Question

For example,we have pixels. However, pixels are not constant. I would imagine that high resolution android screens will have more pixels.

Then we have density, which doesn’t seem to help a lot. It’s not as precise as pixels and still not constant. A high resolution will have high numbers of “densities”

Do we have something like 10% of screen size. Is it common among programmers to do so?

Answer 1

Never (or almost never) work with absolute pixels.

If you want to work with percentages of a screen’s layout then use layout_weight.

The following condensed XML layout file shows a vertical LinearLayout with two TextView widgets each within their own LinearLayouts. The inner LinearLayouts have their height set to 0dp but the ‘sum’ of the ‘weights’ (0.9 + 0.1) equals 1 therefore the first inner LinearLayout gets automatically expanded to 90% of the height of the screen whilst the second gets 10%.

The numbers you use don’t matter…they could be 9 & 1 or 90 & 10 or 900 & 100…it comes down to the total sum and what each represents as a percentage. The layout inflation process will do the rest without you needing to know about absolute pixels.

<LinearLayout
    android:orientation="vertical"
    ... >
    <LinearLayout
        ...
        android:layout_height="0dp"
        android:layout_weight="0.9" >
        <Textview
            ... >
    </LinearLayout>
    <LinearLayout
        ...
        android:layout_height="0dp"
        android:layout_weight="0.1" >
        <Textview
            ... >
    </LinearLayout>
</LinearLayout>