Dynamically inflates UI in Android App_dynamic inflate android-优快云博客

本文探讨了在Android应用中动态加载UI布局的方法，并尝试通过从服务器下载XML布局文件实现UI的动态膨胀。然而，由于Android系统为了提高性能对XML布局文件进行了预处理，直接使用XmlPullParser的方式无法实现预期的效果。

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Dynamically inflates UI in Android App

There is a fascinating idea that inflates UI according to an android layout xml downloaded from server. According to the Android API, it looks quite feasible.

One of LayoutInflate.inflate method overloads accept Layout Xml as XmlPullParser.

And XmlPullParser can wrap around an input stream, so as consequence, following code seems to be working:

Inflate view on the fly

      
      
       public 
       class DynamicView extends FrameLayout {
      
      
          
       public 
       DynamicView(Context context, InputStream layoutData) 
       throws XmlPullParserException {
      
              
       super(context);
      
      
      
               createView(context, layoutData);
      
      
           }
      
      
          
       private 
       void 
       createView(Context context, InputStream layoutData) 
       throws XmlPullParserException {
      
      
               LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
      
      
      
               XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
      
      
               factory.setNamespaceAware(
       true);
      
      
               XmlPullParser parser = factory.newPullParser();
      
      
      
               parser.setInput(layoutData, 
       "UTF-8");
      
      
      
               inflater.inflate(parser, 
       this, 
       true);
      
      
           }
      
      
       }

The code looks great, compiling looks fine, but when the code excuted, an exception is thrown by the inflater.

According to the LayoutInflater document, this approach won’t work(at least for now, it won’t).

For performance reasons, view inflation relies heavily on pre-processing of XML files that is done at build time. Therefore, it is not currently possible to use LayoutInflater with an XmlPullParser over a plain XML file at runtime.
LayoutInflater Document developer.android.com

Actually, Android compiler compiles the layout xml files into binary xml block, which has convert attributes into some special format. And in Android SDK, the LayoutInflater uses XmlResourceParser instead of plain XmlPullParser, which is created byXmlBlock.

XmlBlock is an internal class used in Resources to cache the binary xml document.

And there is no way to create XmlResourceParser or other classes to inject custom behavior into this process. Personally assume that it is pretty much related to the Android Resource and Theming mechanism, there are quite a number cross references between resources. To make it works in a efficient way, Android Runtime did a lot work, such as cache and pre-processing. To override this behavior require quite a number of work and need to aware of potential performance issue. Since the inflating could happen quite often during navigation.

As a not that fansy alternative, UI based on HTML hosted in WebView could be considered.

转自：http://timnew.me/blog/2013/12/13/dynamically-inflates-ui-in-android-app/