Expansion after init does not work

[esnaultdev]

Hello, thank you for the library.

I stumbled on a bug while using the expansion panel in a recycler view. I need to handle the expansion manually, so I'm using collapse(boolean animated) and expand(boolean animated) to update the expansion layout accordingly.

It works fine, except when initializing the layout state to expanded. The layout is not expanded by default (in the XML) but set to expanded (expand(false)) by the adapter when the activity starts.

I think the cause is:

• expand(false) is called by the adapter. expanded is set to true, but we don't have a height yet
• the ViewTreeObserver for preDraw is called
• the preDraw callback tries to update the height of the layout since it's expanded https://github.com/florent37/ExpansionPanel/blob/ffd431de78a51c594d1d78f4c46697708105a878/expansionpanel/src/main/java/com/github/florent37/expansionpanel/ExpansionLayout.java#L133-L136
• expand(false) is called but returns early since expanded is true https://github.com/florent37/ExpansionPanel/blob/ffd431de78a51c594d1d78f4c46697708105a878/expansionpanel/src/main/java/com/github/florent37/expansionpanel/ExpansionLayout.java#L207-L210
• and so, setHeight is never called with the expanded height

If that's the case, I think updating the preDraw callback to

//now we have a size
if (expanded) {
    setHeight(getChildAt(0).getHeight());
}

might be the fix. I can do a PR for this if you want.

The same problem seem to be present in the horizontal version, though I haven't tested it.

[patelapps]

@AoDevBlue You can use separate thread to handle such case. It may help

[pomacanthus]

+1 on this issue Thanks for the lib and thanks @esnaultdev for the fix idea, it should be PR'd :)

In the meanwhile I made myself a workaround with a subclass of expansion layout

class ExpansionLayout2(context: Context, attrs: AttributeSet?) : ExpansionLayout(context, attrs) {

    override fun expand(animated: Boolean) {

        if (isExpanded() && isEnabled()) {
            val height = getChildAt(0).getHeight();
            // setHeight(height)
            // setHeight is private, so let's copy its contents instead of calling it :
            val layoutParams = layoutParams
            if (layoutParams != null) {
                layoutParams.height = height
                setLayoutParams(layoutParams)
            }
        }
        else
            expand(animated, true)
    }
}

and for sure replacing in the layout file

            <com.github.florent37.expansionpanel.ExpansionLayout
                android:id="@+id/myExpansionLayoutId2"
                android:layout_height="wrap_content"
                android:layout_width="match_parent">

                <!-- CONTENT -->
             
            </com.github.florent37.expansionpanel.ExpansionLayout>

with

            <mypackage.path.ExpansionLayout2
                android:id="@+id/myExpansionLayoutId2"
                android:layout_height="wrap_content"
                android:layout_width="match_parent">

                <!-- CONTENT -->
             
            </mypackage.path.ExpansionLayout2>