Develop Reference

What is the ButtonBarLayout and how should we use it?

When I developed, I found a new widget called android.support.v7.widget.ButtonBarLayout unexpectedly. I tried to search it on the internet, but nothing was found, even on the official development documents site.
In the meantime, I found two ButtonBarLayout when I search ButtonBarLayout everywhere in Android Studio, one is android.support.v7.widget.ButtonBarLayout and the other is com.android.internal.widget.ButtonBarLayout. I tried to read source codes of both, I found that they are the same except package name. So I thought maybe android.support.v7.widget.ButtonBarLayout came from com.android.internal.widget.ButtonBarLayout after the internal ButtonBarLayout was through tests and released. At the same time, ButtonBarLayout is inherited from LinearLayout.
But there are some question:
What can we get from ButtonBarLayout literally and how should we use it?
I noticed the variable of private boolean mAllowStacking. When it changes, orientation of this layout would be changed. But I didn't really understand what it is used for.
So does somebody know ButtonBarLayout well?
P.S.: I used Android Studio of 2.0.0 Preview 4 and Gradle Plugin of 2.0.0-alpha3 and Android Support Library of 23.1.1 and Platform-tools of 23.1 and Build-tools of 23.0.2.

As others pointed out, the class description tells exactly what it is: an extension of LinearLayout that automatically switches to vertical orientation when it can't fit its child views horizontally.
I might add that this was clearly done to fit with the material design specifications about dialogs. They make a distinction between side by side buttons and stacked buttons. See for example:
Side-by-side buttons are recommended when the text of each label does
not exceed the maximum button width, such as the commonly used
OK/Cancel buttons.
While you should go for stacked buttons when the single button is too large, or there's not enough room for both:
When text labels exceed the maximum button width, use stacked buttons
to accommodate the text. Affirmative actions are stacked above
dismissive actions.
So, one possible use of this class, is when designing your own dialogs. For example, AlertDialog and AlertDialog.Builder offer internal support for dialogs with buttons, but sometimes you just want to subclass DialogFragment or AppCompatDialogFragment for a better control.
There, it might be useful to setup a bottom button bar that follows the design guidelines, and have full control on the buttons (like enabling and disabling, things you can't do with an AlertDialog AFAIK).

The source code describes ButtonBarLayout as follows:
/**
* An extension of LinearLayout that automatically switches to vertical
* orientation when it can't fit its child views horizontally.
*/
So, in essence, it is nothing but a smart LinearLayout which manages auto-switching orientations based on available space on screen.
The same ButtonBarLayout.java file describes mAllowStacking in comments as follows:
/** Whether the current configuration allows stacking. */
Source Code Here

You are right first of all. ButtonBar layout does not seem to be featured anywhere in the official Android documentation. I tried myself to search about it, but to no avail. However I have found some information which defines what is a ButtonBar layout and when to use it. Hopefully this will help you.
Most tutorials use the Buttonbar layout in a dialogbox or at the bottom of a screen to confirm or decline an option. The image below is a visual representation of how the ButtonBar layout has been used in a screen.
The screenshot above has the following layout xml:
<LinearLayout
style="?android:attr/buttonBarStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="#+id/Button01"
style="?android:attr/buttonBarButtonStyle"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Show" />
<Button
android:id="#+id/Button02"
style="?android:attr/buttonBarButtonStyle"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Change" />
</LinearLayout>
<EditText
android:id="#+id/myView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >
<requestFocus />
</EditText>
So essentially what Android is doing here is simply creating two buttons next to each other in a LinearLayout with each button having the match_parent parameter set to the width. Hence each button takes half the size of the screen. Android have actually taken away the hassle of creating seperate buttons and positioning them correctly to fit different screens, by creating a simple widget handling this altogether.
As with the support library, Android have implemented this for developers using an earlier API. It is normal for them to use the support library for this purpose.
Hope this helps :)

https://android.googlesource.com/platform/frameworks/base/+/master/core/java/com/android/internal/widget/ButtonBarLayout.java
Looking into the code, I think it's a LinearLayout for buttons (duh). You can probably look at it like the Dialog buttons divided by a vertical spacer: | . AllowStacking will change the orientation to vertical and the gravity to the right instead of bottom. I should try it out to give a better answer

ButtonBarlayout is not featured anywhere in the official Android documentation.
it is used for auto-switching orientations according to the space.

Regarding your question:
How should we use it?
I guess it is undocumented because it is not stable yet.
It just popped up because this long lasting complaint originate from poor ROM modification by device vendor.
https://code.google.com/p/android/issues/detail?id=78377
See #270 for the resolution regarding classpath and why all classes inside .internal. were made public.
And nope even that fix a lot of bugs from poor ROM modification are still out there (in lots of device of well known brands). The issue is soon declined by project member.
I don't think we should use it just yet until the document show up.
Just my $.02 though.

