Android: Recyclerview In A Scrollview

I'm trying to have a RecyclerView inside a ScrollView. My problem is that when i scroll the RecyclerView this is not 'smooth': as soon as you release your finger the scrolling stop

Solution 1:

This problem has wrecked my night. :)

Observations

When RecyclerView is on the first screen (visible without scrolling), preceding views impact its height. When RecyclerView is initially fully invisible (requires scrolling the whole screen down), its height is correct.

Reason

When LinearLayout inside ScrollView measures its children, it passes how many pixels left as a MeasureSpec with mode UNSPECIFIED. RecyclerView passes this spec to LayoutManager, and it obeys passed height, if it is not null, even it is UNSPECIFIED.

Solution

Extend RecyclerView and override RecyclerView#onMeasure and, when height measure spec is UNSPECIFIED, just pass zero to super.onMeasure.

Java:

@OverrideprotectedvoidonMeasure(int widthSpec, int heightSpec) {
    super.onMeasure(
        widthSpec,
        MeasureSpec.getMode(heightSpec) == MeasureSpec.UNSPECIFIED ? 0 : heightSpec
    )
}

Kotlin:

overridefunonMeasure(widthSpec: Int, heightSpec: Int) {
    super.onMeasure(
        widthSpec,
        if (MeasureSpec.getMode(heightSpec) == MeasureSpec.UNSPECIFIED) 0else heightSpec
    )
}