Develop Reference

Android Layout Weight distribution

I am doing the following course at udacity. It's about Android User Interface.
As a part of my course I used an XML visualizer.
http://labs.udacity.com/android-visualizer/#/android/linear-layout-weight
Now upon experimenting I entered the following code
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:src="#drawable/ocean"
android:layout_width="wrap_content"
android:layout_height="400dp"
android:scaleType="centerCrop"
android:layout_weight = "1"/>
<TextView
android:text="You're invited!"
android:layout_width="wrap_content"
android:layout_height="100dp"
android:textColor="#android:color/white"
android:textSize="54sp"
android:layout_weight = "1"
android:background="#009688" />
<TextView
android:text="Bonfire at the beach"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#android:color/white"
android:textSize="34sp"
android:background="#009688" />
</LinearLayout>
as per my understanding, by using android:layout_weight the whole parent layout is divided as per priority and distributed accordingly, if so, the space after distributing among image and "You're invited!" there should only be remaining space enough, to fill out "Bonfire at the beach".
Then why there is a empty space below "Bonfire at the beach" ?
(Also if possible can anyone please explain how the control flows among XML code).
UPDATE
when I added android:layout_weight = "0" in "Bonfire at the beach" then there is no empty space below. Can any one explain why this happens and why there is space in previous case. and this is the code is used.
before
after
even tried setting height to 0dp

Understand it using the below example
Weight defines how much space a view will consume compared to other views within a LinearLayout.
Weight is used when you want to give specific screen space to one component compared to other.
Key Properties:
weightSum is the overall sum of weights of all child views. If you don't specify the weightSum, the system will calculate the sum of all the weights on its own.
layout_weight specifies the amount of space out of the total weight sum
the widget will occupy.
Code:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:weightSum="4">
<EditText
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Type Your Text Here" />
<Button
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Text1" />
<Button
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Text1" />
</LinearLayout>
The output is:
Now even if the size of the device is larger, the EditText will take 2/4 of the screen's space. Hence the look of your app is seen consistent across all screens.
[This if before you edit your question might be irrelevant now
Now in your Bonfire at the beach there is no weight and its wrap_content so there is no grantee that it will take the remaining space! and that space can remain after adding it will differ with the screen size of device ]
Note:
Here the layout_width is kept 0dp as the widget space is divided horizontally. If the widgets are to be aligned vertically layout_height will be set to 0dp.
This is done to increase the efficiency of the code because at runtime the system won't attempt to calculate the width or height respectively as this is managed by the weight. If you instead used wrap_content the system would attempt to calculate the width/height first before applying the weight attribute which causes another calculation cycle.
Lets Move to your XML
see how i used them
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:weightSum="3" //<-------------------
android:layout_height="match_parent">
<ImageView
android:src="#drawable/mc"
android:layout_width="match_parent"
android:layout_height="0dp"
android:scaleType="centerCrop"
android:layout_weight = "1"/> //<-------------------
<TextView
android:text="You're invited!"
android:layout_width="match_parent"
android:layout_height="0dp"
android:textColor="#android:color/white"
android:textSize="54sp"
android:layout_weight = "1" //<-------------------
android:background="#009688" />
<TextView
android:layout_weight = "1" //<------------------- if you remove this , this text view will be gone cuz its 0 by default
android:text="Bonfire at the beach"
android:layout_width="match_parent"
android:layout_height="0dp"
android:textColor="#android:color/white"
android:textSize="34sp"
android:background="#009688" />
</LinearLayout>
Now you ask what if you have not given android:layout_weight ,Default weight is zero. Zero means view will not be shown, that empty space will remain there
Since you don't believe you can read the documentation
EDIT: 2
Since you said that, i went through android-visualizer that you use
and Have you ever noticed this...
"Line 6: The attribute android:weight_sum is not supported here."
thing on its bottom.
Meaning they are not providing that functionality to adjust your layout boundaries. Its just a simple online tool.I am
not saying it is not recommended to use, but my personal idea is, you
can't touch the depth of android if you use that.
Now if you want a confirmation what actually happens have a look on android studio/ eclipse as well which are read IDE s
This is android studio
Can you see any view contain your text "Bonfire at the beach"? no
Instead a.studio display a red line in XML.
Suspicious size: this will make the view invisible
Because there is no layout_weight is given and we have added 0 height
Now you can accept the answer :)

