CODEWITHSUNDEEP
javaandroidandroid-layoutandroid-view
Mr.
Mr.

Reputation: 10102

Android - findViewById() and dynamically setting ID's

I have a poll of ID's (ids.xml), and I assign id's for views I create dynamically. Now my question is pretty simple - assume I create a new view and assign it an id with setId() in conjuction with R.id.uniqueId. Later on, can I access the view with findViewById(R.id.uniqueId)?

If so, what could be the reason it returns null?

Here is a toy example: UPDATED

LinearLayout l = new LinearLayout(this);
l.setId(R.id.mId);
setContentView(l); //i see on screen the views added to 'l'
l = (LinearLayout) findViewById(R.id.mId); //it returns null :(

How come it does not register\map the assgined ID to the view it was assigned?

Upvotes: 0

Views: 2350

Answers (3)

Ratnakar
Ratnakar

Reputation: 163

encountered this many times, try cleaning your project by making a clean, Also check findViewById() returns null for custom component in layout XML, not for other components

Upvotes: 1

Bill
Bill

Reputation: 413

From what you have given us it appears that the view is never added to the Activity's view. This is necessary as findViewById uses the activity's view as a parent to find a child view with that Id.

If you are creating the view you can always create it as a member variable and refer to it that way if you are going to be adding it to a view at a later time. Please note that the view must be added after the id has been set.

Upvotes: 0

Jon O
Jon O

Reputation: 6591

Does your desired view have a parent view that you could use to call parent.findViewById on? That may help narrow your problem down.

One thing I noticed that's missing from your brief example: you need to make sure you're adding the new LinearLayout to the view hierarchy before you will be able to find it with findViewById:

findViewById(R.id.parent).addView(l)

You can also use the hierarchy viewer to take a look and see if everything's being set up properly.

Upvotes: 2

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