Question

why should i put android:layout_width="0px" when i use android:layout_weight property? For example following is my main.xml file , and in that i used android:layout_width="wrap_content", and everything works fine, so why android:layout_width="0px" should be used when i am using the layout_weight property?

<?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="horizontal">
<EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/editText" android:hint="enter your name"
        android:layout_weight="3"/>
<Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send"
        android:id="@+id/button"
        android:layout_weight="0"/>
</LinearLayout>

and this is how my layout looks:

Answer 1

You certainly don’t have to. Additionally weight=0 doesn’t make much sense. The weight parameter controls what part of the remaining space in the layout the widget occupies. So setting width=0 effectively tells it to take up only the remaining space. If you set width=30, it will occupy 30 px|dp + all the remaining space. Setting 0 as the width makes it easier to get a predictable result on different screen sizes.

A common pattern is to have two widgets with width=0 and equal weight to make them equally sized inside the parent container, where you don’t care about the actual size (width or height).