match_parent not performing as expected

I imagine this should be a fairly easy one to answer, if you understand XML Layouts better than I do that is. I don't seem to get what I was thinking I should when using the match_parent layout_height.
I have a LinearLayout root element with android:orientation="vertical". Inside this LinearLayout I want three elements:
- TextView
- ListView
- TextView
For both the TextViews I set android:layout_height="wrap_content" so that they will be only as tall as is necessary to display their contents. The thing is, I want the one TextView to sit at the top of the form, the other one to sit at the bottom of the form while the ListView fills up whatever space is available on the form. So here is what my xml layout looks like:
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Top TextView" />
<ListView
android:id="#+id/listView_Species"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Bottom TextView" />
But it doesn't work. Here's what I get. I've selected the ListView so that it will be highlighted. Notice how it extends all the way to the bottom of the form, pushing the bottom TextView off the form.
When I change the layout_height property of the ListView to some fixed value, like 180dp, this is what the form looks like. I'm just posting this to prove that the bottom TextView is there but I still don't know how to get it to be fixed to the bottom of the screen while the ListView takes up whatever space remains, but in between the two TextViews.
Thanks in advance.

While the other answers try to fix your problem (which they don't actually--they suggest you do something that looks similar but may or may not look good on different devices), no one has filled in the gaps in your knowledge of LinearLayouts and match_parent. And these gaps are very common--Google's documentation is still far below stellar.
First, how do Views work within a LinearLayout? Let's go through the process of drawing a LinearLayout, using orientation="vertical" for simplicity.
Examine the height of the first child of the LinearLayout (LL for short). If the height is match_parent or fill_parent (old name for the same thing) then the height of the View is stretched to fill the entire viewing area. If the height is wrap_content, then measure the vertical space the View takes and use that space for the View. If the height is a non-zero number, use exactly that many pixels for the View's height (may clip if too small). If the height is 0 see below.
Put the next view below the view in 1. Check its height and act accordingly.
Continue for all the Views. If a View is pushed off the bottom, go ahead and stop calculating because no one will see it or any succeeding Views (assuming no ScrollView).
If the height of a View is 0, check it's gravity. This requires a second pass, storing the gravity of all the views and then allocating their heights proportionally. As you can guess, the second pass doubles the time layout takes, which isn't significant for simple layouts.
Explanation of your example: The first child of the LL (the first TextView) is measured and takes a certain amount of pixels. Then your ListView takes all the remaining space (via match_parent). And then your second TextView is not drawn at all as it's off the bottom of the screen. Which is pretty much what you observed, but now you understand why.
Solution: Use RelativeLayout. Works perfectly in this case.
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/top_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:textSize="30sp"
android:text="Top TextView" />
<TextView
android:id="#+id/bottom_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:textSize="30sp"
android:text="Bottom TextView" />
<ListView
android:id="#+id/listView_Species"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/top_tv"
android:layout_above="#id/bottom_tv"
/>
</RelativeLayout>
The RelativeLayout tells the layout inflater to draw the first TextView at the top, then draw the second TextView at the bottom, and then fill the rest of the space with your ListView. I believe this is exactly what you want.
Welcome to Android. You'll be using this pattern a LOT!

