Linear Layout and weight in Android_问答_开发者

I always read about this funny weight value in the Android documentations. Now I want to try it for the first time but it isn't working at all.

As I understand it from the documentations this layout:

  <LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="horizontal">

     <Button
        android:text="Register"
        android:id="@+id/register"
        android:layout_width="wrap_content"
        android:layout_he开发者_如何学Cight="wrap_content"
        android:padding="10dip"
        weight="1" />

     <Button
        android:text="Not this time"
        android:id="@+id/cancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="10dip"
        weight="1" />

  </LinearLayout>

should create two buttons that are horizontally aligned and share the space equally. The problem is the two buttons don't grow to fill the space.

I would like the buttons to grow and fill the whole line. If both buttons are set to match parent only the first button is shown and fills the whole line.

3 things to remember:

set the android:layout_width of the children to "0dp"
set the android:weightSum of the parent (edit: as Jason Moore noticed, this attribute is optional, because by default it is set to the children's layout_weight sum)
set the android:layout_weight of each child proportionally (e.g. weightSum="5", three children: layout_weight="1", layout_weight="3", layout_weight="1")

Example:

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:weightSum="5">

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="1" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="3"
        android:text="2" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="3" />

</LinearLayout>

And the result:

Linear Layout and weight in Android

You are not setting the layout_weight property. Your code reads weight="1" and it should read android:layout_weight="1".

It's android:layout_weight. Weight can only be used in LinearLayout. If the orientation of linearlayout is Vertical, then use android:layout_height="0dp" and if the orientation is horizontal, then use android:layout_width = "0dp". It'll work perfectly.

This image summarizes the Linear layout.

Linear Layout and weight in Android

You can follow this link for more information on the topic. Just Maths - Views, View Groups and Layouts

Video Tutorial For Linear Layout : Width, Height & Weights

Android Linear Layout Tutorial

Try setting the layout_width of both buttons to "0dip" and the weight of both buttons to 0.5

LinearLayout supports assigning a weight to individual children. This attribute assigns an "importance" value to a view, and allows it to expand to fill any remaining space in the parent view. Default weight is zero

calculation to assign any Remaining/Extra space between child. (not the total space)

space assign to child = (child individual weight) / (sum of weight of every child in Linear Layout)

Example (1): if there are three text boxes and two of them declare a weight of 1, while the third one is given no weight (0), then Remaining/Extra space assign to

1st text box = 1/(1+1+0) 
2nd text box = 1/(1+1+0) 
3rd text box = 0/(1+1+0)

Example (2) : let's say we have a text label and two text edit elements in a horizontal row. The label has no layout_weight specified, so it takes up the minimum space required to render. If the layout_weight of each of the two text edit elements is set to 1, the remaining width in the parent layout will be split equally between them (because we claim they are equally important).

calculation : 
1st label = 0/(0+1+1) 
2nd text box = 1/(0+1+1) 
3rd text box = 1/(0+1+1)

If the first one text box has a layout_weight of 1 and the second text box has a layout_weight of 2, then one third of the remaining space will be given to the first, and two thirds to the second (because we claim the second one is more important).

calculation : 
1st label = 0/(0+1+2) 
2nd text box = 1/(0+1+2) 
3rd text box = 2/(0+1+2)

In the width field of button, replace wrap-content with 0dp.
Use layout_weight attribute of a view.

android:layout_width="0dp"

This is how your code will look like:

<LinearLayout
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:orientation="horizontal">

 <Button
    android:text="Register"
    android:id="@+id/register"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:padding="10dip"
    android:layout_weight="1" />

 <Button
    android:text="Not this time"
    android:id="@+id/cancel"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:padding="10dip"
    android:layout_weight="1" />    

</LinearLayout>

layout_weight is used to distribute the whatever left space into proportions. In this case, the two buttons are taking "0dp" width. So, the remaining space will be divided into 1:1 proportion among them, i.e. the space will be divided equally between the Button Views.

Like answer of @Manoj Seelan

Replace android:layout_weight With android:weight.

When you use Weight with LinearLayout. you must add weightSum in LinearLayout and according to orientation of your LinearLayout you must setting 0dp for Width/Height to all LinearLayout`s Children views

Example :

If The orientation of Linearlayout is Vertical , then Set Width of all LinearLayout`s Children views with 0dp

 <LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical"
     android:weightSum="3">

     <Button
        android:text="Register"
        android:id="@+id/register"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:padding="10dip"
        android:layout_weight="2" />

     <Button
        android:text="Not this time"
        android:id="@+id/cancel"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:padding="10dip"
        android:layout_weight="1" />

  </LinearLayout>

If the orientation Linearlayout of is horizontal , then Set Height of all LinearLayout`s Children views with 0dp.

