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....

Answer 1

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).

Answer 2

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:

<LinearLayout      android:layout_width="match_parent"     android:layout_height="match_parent">     <view         class="com.company.MyCustomView"         android:layout_width="match_parent"         android:layout_height="match_parent" /> </LinearLayout>