boober | Controller to create and update OpenShift objects | Cloud library

I am trying to reconcile the following two things:

A) I want a precise, uniform, and clean UI with several identically sized buttons that correspond exactly to the underlying 'grid cells' -- A UI that will look as similar as possible (proportionally to screen size) across as many Android devices as possible.

B) On Android, the screen dimensions (aspect ratio and actual pixel numbers) of the user's device are unknown (to the app) until runtime.

My solution to this was to: (there is a code example below!)

1) Lock the app to portrait mode,

2) Do not define anything in static/absolute terms like dp,px, etc. and instead conceptualize a 'basic unit of measure' that is a function of screen height -- 0.08% in my case -- and base everything off of that.

3) Set horizontal guidelines within a ConstraintLayout whose positions are expressed as a percentage of parent (screen) height.

4) Make all buttons use this 'basic unit' as their height and width by setting their XML layout_constraintDimensionRatio attribute to "1:1" and using the guidelines above (see step 3),

5) Accomplish positioning and dimensions of all views by using constraints to either these guidelines, the parent's bounds, or one additional vertical guideline at 50% of screen width.

The problem is that depending on the pixel height of the screen (whether it happens to be odd or even... or maybe other factors), the dimensions of a view/button, (and thus the paths drawn inside it) constrained between one pair of guidelines does not exactly match those of another view drawn between some other pair... even though the distance between both pairs of guidelines should be the same percentage of parent height. :)

Here is an example showing the Nexus 4 emulator:

At first I thought the problem was simply due to rounding 'error' during Android's dimension calculations, but then why would the view not be square even though they are prescribed the 1:1 ratio attribute?

The only solutions I can think of would be:

A) To do the layout programatically instead of with XML... and set the guideline positions as exact pixel locations instead of percentages, and answer the question, "what is 0.08 x screen height?" myself... making the appropriate corrections to compensate for 'indivisible' screen heights.

B) Override onLayout() in the custom views and "force" their dimensions to be consistent... but then this would defeat the purpose of guidelines. :(

But I'm really hoping there is an easier solution than A or B.

(I know someone is going to suggest GridLayout, but it's not an option, for a few reasons... one of which is that in GridLayout, views inside cells must be set to wrap_content... which means the paths they draw cannot be generated relative to parent at runtime).

Thanks for any other suggestions, though.

Code Example:

I whipped up a simple 'minimal example' below that should be easy to reconstruct in Android Studio. The logs will reveal the issue if it's not immediately apparent.

XML layout:

I'm working on a very small Android Project that uses this exact code from github.

However, when I (or you) intermittently button mash the start/stop button... the app eventually crashes. Unfortunately this can take a little while to reproduce... but it will happen!

Oh, I forgot the desired result!!

The desired result is that this crash does not occur. :)

Does anyone know why this crash occurs? The author of this code has had an open bug/issue for this on Github since March of 2013... so I'm pretty sure it's not a particularly stupid question... and if you do know the answer to this, you would no doubt be a hailed as a bowss.

I have been dissecting the code, print debugging, and researching ASyncTask, Handlers, and AudioTrack for a couple of days now but I can't figure it out... I will though if nobody else beats me to it.

This is the stack trace:

In my app, I would like to have a simple method that uses the MediaPlayer class to play a sound resource once (and again, if needed).

I have successfully achieved this (see code below) and successfully tested it on a real hardware device with API 23, and also on emulators with API levels from 19 all the way to P... EXCEPT FOR API 21, WHERE IT FAILS.

Isn't that weird? Why would something work on API 19... and 23, but not 21?

So what do I mean by fail? Well, on API 21, if you press the play button, no sound plays, and nothing appears to happen (although if you peek at the logcat, ye shall behold all manner of scary native library messages including many "deaths" and even "tombstone" or two).

If you continue to press play a second time, the same thing happens, with more internal error messages being generated in logcat... and the third time, you finally get a crash.

The only error I can see that could be related to anything I have control over is the Exception that's caught in Log.i:

"com.example.boober.stackqmediaplayer I/SFX: error:java.io.IOException: Prepare failed.: status=0x64"

All the other messages and final stack trace are all generated by internal native libraries.

I've googled these errors, read the logcat and MediaPlayer documentation. Hopefully I'm just doing something fundamentally stupid that someone can point out to me.

I was really hoping maybe someone out there can take a look.

I've whittled up a very minimal example of the problem that should be very easy to cut/paste/rebuild in Android Studio so you can reproduce the problem:

MainActivity:

I'm having a bit of a problem with ConstraintLayout in Android.

Observe the following illustration:

I would like to draw your attention to the row of three views across the middle: the TextView, and the two Buttons.

The dotted vertical and horizontal lines are fixed guidelines (expressed in terms of percentage of screen height/width), and are used to constrain these views to.

The TextView is constrained in all 4 directions as you can see.

The Button on the far right is constrained in 3 directions: top, bottom, and right... and has an aspect ratio constraint on it of 1:1.

Now, the Button in the middle is only constrained on top and bottom, and also has an aspect ratio applied of 1:1.

Everything is great so far... but what if we want to keep everything exactly the same except center the middle button such that it has equal space to its right and to its left?

One might expect that simply applying horizontal constraints to its nearest neighbors would do the trick... but no.

This is the result:

So... the size of the button is increasing for some reason. Why?

It seems to me that Android Studio is applying the 1:1 aspect ratio rule (in this case) by saying "height is a function of width..." that is, width is calculated first (based on the newly applied constraints) and therefore takes precedence.

If it had simply done it the other way around and said "width = height" with height taking precedence... (the same way it was doing prior to those final constraints being applied), then everything would be fine.

So... in other words, how can you center a "middle" view between two other "right" and "left" views and still maintain:

1) All three views have matching heights since they are bound by the same horizontal constraints.

2) The left view is in a fixed position.

3) The right view has a 1:1 aspect ratio and is not allowed to separate from its right-side guideline (fixed position).

?

EDIT: I have made the following XML snippet for anyone that wants to play with it:

(Remember the three rules above. Have fun!)