Nested weights are bad for performance in my XML code [duplicate]

Question

This question already has answers here:

Why are nested weights bad for performance? Alternatives? (6 answers)

Closed 4 years ago.

I want to display an organized grid. So I use LinearLayout and Layout Weight option, every thing works perfectly, but I don't understand how to avoid this warning in the Button A and the Button C:

Nested weights are bad for performance

And this is my XML code :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >

        <!-- First row. -->

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:weightSum="2" >

            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_weight="1"
                android:text="A" />

            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_marginTop="10dp"
                android:layout_weight="1"
                android:text="B" />
        </LinearLayout>

        <!-- Second row. -->

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:weightSum="2" >

            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_marginTop="10dp"
                android:layout_weight="1"
                android:text="C" />

            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_marginTop="10dp"
                android:layout_weight="1"
                android:text="D" />
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

How can I avoid this error please ?

Answer 1

You can only ignore this warning if you want to keep this layout.

Add to the root of your layout: xmlns:tools="http://schemas.android.com/tools". Then in your buttons add tools:ignore="NestedWeights".

This can be also done in eclipse by putting the cursor on the yellow line and pressing ctrl + 1. You can choose ignore.

---

If you want to improve performance, you can use a TableLayout

<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/tableLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
    <TableRow
        android:id="@+id/tableRow1"
        android:layout_weight="1"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:padding="5dip" >

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="A" />

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_marginTop="10dp"
            android:layout_weight="1"
            android:text="B" />
    </TableRow>
    <TableRow
        android:id="@+id/tableRow2"
        android:layout_weight="1"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:padding="5dip" >
            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_marginTop="10dp"
                android:layout_weight="1"
                android:text="C" />

            <Button
                android:layout_width="0dip"
                android:layout_height="fill_parent"
                android:layout_marginTop="10dp"
                android:layout_weight="1"
                android:text="D" />
    </TableRow>
</TableLayout>

Answer 2

This occurs because you could have performance impact while rendering the component, to be accomodate Layout to fix in parent a letter Button to fix accordingly Buttons to space of LinearLayout,just remove layout_weightof the LinearLayout

Answer 3

One way to avoid this warning is to flatten your layout by replacing the outer LinearLayout with a RelativeLayout.

The other thing that pops out to me is that the first child LinearLayout is completely unnecessary. It has only one child (another LinearLayout), so it isn't really doing anything.

With a RelativeLayout, you can simplify this layout to:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/row1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:weightSum="2" >

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="A" />

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_marginTop="10dp"
            android:layout_weight="1"
            android:text="B" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/row2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_below="@+id/row1"
        android:weightSum="2" >

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_marginTop="10dp"
            android:layout_weight="1"
            android:text="C" />

        <Button
            android:layout_width="0dip"
            android:layout_height="fill_parent"
            android:layout_marginTop="10dp"
            android:layout_weight="1"
            android:text="D" />
    </LinearLayout>

</RelativeLayout>