)findViewById(R.id.delete_data);deleteData.setOnClickListener(new?OnClickListener(){@Overridepublic?void?onClick(View?v)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();//刪去頁(yè)數(shù)超過(guò)500頁(yè)的書db.delete("Book",?"pages?>??",?new?String[]{"500"});}});Button?queryData?=?(Button)findViewById(R.id.query_data);queryData.setOnClickListener(new?OnClickListener(){@Overridepublic?void?onClick(View?v)?{//?TODO?Auto-generated?method?stubSQLiteDatabase?db?=?dbHelper.getWritableDatabase();Cursor?cursor?=?db.query("Book",?null,?null,?null,?null,?null,?null);/*Move?the?cursor?to?the?first?row.This?method?will?return?false?if?the?cursor?is?empty.Returns:whether?the?move?succeeded.*/if(cursor.moveToFirst()){do{String?name?=?cursor.getString(cursor.getColumnIndex("name"));String?author?=?cursor.getString(cursor.getColumnIndex("author"));int?pages?=?cursor.getInt(cursor.getColumnIndex("pages"));double?price?=?cursor.getDouble(cursor.getColumnIndex("price"));Log.d("MainActivity","book?name?is"?+?name);TextView?textView?=?(TextView)findViewById(R.id.textView);String?nameT?=?"book?name?is"?+?name;textView.setText(nameT);}while(cursor.moveToNext());}cursor.close();}});} } ?<providerandroid:name="sunny.example.databasetest.DatabaseProvider"android:authorities="sunny.example.databasetest.provider"android:exported="true"></provider>

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轉(zhuǎn)載于:https://my.oschina.net/doudoulee/blog/635024

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