What is setContentView(R.layout.main)?

Solution 1:

In Android the visual design is stored in XML files and each Activity is associated to a design.

setContentView(R.layout.main)

R means Resource

layout means design

main is the xml you have created under res->layout->main.xml

Whenever you want to change the current look of an Activity or when you move from one Activity to another, the new Activity must have a design to show. We call setContentView in onCreate with the desired design as argument.

Solution 2:

As per the documentation :

Set the activity content from a layout resource. The resource will be inflated, adding all top-level views to the activity.

Your Launcher activity in the manifest first gets called and it set the layout view as specified in respective java files setContentView(R.layout.main);. Now this activity uses setContentView(R.layout.main) to set xml layout to that activity which will actually render as the UI of your activity.

Solution 3:

Why setContentView() in Android Had Been So Popular Till Now?

setContentView(int layoutid) - method of activity class. It shows layout on screen.

R.layout.main - is an integer number implemented in nested layout class of R.java class file.

At the run time device will pick up their layout based on the id given in setcontentview() method.

Solution 4:

Set the activity content from a layout resource. The resource will be inflated, adding all top-level views to the activity.

• Activity is basically a empty window
• SetContentView is used to fill the window with the UI provided from layout file incase of setContentView(R.layout.somae_file).
• Here layoutfile is inflated to view and added to the Activity context(Window).