FrameLayout to RelativeLayout ClassCastException even if there is no FrameLayout used

Question

In my application, I have a layout which has a RelativeLayout to which I want to set margins at runtime programmatically. But when I do that, it gives me

Answer 1

Try setting FrameLayout.LayoutParams instead if RelativeLayout.LayoutParams. When you set the layout params at runtime, you have to set the ones from it's parent.

So, it'll be:

FrameLayout.LayoutParams _rootLayoutParams = new FrameLayout.LayoutParams(_rootLayout.getWidth(), _rootLayout.getHeight());
_rootLayoutParams.setMargins(300, 0, 300, 0);
_rootLayout.setLayoutParams(_rootLayoutParams);

Answer 2

I suggest that the parent of the @id/rl_root must be FrameLayout which is not showing in this xml. LayoutParam's type should be the same with its parent not itself.

Answer 3

I've had this error once before and it was because I tried to cast the parameters instead of creating a new instance. I hope this helps.

Right here :

RelativeLayout.LayoutParams _rootLayoutParams = new RelativeLayout.LayoutParams(_rootLayout.getWidth(), _rootLayout.getHeight());

Should be:

RelativeLayout.LayoutParams _rootLayoutParams = new RelativeLayout.LayoutParams(_rootLayout.getLayoutParams());

Now that you have all the layout parameters from the parent (root) layout, you can use them to set the parameters for your child view that you are inflating.

// Example usage:   
// viewGroup is the parent in this case whose parameters we want as a reference point.
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(viewGroup.getLayoutParams());

// Now we can add a rule stating that we want to center our new view both horizontally and vertically in the parent (viewGroup) view.
params.addRule(RelativeLayout.CENTER_IN_PARENT);

// Add more rules here if you would like
params.addRule(newRule2);

// After all of your new parameters are laid out, assign them to the view you want them applied to  
newView.setLayoutParams(params);

// Add the view to your hierarchy and enjoy
viewGroup.addView(newView);