Question: I notice that there is a tag `<view>`(not `<View>`) which can be used in Android layout xml. When I add such a tag in a layout xml, the app can be successfully compiled but crashes when running. So what is this `<view>` used for?

Answer: 
`view` is an alternative way for specifying a view to inflate. You need to combine it with `class` attribute to specify the class name.

This is "useful" if your view class is an inner class and you cannot use something with a `$` in the tag name in XML. (Having inner classes as `View`s you inflate is not a very good idea though.)

For example:

```
<view class="your.app.full.package.Something$InnerClass" ... />

```

Reference: <http://androidxref.com/5.0.0_r2/xref/frameworks/base/core/java/android/view/LayoutInflater.java#696>
View is widget of android that is use to add any kind of view.Like in problems when we use scrollView in a activity and at bottom of activity there is buttons ,That time we add view to looks better.We can set any kind of color to View .
for exp 

 This will make a View of 20dp height.