Change the ListView height to 0dp and add weight=1
i.e.:
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Top TextView" />
<ListView
android:id="#+id/listView_Species"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Bottom TextView" />

use android:layout_weight to define weights to your widgets inside the outermost layout. Declare their height as 0dp and then define android:layout_weight to each one of them .
Total weigh sum of the three of them should be 1. According to your need you can deine 0.1 weight to both top and bottom TextView's and define 0.8 to ListView.
<TextView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight = "0.1"
android:textSize="30sp"
android:text="Top TextView" />
<ListView
android:id="#+id/listView_Species"
android:layout_width="match_parent"
android:layout_weight = "0.8"
android:layout_height="0dp" />
<TextView
android:layout_width="match_parent"
android:layout_height="0dp"
android:textSize="30sp"
android:layout_weight = "0.1"
android:text="Bottom TextView" />

correct way to display EditText

I'm confused and frustrated that I can't get my EditText field to take up a rational amount of space in the layout without explicitly telling it how many pixels to be.
I'm *sure I'm missing something obvious, but my experience is that EditText totally ignores layout_weight and either grows/shrinks dynamically with the text that is entered into it if I give it a layout_weight of "wrap_content" or takes up most of the space in its parent layout if I give it a weight of fill_parent.
So... what is the correct path to having an EditText field that occupies some portion of its parent layout (in my case Linear, but I'm flexible) so that it can have a label next to it and look like:
Name: [ EDIT TEXT HERE ]
Phone:[ EDIT TEXT HERE ]
etc.
TIA

You can do a couple different things. As mentioned, you should be using dp instead of pixels for layout. Using dp allows your views to scale by the screen's physical size rather than resolution.
Here's an example of specifying the edit boxes to appear to the right of each label and take up the remainder of a the screen:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="#+id/name_label"
android:layout_width="100dp"
android:layout_height="50dp"
android:text="Name:" />
<TextView
android:id="#+id/phone_label"
android:layout_width="100dp"
android:layout_height="50dp"
android:layout_below="#id/name_label"
android:text="Phone:" />
<EditText
android:id="#+id/name_text"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_toRightOf="#id/name_label" />
<EditText
android:id="#+id/phone_text"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_toRightOf="#id/phone_label"
android:layout_below="#id/name_text" />
</RelativeLayout>
Here's an example of a LinearLayout where weight is used:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_height="match_parent"
android:text="Name:"
android:layout_weight="1"/>
<EditText
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="5"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_height="match_parent"
android:text="Phone:"
android:layout_weight="1"/>
<EditText
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="5"/>
</LinearLayout>
</LinearLayout>
Note that the LinearLayout has 7 views while the RelativeLayout accomplishes something similar with 5 views. LinearLayouts hare handy, but they're more complex. As your layouts get more complicated, they will perform worse than RelativeLayouts, especially when you nest them.

For each line use a horizontal LinearLayout.
Inside that, add a horizontal LinearLayout to 'wrap' the TextView. Give that LinearLayout a layout_weight of 20 (for example).
Use another horizontal LinearLayout to 'wrap' the EditText and set the EditText to fill_parent but give its outer LinearLayout a layout_weight of 80 (or whatever value based on 20+80 = 100% if you see what I mean).
EDIT: Also if you need to have multiple lines then to simplify the overall layout file, you can define a 'single line' layout file and use it as a custom layout entry.

//for your edittext set min width and max length
android:minWidth="40"
android:maxLength="30"
android:layout_width="wrap_content"
so that it will be always shows minimum width and your characters wont exceed more than 30.

You need to work with the Layout. LinearLayout is not the right Layout for your purposes. Have a look at TableLayout, which I think might fulfill your requirements. Have a look at the TableLayout tutorial.

android layout dynamic sizing

For many "header" TextViews across the pages I'm designing for a program, I would like them to be the parent.Width / 2 then properly aligned. While that would be fairly easy to code in the Java, I am attempting to do as much as possible in the XML layouts to avoid XML-Java code intersections until the last little bits (button presses, finish page, etc).
Do I have to go through each page and calculate every item's specific width myself or is there a way to put something along the lines of "fill_parent / 2"?
EDIT: Forgot to mention what is likely a key note - almost everything I am doing is in RelativeLayouts, I have very little use for LinearLayouts in this project.

