How to size an Android view based on its parent s dimensions

Question

How can I size a view based on the size of its parent layout  For example I have a RelativeLayout that fills the full screen  and I want a child view  say an ImageView  to take up the whole height  and 1 2 the width   I ve tried overriding all on onMeasure  onLayout  onSizeChanged  etc and I couldn t get it to work

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I ve been struggling this question for a long time  I want to change my DrawerLayout s drawer width  which is the second child of its parent  Recently I figured it out  but doesn t know if there s a better idea   override fun onLayout changed  Boolean  l  Int  t  Int  r  Int  b  Int        super onLayout changed  l  t  r  b       getChildAt 1  layoutParams as LayoutParams  width   measuredWidth 2

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I ve found that it s best not to mess around with setting the measured dimensions yourself  There s actually a bit of negotiation that goes on between the parent and child views and you don t want to re-write all that code   What you can do  though  is modify the measureSpecs  then call super with them  Your view will never know that it s getting a modified message from its parent and will take care of everything for you    Override protected void onMeasure int widthMeasureSpec  int heightMeasureSpec        int parentHeight   MeasureSpec getSize heightMeasureSpec       int myWidth    int   parentHeight   0 5       super onMeasure MeasureSpec makeMeasureSpec myWidth  MeasureSpec EXACTLY   heightMeasureSpec

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When you define a layout and view on XML  you can specify the layout width and height of a view to either be wrap content  or fill parent   Taking up half of the area is a bit harder  but if you had something you wanted on the other half you could do something like the following        lt LinearLayout android layout width  fill parent                  android layout height  fill parent  gt           lt ImageView android layout height  fill parent                   android layout width  0dp                   android layout weight  1   gt           lt ImageView android layout height  fill parent                   android layout width  0dp                   android layout weight  1   gt      lt  LinearLayout gt    Giving two things the same weight means that they will stretch to take up the same proportion of the screen   For more info on layouts  see the dev docs

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You can now use PercentRelativeLayout  Boom  Problem solved

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I don t know if anyone is still reading this thread or not  but Jeff s solution will only get you halfway there  kinda literally   What his onMeasure will do is display half the image in half the parent  The problem is that calling super onMeasure prior to the setMeasuredDimension will measure all the children in the view based on the original size  then just cut the view in half when the setMeasuredDimension resizes it   Instead  you need to call setMeasuredDimension  as required for an onMeasure override  and provide a new LayoutParams for your view  then call super onMeasure  Remember  your LayoutParams are derived from your view s parent type  not your view s type    Override  protected void onMeasure int widthMeasureSpec  int heightMeasureSpec      int parentWidth   MeasureSpec getSize widthMeasureSpec      int parentHeight   MeasureSpec getSize heightMeasureSpec      this setMeasuredDimension parentWidth 2  parentHeight      this setLayoutParams new  ParentLayoutType  LayoutParams parentWidth 2 parentHeight       super onMeasure widthMeasureSpec  heightMeasureSpec       I believe the only time you ll have problems with the parent LayoutParams is if the parent is an AbsoluteLayout  which is deprecated but still sometimes useful

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It s something like this    lt RelativeLayout xmlns android  http   schemas android com apk res android      xmlns tools  http   schemas android com tools      android layout width  match parent      android layout height  match parent      tools context  com company myapp ActivityOrFragment      android id    id activity or fragment  gt    lt LinearLayout     android layout width  match parent      android layout height  wrap content      android id    id linearLayoutFirst      android weightSum  100  gt     lt  -- Overall weights sum of children elements -- gt        lt Spinner         android layout width  0dp     lt  -- It s 0dp because is determined by android layout weight -- gt          android layout weight  50          android layout height  wrap content          android id    id spinner    gt    lt  LinearLayout gt     lt LinearLayout     android layout height  wrap content      android layout width  match parent      android layout below    id linearLayoutFirst      android layout alignParentLeft  true      android layout alignParentStart  true      android id    id linearLayoutSecond  gt        lt EditText         android layout height  wrap content          android layout width  0dp          android layout weight  75          android inputType  numberDecimal          android id    id input    gt        lt TextView         android layout height  wrap content          android layout width  0dp          android layout weight  25          android id    id result   gt    lt  LinearLayout gt   lt  RelativeLayout gt

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If the other side is empty  I guess the simplest way would be to add an empty view  e g  a linear layout  then set both views  widths to fill parent and both their weights to 1   This works in a LinearLayout

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I believe that Mayras XML-approach can come in neat  However it is possible to make it more accurate  with one view only by setting the weightSum  I would not call this a hack anymore but in my opinion the most straightforward approach    lt LinearLayout android layout width  fill parent                android layout height  fill parent                android weightSum  1  gt       lt ImageView android layout height  fill parent                 android layout width  0dp                 android layout weight  0 5   gt   lt  LinearLayout gt    Like this you can use any weight  0 6 for instance  and centering  is the weight I like to use for buttons

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Roman  if you want to do your layout in Java code  ViewGroup descendant   it is possible  The trick is that you have to implement both onMeasure and onLayout methods   The onMeasure gets called first and you need to  measure  the subview  effectively sizing it to the desired value  there  You need to size it again in the onLayout call  If you fail to do this sequence or fail to call setMeasuredDimension   at the end of your onMeasure code  you won t get results  Why is this designed in such complicated and fragile way is beyond me

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You could solve this by creating a custom View and override the onMeasure   method  If you always use  fill parent  for the layout width in your xml then the widthMeasureSpec parameter that is passed into the onMeasusre   method should contain the width of the parent   public class MyCustomView extends TextView        public MyCustomView Context context  AttributeSet attrs            super context  attrs               Override     protected void onMeasure int widthMeasureSpec  int heightMeasureSpec            super onMeasure widthMeasureSpec  heightMeasureSpec            int parentWidth   MeasureSpec getSize widthMeasureSpec           int parentHeight   MeasureSpec getSize heightMeasureSpec           this setMeasuredDimension parentWidth   2  parentHeight                Your XML would look something like this    lt LinearLayout      android layout width  match parent      android layout height  match parent  gt       lt view         class  com company MyCustomView          android layout width  match parent          android layout height  match parent    gt   lt  LinearLayout gt

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Try this  int parentWidth     parentViewType childView getParent    getWidth    int parentHeight     parentViewType childView getParent    getHeight      then you can use LinearLayout LayoutParams for setting the chileView s parameters  LinearLayout LayoutParams params   new LinearLayout LayoutParams childWidth childLength   childView setLayoutParams params

[android] How to size an Android view based on its parent's dimensions

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