 <LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="horizontal"
     android:weightSum="3">

     <Button
        android:text="Register"
        android:id="@+id/register"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:padding="10dip"
        android:layout_weight="2" />

     <Button
        android:text="Not this time"
        android:id="@+id/cancel"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:padding="10dip"
        android:layout_weight="1" />

  </LinearLayout>

Perhaps setting both of the buttons layout_width properties to "fill_parent" will do the trick.

I just tested this code and it works in the emulator:

<LinearLayout android:layout_width="fill_parent"
          android:layout_height="wrap_content">

    <Button android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="hello world"/>

    <Button android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="goodbye world"/>

</LinearLayout>

Be sure to set layout_width to "fill_parent" on both buttons.

<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/logonFormButtons"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:baselineAligned="true"       
        android:orientation="horizontal">

        <Button
            android:id="@+id/logonFormBTLogon"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"            
            android:text="@string/logon"
            android:layout_weight="0.5" />

        <Button
            android:id="@+id/logonFormBTCancel"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"            
            android:text="@string/cancel"
            android:layout_weight="0.5" />
    </LinearLayout>

Below are the changes (Marked in BOLD) in your code:

<LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="horizontal">

     <Button
        android:text="Register"
        android:id="@+id/register"
        android:layout_width="0dp" //changes made here
        android:layout_height="wrap_content"
        android:padding="10dip"
        android:layout_weight="1" /> //changes made here

     <Button
        android:text="Not this time"
        android:id="@+id/cancel"
        android:layout_width="0dp" //changes made here
        android:layout_height="wrap_content"
        android:padding="10dip"
        android:layout_weight="1" /> //changes made here

  </LinearLayout>

Since your LinearLayout has orientation as horizontal, therefore you will need to keep your width only as 0dp. for using weights in that direction . (If your orientation was vertical, you would have kept your height only 0dp).

Since there are 2 views and you have placed android:layout_weight="1" for both the views, it means it will divide the two views equally in horizontal direction (or by width).

In the above XML, set the android:layout_weight of the linear layout as 2: android:layout_weight="2"

Plus you need to add this android:layout_width="0dp" for children views [Button views] of LinerLayout

You have to write like this its Working for me

<LinearLayout
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:orientation="horizontal"
            android:weightSum="2">

         <Button
            android:text="Register"
            android:id="@+id/register"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dip"
            android:layout_weight="1" />

         <Button
            android:text="Not this time"
            android:id="@+id/cancel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dip"
            android:layout_weight="1" />

 <LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="Button 1" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="3"
        android:text="Button 2" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="Button 3" />

    </LinearLayout>

This is perfect answer of your problem

  <LinearLayout 
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
        android:orientation="horizontal"  >   
     <Button 
        android:text="Register" android:id="@+id/register"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:padding="10dip" weight="1" />
     <Button 
        android:text="Not this time" android:id="@+id/cancel"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:padding="10dip" weight="1" />
  </LinearLayout>

Substitute wrap_content with fill_parent.

 <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_gravity="center"
            android:background="#008">

            <RelativeLayout
                android:id="@+id/paneltamrin"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"

                >
                <Button
                    android:id="@+id/BtnT1"
                    android:layout_width="wrap_content"
                    android:layout_height="150dp"
                    android:drawableTop="@android:drawable/ic_menu_edit"
                    android:drawablePadding="6dp"
                    android:padding="15dp"
                    android:text="AndroidDhina"
                    android:textColor="#000"
                    android:textStyle="bold" />
            </RelativeLayout>

            <RelativeLayout
                android:id="@+id/paneltamrin2"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                >
                <Button
                    android:layout_width="wrap_content"
                    android:layout_height="150dp"
                     android:drawableTop="@android:drawable/ic_menu_edit"
                    android:drawablePadding="6dp"
                    android:padding="15dp"
                    android:text="AndroidDhina"
                    android:textColor="#000"
                    android:textStyle="bold" />

            </RelativeLayout>
        </LinearLayout>

Linear Layout and weight in Android

Here is some examples

Horizontal orientation with equal weights

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivity">


    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="1" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="2" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="3" />

</LinearLayout>

Linear Layout and weight in Android

Horizontal orientation with unequal weights

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivity">


    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="1" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="2"
        android:text="2" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="3" />

</LinearLayout>

Linear Layout and weight in Android

Vertical orientation with equal weights

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

    <Button
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="1" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_margin="8dp"
        android:layout_weight="1"
        android:text="3" />

</LinearLayout>

Linear Layout and weight in Android