What is setContentView(R.layout.main)?

Question

I understand that it has to do with the App layout, but when do I have to use it? I tried to look for a link that explained this method, but I couldn't find it. Thank you in advance!

Here is a nice visual explanation of [Android setContentView](https://androidride.com/what-setcontentview-android-studio/) — Athira Reddy, Jun 04 '19 at 03:49

score 65 · Answer 1 · edited Feb 10 '20 at 13:32

65

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.

edited Feb 10 '20 at 13:32

vwvw

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answered Jul 11 '14 at 20:56

Zare Ahmer

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What does it do? How do we use it? Why are we forced to use it? – Niklas Rosencrantz Nov 21 '17 at 06:24
what if you do not call setContentView at all? – George Shalvashvili Dec 30 '21 at 14:11
When building an Android app with C code (i.e. NDK), is there a C-language equivalent of `setContentView` and `R.layout.main`? – mercury0114 Sep 25 '22 at 22:15

CodeWarrior · Answer 2 · 2014-07-11T21:12:58.277

13

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.

edited Jul 11 '14 at 21:12

answered Jul 11 '14 at 20:52

CodeWarrior

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This documentation comes from the version of `setContentView()` which takes a `View` parameter. – Code-Apprentice Jul 11 '14 at 21:05
@Code-Apprentice Thanks for correcting. Working for 16 hrs now need some sleep :) – CodeWarrior Jul 11 '14 at 21:16

Thomas Daniel · Answer 3 · 2019-06-06T23:47:21.150

10

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.

edited Jun 06 '19 at 23:47

answered May 22 '18 at 06:37

Thomas Daniel

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score 3 · Answer 4 · edited Apr 09 '18 at 09:16

3

You can set content view (or design) of an activity. For example you can do it like this too :

public void onCreate(Bundle savedinstanceState) {
    super.onCreate(savedinstanceState);

    Button testButon = new Button(this);

    setContentView(testButon);   
}

Also watch this tutorial too.

edited Apr 09 '18 at 09:16

ColdFire

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answered Jul 11 '14 at 21:07

Lazy

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score 3 · Answer 5 · answered Jul 20 '17 at 19:32

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).

What is setContentView(R.layout.main)?

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