How to avoid nested weights?

Question

I have a xml layout to enter a pincode:

<?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:background="#FF000000"
    android:orientation="vertical"
    android:weightSum="1" >

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_margin="5dp"
    android:layout_weight="0.2"
    android:background="@android:drawable/edit_text"
    android:gravity="center_vertical"
    android:orientation="horizontal" >

    <EditText
        android:id="@+id/pinDisplay"
        android:layout_width="0dip"
        android:layout_height="fill_parent"
        android:layout_weight="0.85"
        android:background="@null" />

    <ImageButton
        android:id="@+id/backspace"
        style="@android:style/Widget.Button"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_gravity="center_vertical"
        android:layout_margin="3dp"
        android:layout_weight="0.15"
        android:gravity="center"
        android:src="@android:drawable/ic_input_delete" />
</LinearLayout>

<!-- Keypad section -->

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_weight="0.8"
    android:baselineAligned="false"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="4dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/one"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="1"
            android:textAppearance="@android:attr/text" />

        <Button
            android:id="@+id/two"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="2" />

        <Button
            android:id="@+id/three"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="3" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0sp"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="4dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/four"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="4" />

        <Button
            android:id="@+id/five"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="5" />

        <Button
            android:id="@+id/six"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="6" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0sp"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="4dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/seven"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="7" />

        <Button
            android:id="@+id/eight"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="8" />

        <Button
            android:id="@+id/nine"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="9" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0sp"
        android:layout_marginBottom="10dip"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="4dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/ok"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:enabled="false"
            android:text="OK"
            android:textColor="#B8B8B8" />

        <Button
            android:id="@+id/zero"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="0" />

        <Button
            android:id="@+id/clear"
            android:layout_width="0sp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="Clear" />
    </LinearLayout>
  </LinearLayout>
</LinearLayout>

The layout is fine, but I get a lot of Lint warnings about nested weights.

Nested weights are bad for performance

I don't really notice the layout loading slow or anything. What can I do to avoid nested weights? Or should I just leave it like it is?

Answer 1

In general, you should try to use a RelativeLayout instead of nesting many LinearLayouts.

From documentation:

Note: Although you can nest one or more layouts within another layout to acheive your UI design, you should strive to keep your layout hierarchy as shallow as possible. Your layout draws faster if it has fewer nested layouts (a wide view hierarchy is better than a deep view hierarchy).

But when you need weights, like now, a RelativeLayout wouldn't help you much; instead, I suggest using a TableLayout for your keypad, to reduce the number of nested layouts.

Answer 2

You could use RelativeLayout to avoid the nested weights.

Nested weights are bad for performance because the number of measurements increase exponentially with each one nested.