我的android 第26天 - Contant Provider

我的android 第26天 - Contant Provider

   介绍：Contant Provider 内容提供者，android四大组件之一，使用于多个应用同时使用同一份数据。它对不同的数据存储(file\sqlite\intent)进行了封装,提供了统一的数据访问方式.android系统内部很多内容都以内容提供者的形式共享输出，比如联系人信息、短信等

 案例：采用Contant Provider 共享SQLite person表的数据，

  实现增删改查等操作

一、Contant Provider机制

二、采用内容提供者共享数据实现过程

1、继承ContantProvider，重写以下方法

•boolean onCreate()：创建ContantProvider时调用

•Uriinsert(Uri uri, ContentValues values)

插入操作

•int delete(Uri uri,String selection, String[] selectionArgs)：删除操作

• intupdate(Uri uri, ContentValues values, String selection, String[]selectionArgs)：更新操作

• Cursor query(Uri uri,String[] projection, String selection, String[] selectionArgs, String sortOrder)：查询操作

•StringgetType(Uri uri)：返回数据的MINE-TYPE

•

2、内容提供者为android四大组件之一，需要在AndroidManifest.xml中注册

 

public class PersonProvider extends ContentProvider {static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);private static final int MULTI = 1;private static final int SINGLE = 2;static {// content://cn.itcast.sqlite.providers.personprovider/personmatcher.addURI("cn.itcast.sqlite.providers.personprovider", "person", MULTI);//  content://cn.itcast.sqlite.providers.personprovider/person/4matcher.addURI("cn.itcast.sqlite.providers.personprovider", "person/#", SINGLE);}DBHelper helper;/** * 初始化ContentProvider的时候调用 */public boolean onCreate() {helper = new DBHelper(getContext());return false;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {SQLiteDatabase db = helper.getReadableDatabase();switch (matcher.match(uri)) {case MULTI: //访问多条数据 content://cn.itcast.sqlite.providers.personprovider/personreturn db.query(PersonMgr.TABLE, projection, selection, selectionArgs, null, null, sortOrder);case SINGLE: // 访问单条数据 content://cn.itcast.sqlite.providers.personprovider/person/4// 解析Uri尾部的idlong id = ContentUris.parseId(uri);String where = PersonMgr.ID + " = " + id;if (selection!=null && !"".equals(selection.trim())) {where += " and " + selection;}return db.query(PersonMgr.TABLE, projection, where, selectionArgs, null, null, sortOrder);case UriMatcher.NO_MATCH: // uri不合法throw new IllegalArgumentException("uri不合法");}return null;}/** * 返回数据的MINE-TYPE ： image/jpeg  plain/text image/png */public String getType(Uri uri) {switch (matcher.match(uri)) {case MULTI: //多条数据 content://cn.itcast.sqlite.providers.personprovider/personreturn "vnd.android.cursor.dir/person";case SINGLE: // 单条数据 content://cn.itcast.sqlite.providers.personprovider/person/4return "vnd.android.cursor.item/person";case UriMatcher.NO_MATCH: // uri不合法throw new IllegalArgumentException("uri不合法");}return null;}@Overridepublic Uri insert(Uri uri, ContentValues values) {// content://cn.itcast.sqlite.providers.personprovider/personSQLiteDatabase db = helper.getWritableDatabase();switch (matcher.match(uri)) {case MULTI: // content://cn.itcast.sqlite.providers.personprovider/personlong id = db.insert(PersonMgr.TABLE, null, values); db.close();// 发出数据改变的通知getContext().getContentResolver().notifyChange(uri, null);return ContentUris.withAppendedId(uri, id);default: // uri不合法throw new IllegalArgumentException("uri不合法");}}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {SQLiteDatabase db = helper.getReadableDatabase();int result = 0;switch (matcher.match(uri)) {case MULTI: //多条数据 content://cn.itcast.sqlite.providers.personprovider/personresult =  db.delete(PersonMgr.TABLE, selection, selectionArgs);break;case SINGLE: // 单条数据 content://cn.itcast.sqlite.providers.personprovider/person/4String where = PersonMgr.ID + "=" + ContentUris.parseId(uri);if (selection != null && !"".equals(selection.trim())) {where += " and " + selection;}result =  db.delete(PersonMgr.TABLE, where, selectionArgs);break;case UriMatcher.NO_MATCH: // uri不合法throw new IllegalArgumentException("uri不合法");}db.close();return result;}public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {SQLiteDatabase db = helper.getReadableDatabase();int result = 0;switch (matcher.match(uri)) {case MULTI: //多条数据 content://cn.itcast.sqlite.providers.personprovider/personresult =  db.update(PersonMgr.TABLE, values, selection, selectionArgs);break;case SINGLE: // 单条数据 content://cn.itcast.sqlite.providers.personprovider/person/4String where = PersonMgr.ID + "=" + ContentUris.parseId(uri);if (selection != null && !"".equals(selection.trim())) {where += " and " + selection;}result =  db.update(PersonMgr.TABLE, values, where, selectionArgs);break;case UriMatcher.NO_MATCH: // uri不合法throw new IllegalArgumentException("uri不合法");}db.close();return result;}}

三、关注点

 . 理解AndroidContantProvider机制

 . Uri格式

 

 . 运用UriMatcher匹配Uri

 

 .运用ContentUris为Uri添加或截取尾部的ID数据

   ContentUris.withAppendedId(uri, 10)：给Uri尾部添加10（id）

       ContentUris.parseId(uri);//获取尾部的id

   . 如何监听ContentProvider数据的改变

   .getType：返回所访问数据的minetype（image/jpeg plain/text 

      image/png）

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