If you have a LinearLayout that is flush to the left and right, you can do the following:
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:weightSum="2"
android:gravity="left"
android:orientation="horizontal">
<TextView
android:layout_weight="1"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:text="I take up half the width!!!1" />
</LinearLayout>
By setting the weightSum on the parent, you're saying that the weights of the children should equal that amount. By setting the single child's weight to half of that, it'll take up half the space. Make sure to set the width of the child to 0 so it knows to use the weight value to calculate its space relative to its parent.
Then, you can align it however you'd like by setting gravity on the parent LinearLayout.

Use a tableview with two columns where each column is stretched and has a text view. Then hide the second textview
<TableLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:stretchColumns="1">
<TableRow>
<TextView android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=" Set Item Name "/>
<TextView android:id="#+id/hiddenTextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:visibility="invisible"/>
</TableRow>
</TableLayout>

Scale layout items equally on large screens

I've got a 4-item start screen in my app, which looks like the following:
What's important to me there:
- All items do have the same width (not regarding how much text is actually in it)
- Look the same on all devices (small-screen, mdpi, large-screen, etc.)
Im just wondering if there is a easy solution about this problem?
I've tried using 3 LinearLayouts but thats really awkward..
(1 presenting the layout root[vertical] and two which do each contain 2 buttons[horizonal]).
Making this layout ready for multiple screens would require a lot of fixed-width and fixed-margin hacking. Just like "button margin = 30dp on xlarge, 20 on large, 15 on normal,...".
My layout-xml:
<?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="#drawable/background"
android:id="#+id/main_root"
android:orientation="vertical"
android:gravity="center" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_gravity="center" >
<Button
android:id="#+id/btn_learn"
android:text="#string/mainBtn_learn"
style="#style/mainBtn"
android:onClick="handleBtnClick"
android:layout_margin="20dip" />
<Button
android:id="#+id/btn_quiz"
android:text="#string/mainBtn_quiz"
style="#style/mainBtn"
android:onClick="handleBtnClick"
android:layout_margin="20dip" />
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_gravity="center" >
<Button
android:id="#+id/btn_search"
android:text="#string/mainBtn_search"
style="#style/mainBtn"
android:onClick="handleBtnClick"
android:layout_margin="20dip" />
<Button
android:id="#+id/btn_more"
android:text="#string/mainBtn_more"
style="#style/mainBtn"
android:onClick="handleBtnClick"
android:layout_margin="20dip" />
</LinearLayout>
Is there a view which "auto-scales" these Buttons or still any other easier solution?
Edit:
So, in special, you need something like
button:
android:layout_width="15%" // 15% of screen width / height depending on the orientation
android:layout_marginBottom="10%" // see above

I'm pretty new to Android development but I can show you what worked for me in a similar case. I defined my layout as follows:
<LinearLayout
android:id="#+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<EditText
android:id="#+id/outputText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:editable="false" />
<Spinner
android:id="#+id/outputSpinner"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:prompt="#string/OutputBaseOptionsPrompt" />
</LinearLayout>
I have a horizontal layout with two items. The LinearLayout has a width of "match_parent" so that it is as wide as the screen. Both items in the layout have the following:
android:layout_width="0dp"
android:layout_weight="1"
Since both items have a layout_weight of 1, they will be drawn at the same width. In this case, each item takes up half of the available space. If you change the weight of one of these items to "2" then it will be twice as wide as the item with a weight of "1".

Do you already have xml that makes it work on one screen size? If so post what you have so far.
I would suggest using a RelativeLayout for your root though. You can use the alignCenter attributes to float your children towards the middle. Then you just have to hard code the inner margins (how far apart you want the buttons) rather than the margin from yourself to the wall.
You could also avoid having to hard code the inner margin by making your own button 9 patch images. You can just add a border of transparent pixels in your image to represent the margin. You'll probably still want to supply an image for each density you wish to support though.

The solution is you dont use hardcoded values any where
Put three images with same name in hdpi mdpi and ldpi folders in drawables
an run the code