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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!

user3814312
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    Here is a nice visual explanation of [Android setContentView](https://androidride.com/what-setcontentview-android-studio/) – Athira Reddy Jun 04 '19 at 03:49

6 Answers6

62

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.

vwvw
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Zare Ahmer
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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.

CodeWarrior
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9

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.

Thomas Daniel
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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.

ColdFire
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Lazy
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3

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).
Babavali Sheik
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0

in order to explain the method setContentView(:int) which takes a layout file as a parameter.

so let's imagine i want to create a view and add to it a button :

enter image description here

so in android , the setContentView will only takes an xml file (layout) and inflate it to an empty activity.

at the end to add my customized view which contains a button to the empty activity i will only use the same method setContentView(v).

Anouar Bakouch
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