RemoteViews原理分析及应用

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1、RemoteViews原理分析及应用RemoteViews基本概念RemoteViews乍一看名字似乎也是一种View，实则不然，它并不是View。来看RemoteViews的定义及官方说明：/***Aclassthatdescribesaviewhierarchythatcanbedisplayedin*anotherprocess.Thehierarchyisinflatedfromalayoutresource*file,andthisclassprovidessomebasicoperationsformodifying*thecontentoftheinflatedhiera

2、rchy.*/publicclassRemoteViewsimplementsParcelable,Filter{……}我们可以得到以下几点结论：RemoteViews只是一个实现了Parcelable和Filter接口的类，而并非继承自View。RemoteViews用来描述可运行在其他进程中的视图结构，但RemoteViews本身不是视图，只是一个描述类。RemoteViews描述的远程视图需要通过layout资源文件定义。RemoteViews类提供了一系列修改远程视图的方法。现在我们对RemoteViews应该有了一个大概的认识，它可以跨进程来显示和更新视图。RemoteVie

3、ws主要有两个应用场景：自定义通知栏桌面小部件本文最后会给出RemoteViews的应用实例，接下来我们先分析RemoteViews的实现原理。RemoteViews原理分析构造函数RemoteViews提供了多个构造函数，如：publicRemoteViews(StringpackageName,intlayoutId){}publicRemoteViews(StringpackageName,intuserId,intlayoutId){}publicRemoteViews(RemoteViewslandscape,RemoteViewsportrait){}publicRemot

4、eViews(Parcelparcel){}以一个最常用的构造方法为例：/***CreateanewRemoteViewsobjectthatwilldisplaytheviewscontained*inthespecifiedlayoutfile.**@parampackageNameNameofthepackagethatcontainsthelayoutresource*@paramlayoutIdTheidofthelayoutresource*/publicRemoteViews(StringpackageName,intlayoutId){this(getApplicati

5、onInfo(packageName,UserHandle.myUserId()),layoutId);}由注释可知，第一个参数为包名，第二个参数为布局资源文件的ID，接下来会调用：/***CreateanewRemoteViewsobjectthatwilldisplaytheviewscontained*inthespecifiedlayoutfile.**@paramapplicationTheapplicationwhosecontentisshownbytheviews.*@paramlayoutIdTheidofthelayoutresource.**@hide*/prot

6、ectedRemoteViews(ApplicationInfoapplication,intlayoutId){mApplication=application;mLayoutId=layoutId;mBitmapCache=newBitmapCache();//setupthememoryusagestatisticsmMemoryUsageCounter=newMemoryUsageCounter();recalculateMemoryUsage();}同样也很简单，第一个参数为远程视图展示内容所属的Application信息，第二个参数为布局文件ID。该构造方法主要是初始化mA

7、pplication与mLayoutId，其他代码为图片缓存及内存计算的一些逻辑。核心属性字段RemoteView有如下几个比较重要的属性字段：/***Applicationthathoststheremoteviews.**@hide*/privateApplicationInfomApplication;/***TheresourceIDofthelayoutfile.(Addedtotheparcel)*/privatefinalintm