While implementing a complex UI layout in Android, it is very useful to get a good picture of the bounds (the border) of different components within the UI. For instance, if a relative layout’s position is modified programmatically, getting the bounds of the relative layout is useful. This helps in figuring out if a layout’s final position in the screen is in harmony with the expected position of the layout in the UI design. This also gives a good visual indicator of the distance between components when (say) RelativeLayout.below is specified.
In order to do this, turn on developer mode in Android. Then select Settings -> Developer Options -> Show layout bounds. This will draw blue rectangles on every UI component for all applications.