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android – "Avoid passing null as the view root" warning when inflating view for use by AlertDialog

Posted by: admin March 11, 2020 Leave a comment

Questions:

I get the lint warning, Avoid passing null as the view root when inflating views with null as parent, like:

LayoutInflater.from(context).inflate(R.layout.dialog_edit, null);

However, the view is to be used as the content of an AlertDialog, using setView on AlertDialog.Builder, so I don’t know what should be passed as the parent.

What do you think the parent should be in this case?

How to&Answers:

Use this code to inflate the dialog view without a warning:

View.inflate(context, R.layout.dialog_edit, null);

Answer:

The short story is that when you are inflating a view for a dialog, parent should be null, since it is not known at View inflation time. In this case, you have three basic solutions to avoid the warning:

  1. Suppress the warning using an @Suppress
  2. Inflate the View using View’s inflate method. This is just a wrapper around a LayoutInflater, and mostly just obfuscates the problem.
  3. Inflate the View using LayoutInflater’s full method: inflate(int resource, ViewGroup root, boolean attachToRoot). Set attachToRoot to false.This tells the inflater that the parent is not available. In older versions of Android Lint, this removed the warning. This is no longer the case in post 1.0 versions of Android Studio.

Check out http://www.doubleencore.com/2013/05/layout-inflation-as-intended/ for a great discussion of this issue, specifically the “Every Rule Has an Exception” section at the end.

Answer:

Casting null as ViewGroup resolved the warning:

View dialogView = li.inflate(R.layout.input_layout,(ViewGroup)null);

where li is the LayoutInflater's object.

Answer:

You should use AlertDialog.Builder.setView(your_layout_id), so you don’t need to inflate it.

Use AlertDialog.findViewById(your_view_id) after creating the dialog.

Use (AlertDialog) dialogInterface to get the dialog inside the OnClickListener and then dialog.findViewById(your_view_id).

Answer:

You don’t need to specify a parent for a dialog.

Suppress this using @SuppressLint("InflateParams") at the top of the override.

Answer:

When you really don’t have any parent (for example creating view for AlertDialog), you have no other choice than passing null. So do this to avoid warning:

final ViewGroup nullParent = null;
convertView = infalInflater.inflate(R.layout.list_item, nullParent);

Answer:

  1. The AlertDialog is as far as I know the only case were you can safely use null instead of a parent view. In this case you can suppress the warning by using:

    @SuppressLint(“InflateParams”)

  2. In general you should never use SupressLint or one of the workarounds mentioned in the other answers to get rid of the warning. The parent view is necessary to evaluate the Layout Params which are declared in the root element of the View being inflated. That means if you use null instead of the parent view, all Layout Params in the root element will be ignored and replaced by default Layout Params. Most of the time it will be fine, but in some cases it will result in a really hard-to-find bug.

Answer:

From the documentation of View.inflate(), it says

Inflate a view from an XML resource. This convenience method wraps the
LayoutInflater class, which provides a full range of options for view inflation.

  @param context The Context object for your activity or application.
  @param resource The resource ID to inflate
  @param root A view group that will be the parent.  Used to properly inflate the  layout_* parameters.

Answer:

Instead of doing

view = inflater.inflate(R.layout.list_item, null);

do

view = inflater.inflate(R.layout.list_item, parent, false);

It will inflate it with the given parent, but won’t attach it to the parent.

Many thanks to Coeffect (link to his post)