What is Dalvik Virtual Machine

Dalvik is the process virtual machine DVM(Dalvik Virtual Machine) in Google Android operating system executes applications written for Android.

Its programs are commonly written in java compile to byte code for Java virtual machine. Dalvik bycode stored in .dex(Dalvik Executable) and .odex(Optimized Dalvik Executable) files.

Layout.xml File

The Android SDK includes a number of layout classes. Use the UI for your views, Fragments and Activities.

The following list includes commonly used layout classes available in the Android SDK.

  • Frame Layout
  • Linear Layout
  • relative Layout
  • Grid Layout


This simplest of the Layout Managers, the Frame Layout pins each child view with its frame. Adding multiple children stack each new child on top of the one before, with each new View potentially obscuring the previous ones. The default position top-left corner, use gravity attributes.

Linear Layout

A Linear Layout aligns each child View in either a vertical or a horizontal line. The Linear Layout supports a weight attribute for each child View that can control the relative size of each child View within the available space.

Relative Layout

One of the most flexible of the native layouts, the Relative Layout lets you define the positions of each child View relative to others and to the screen boundaries.


Introduction in Android 4.0(API level 14), the Grid Layout users a rectangular grid of infinity thin to layout Views in a series of rows and columns.

The Grid Layout is particularly useful for constructing layout that require alignment in two directions.