Introduction

On Android, retrieving a view's dimensions is mainly about timing. A View does not have meaningful width and height values until the layout pass has measured and positioned it, so the correct answer is usually not just “call getWidth(),” but “call it after layout has happened.”

Why getWidth() Can Return Zero

If you query a view too early, such as inside onCreate, the view may not have been measured yet:

val width = myView.width
val height = myView.height

Those values can be zero even though the layout XML clearly defines a size. The problem is lifecycle timing, not the XML.

Use post for a Simple After-Layout Callback

A common approach is:

1myView.post {
2    val width = myView.width
3    val height = myView.height
4    println("$width x $height")
5}

post schedules the block to run after the view has been added to the message queue, which is often late enough for layout values to exist.

Use a Layout Listener for More Control

If you need an explicit signal when layout finishes, use ViewTreeObserver:

1myView.viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
2    override fun onGlobalLayout() {
3        myView.viewTreeObserver.removeOnGlobalLayoutListener(this)
4        val width = myView.width
5        val height = myView.height
6        println("$width x $height")
7    }
8})

This is useful when you need to react exactly once after measurement.

Know the Difference Between Measured and Actual Size

Android also exposes measured dimensions:

• 'measuredWidth'
• 'measuredHeight'

These represent the result of measurement, while width and height represent the actual laid-out size. In many cases they match, but conceptually they are different steps in the layout pipeline.

Prefer the Right Hook for the Job

A practical rule is:

• use post for simple one-time access
• use a layout listener when you need explicit lifecycle control
• read width and height only after layout

That is usually enough for view sizing tasks such as animation setup, custom drawing, or responsive layout adjustments.

onLayoutChangeListener Is Another Option

If you need to react whenever a view changes size, not just once, attach an OnLayoutChangeListener. That is different from a one-time post callback and is useful for views whose dimensions change after rotation or dynamic content updates.

Window Size and View Size Are Different

Do not confuse the dimensions of a specific view with the size of the device window or screen. A view may occupy only part of the available space, so read the actual view values rather than assuming they match the display.

Common Pitfalls

• Reading view dimensions inside onCreate before layout has happened.
• Confusing measuredWidth with the final laid-out width.
• Adding a global layout listener and forgetting to remove it.
• Assuming XML size values mean runtime dimensions are immediately available.
• Debugging the layout file when the real problem is lifecycle timing.

Measurement Bugs Usually Come from Asking Too Early

When view dimensions look wrong, the first suspicion should be lifecycle timing rather than XML attributes. Most “zero width” problems are really “not measured yet” problems.

Different Hooks Solve Different Layout Questions

Use a one-time callback when you only need the size once, and use a listener when the size may change repeatedly. Choosing the right hook keeps the UI code simpler.

Summary

• Android view dimensions are only reliable after measurement and layout.
• 'width and height can be zero if queried too early.'
• 'post is the simplest way to read dimensions after layout.'
• 'ViewTreeObserver gives more explicit control when needed.'
• Distinguish measured size from final laid-out size when debugging.