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 :)

Why my TextView under an ImageView is not showing

I am writing an Android game. In the level selection activity's layout file, I want to layout the levels' buttons (They are actually ImageViews) like this:
x x x
x x x
And each level button has a TextView, with that level's name as the text, below it (Let's call these two views together as a "level choice"). I used a lot of LinearLayouts to do this. Here is the code for a level choice:
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:orientation="vertical"
android:gravity="center_horizontal"
android:layout_weight="1">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/angles"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/angles_level"
android:textSize="#dimen/level_text_size"/>
</LinearLayout>
As you can see, the two views' height and width are all wrap_content. But when I look at the designer, the text view doesn't show up.When I select the text view in the component tree, it shows where the text view is:
P.S. The picture isn't showing all six levels because I haven't made them yet.
As you can see, the text view is right at the bottom! When I select the ImageView, it shows that it is occupying all the space of its parent!
I don't know why this is happening, my image is certainly a square! Can you explain why this is happening and how do I fix it?
If you need my whole layout code, feel free to tell me in the comments.

For me, the best solution is to position and size it properly by code (where you have total control) instead of xml.
Anyway, i think your problem can be solved by setting ImageViews ScaleType
imageView1.setScaleType(ScaleType.FIT_START);
By XML:
android:scaleType="fit_start"
Hope this helps.

I use background color for textview when I'm studying the layout.
If you use wrap content in both dimension for TextView, that is invisible since you did not write any text inside it. wrap content means that the view take the minimum space. And no text means 0px; try to set ImageView and TextView with layout_weight 1 and layout_height 0dp. In this way both view take half of space of parent layout

Because right now, your LinearLayout doesn't know how to distribute the ratio of its children. And in fact, your imageview's wrap content already
consumes the whole space.
So, LinearLayout says "Sorry TextView, you have no space left".
Use layout_weight to both of the children.
I guess you want to have your picture twice the size of your text.
2:1
That is,
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:orientation="vertical"
android:gravity="center_horizontal"
android:layout_weight="1">
<ImageView
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight=2
android:src="#drawable/angles"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight=1
android:text="#string/angles_level"
android:textSize="#dimen/level_text_size"/>
</LinearLayout>

I just realized that I posted a question about ImageViews leaving out too much whitespace:
LinearLayout leaving out too much white space. Why?
I think this is the same as that problem. So I tried setting adjustViewBounds to true in the xml. And it works! Now the image view look like this:
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:src="#drawable/parallel_lines"/>

You can use relative layout
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/angles"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/angles_level"
android:textSize="#dimen/level_text_size"/>
</RelativeLayout>
or simple you can set background of textview to that image by putting this
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/angles_level"
android:background="#drawable/angles"
android:textSize="#dimen/level_text_size"/>

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" />

Aligning center relative to others

So it's possible to align the top, bottom, left, and right of one view with another so that their edges are flush with each other. However, I've been wondering if it's possible to align the centers of two views of different sizes. My situation occurs when I have an ImageView side by side with a TextView, like this: [ImageView] [TextView]. The ImageView is bit taller than the TextView and so what I do is add padding/margins to the bottom of TextView to get it align and look like the ImageView and TextView horizontal centers are aligned. Problem is, when this view is displayed on larger tablet screens, the padding and margins don't work out right and the TextView doesn't look aligned with the ImageView. I'm sure there is an easy fix to allow this to always work out, so could someone provide me with some insights? Thanks!

This is how I did for a listview row:
<?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="#FFFFFF"
android:padding="5dp"
android:gravity="center_vertical">
<TextView android:id="#+id/questionItemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="20sp"
android:textColor="#000000"
android:gravity="center_vertical"/>
<ImageView android:id="#+id/questionViewed"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/eye"
android:layout_marginLeft="5dp" />
<ImageView android:id="#+id/questionAnswered"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/check"
android:layout_marginLeft="5dp" />
</LinearLayout>

Use weightSum rather than padding in dips or pxs, that will make your layout look fine regardless of the size of the user's device.
or you could use gravity as well.
Or you can create a second xml file and insert that one into your res/xlarge file, the phone will pick which xml to read.

Android centering text in lists

Say I have a list of Strings with the elements:
"One",
"Two",
"Three",
"Four"
I want to center them in the middle of the screen but I want to do it in a way that the start of each word is next to each other.
Like this:
One
Two
Three
Four
Considering that the font probably has different length per character, how do I do this best in Android?

I'm not sure how your application is behaving and if a ListView is strictly required, but the effect you desire can be achieved using TableLayout and TableRows. The TableLayout will line up the elements in each column for each row as you have described.
Having said that, TableLayout does not support having lines between the rows or gridlines (although I have seem some clever hacks involving changing the background colour of the TableRow to black, and then changing the padding and background colour of the View objects in the TableRow to white to get a black divider line - but that doesn't always work depending on your View objects).
I'm in a similar pickle, and that was the first avenue I examined. It didn't have a solution for my situation, but this might work for you. And if you do find a way of lining up the text in a List, I'd love to hear about it.
EDIT:
I also feel it is worth mentioning (based on how the conversation is progressing) that you can also set row.setOnClickListener() and make an entire row clickable in a TableView. Once you wrap it in a ScrollView, it's pretty list-like.

you can set the gravity at the elements you want to be center and for detail
android:gravity="center_horizontal"

Wrap your ListView in a LinearLayout with layout_gravity="center_horizontal" or
nvm: that won't work obviously..
So wait.. You want a list, where each line is clickable for the whole width of the screen, and you want to justify all lines to left, and ALSO center all of the justified text without breaking justification?

It sounds like you want to place your items within a parent with layout_width="wrap_content" and center the whole parent.
Something like this, perhaps?
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView android:text="Content above..."
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<LinearLayout android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal">
<TextView android:text="One"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView android:text="Two"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView android:text="Three"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<TextView android:text="Content below..."
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Remember the difference between gravity and layout_gravity. The gravity attribute refers to the view's content. layout_gravity (and all other attributes prefixed with layout_) refers to the view's layout within its parent.
Edit: If you're looking to format ListView items similarly, try something like this as your list item layout with the ListView itself using layout_width="fill_parent" and layout_height="fill_parent":
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:minHeight="?android:attr/listPreferredItemHeight"
android:weightSum="2"
android:gravity="center">
<TextView android:id="#+id/text"
android:layout_weight="1"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
Change the content of the TextView with id text in each list item in the usual way. The minHeight setting pulled from the current theme will make sure it stays a good size for touch.
The uniform centering in this case is handled by a combination of the weightSum and gravity on the LinearLayout and the layout_weight on the TextView. The TextView's weight divided by its parent's weightSum will determine the percentage of horizontal space the LinearLayout will give it. In the example above it will get 1/2 the available horizontal space, but centered.
Since ListView never knows the content of list items that are not currently onscreen there is no way to have it measure the text of every item in your adapter to center the content perfectly. You will have to approximate it using a list item layout like the example above.