Just to add to the other answers, if you guys want to check the orientation of a ButtonBarLayout you should check the orienation AFTER the value has called on measure.
In other words (Kotlin):
buttonBarLayout.post {
val orientation = buttonBarLayout.orientation
val height = buttonBarLayout.measuredHeight
}

Android 5.0 makes unselected checkboxes invisible when background is white

I have an android app that has been working fine pre-Android 5.0. With the update, I noticed that checkboxes and radiobuttons placed on white backgrounds are not visible if they are not selected. For example, this is what a checkbox looks selected and unselected in jellybean:
As you can see, there is a light gray square when the checkbox is not selected. However, after updating to lollipop, this is what it looks like:
So, as you can see, there is no gray square or anything that suggests there is a checkbox here. The same problem happens with radiobuttons. I really don't want to go trough the pain of creating new drawables just for this simple ting. I have seen that checkboxes within the accessibility menu of android 5 have a nice square, but haven't figured out how to make mine look the same:
I tried creating a new android project and just adding some checkboxes and radio buttons with a white background, but they are still invisible when unchecked. I'm using xamarin studio and c#, if that makes any difference. Anyway, I'll understand any java code you post.
This is what my checkbox code looks like:
<CheckBox
android:layout_width="wrap_content"
android:layout_height="0dp"
android:id="#+id/chkSeleccionar"
android:layout_gravity="right"
android:gravity="center_vertical"
android:clickable="false"
android:focusable="false"
android:scaleX="1.5"
android:scaleY="1.3"
android:layout_weight="50"
/>

I couldn't get the theme working, but what did work for me was the following:
android:button="#drawable/abc_btn_check_material"
android:buttonTint="#color/red"
Put this into your CheckBox XML layout.

Just change the
android:buttonTint="YOUR COLOR"
It works.

Make sure you are using a Material theme for Android 5.0 devices - this will ensure you're styling remains consistent with other components. Look for an android:theme element in your AndroidManifest.xml file (either on your application or on an individual activity), then look up what style is set there and check the parent attribute for the style.

Add this attribute
android:buttonTint="#EEEEEE"

Android xml design issues in version 4.1.2

I am working with android tablet's. which has now design issues in various version of android which is looking good in some version's and not looking good in some version's(xml layout designs).
i deployed my app in two different version(4.1.2 and 4.4.2) with same screen size 10 inch
But the result is not same since the design is somehow changed, Checkbox text is not aligned properly in 4.1.2 but 4.4.2 looks better as i expected..
What is the problem in my coding? i have attached the screenshot below and see the checkbox coding for the reference.
<CheckBox
android:id="#+id/rememberme"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="10dp"
android:paddingLeft="20dp"
android:button="#drawable/checkboxstate"
android:layout_marginRight="50dp"
android:paddingTop="10dp"
android:text="Remember me "
android:textColor="#000000" />
Helps Appreciated.!

Checkbox padding behaves differently before/after API 17. See this answer for a quick example of how to work around this. The same question contains more discussion of the underlying cause if you are interested.

textview doesn't go multiline

Here's my XML layout example of one of my TextViews which show itself correctly in android 4.2 ... I've downgraded a Nexus S to gingerbread 2.3.6 to test out my application and debug it! Right now, each of my TextViews doesn't take any more space than one line, not even wrapping itself at the end of the first line. (On 4.2, the example below was taking 3 lines and was adding "..." at the end if there was some text missing!)
How can I make my textViews compatible with gingerbread? Thank you!
<TextView
android:id="#+id/TV_guideRow_subtitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/TV_guideRow_title"
android:layout_below="#+id/TV_guideRow_title"
android:text="blabla text that could go up to 3 lines"
android:textColor="#3BB9FF"
android:layout_alignParentRight="true"
android:layout_above="#+id/TV_guideRow_more"
android:layout_marginRight="8dp"
android:layout_marginBottom="3dp"
android:ellipsize="end"
android:maxLines="3"/>

You want:
android:inputType="text|textMultiLine"
Also, depending on the parent of that TextView, multiline may not render properly. Try manually setting the height to, say, 100dp and see if that works.

After some more investigation, I've found out that all my related textView problems were related to my custom theme, which was made for android 4.0+ (since Holo was used as the base theme)
I've set the APIs which doesn't have holo to use the "Light" theme and everything is showing up correctly without any further modification.

Android Layout Editor Freaks Out on Question Mark

This is strange, yet I see it all the time as I have lots of reasons to display just a simple question mark in this app.
When editing with the Eclipse graphical layout editor, everything is fine...until I tell a TextEdit or a Button to display just a question mark. Here's my code:
<?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="vertical"
>
<TextView
android:id="#+id/test_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/question_mark" />
</LinearLayout>
And the string is defined in res/values/strings.xml. The relevant line is:
<string name="question_mark">\u003f</string>
The error message I get is:
Missing styles. Is the correct theme chosen for this layout? Use the
Theme combo box above the layout to choose a different layout, or fix
the theme style references.
Couldn't find theme resource for the current theme
Change the text, and the error message goes away.
You can see that in my struggles, I'm even trying to use the unicode version of a question mark. And yes, \? doesn't work either.
Note that this only happens when the graphical layout editor is set to API 7 or greater.
Now the graphical layout editor displays the question mark properly, and the emulator and my phone display the question mark without any problems. I'm just annoyed with the error message taking up 1/4 of my screen for all my layouts (and obscuring other error messages that may crop up).
Any suggestions?

First, test this again on the ADT 21 release that shipped today.
If the problem continues, create a sample project that demonstrates the issue, and post it along with step-by-step instructions on the Android issue tracker.

Well, this is a really crappy hack, but it kind of works--if you stand on your head!
You can use the unicode \u00bf as in
<TextView
android:id="#+id/test_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="\u00bf" />
It's not a normal question mark, but it's close enough for a hack and gets that annoying error message out of your hair. And it might even increase the humor quotient of your app!
But PLEASE, if anyone out there has a real fix, post it!

Wow, I entered a bug report...[time marches on]...finally, I get a few emails as the Google team starts to look at it.
Today, I received some good news. It looks like the bug has been fixed (and they found a few related bugs, which have been fixed as well). The fix will be in the next release, Version 21.1 Preview 2. You can read the official details here.
Looking forward to it!