Develop Reference

Black screen on starting app

I have noticed that on android versions 6.0+,when someone starting app after login screen and submiting info,black screen appear and you have to wait 3-15 sec depending on devices.
I heard that it could be for heavy loadings,but this app is nothing special it just load listview with few images after login (i had 3 images while tested) so im not sure is it really that heavy plus it only happen on newer versions of android so im not sure what to do.
I can provide whole code or some snippet.
EDIT: I tried with various image sizes (full loaded with big images,and only 1 small image) and it have no effect at all.
Anyone???

Inside your manifest file .
In your Activity tag add this theme.
android:theme="#android:style/Theme.Translucent"
And then you need to extend your respective activity from Activity class.
It will work for sure

For those who face this error in future
<style name="FullscreenTheme" parent="MainTheme">
<item name="windowNoTitle">true</item>
<item name="windowActionBar">false</item>
<item name="android:windowFullscreen">true</item>
<item name="android:windowContentOverlay">#null</item>
<item name="android:windowIsTranslucent">true</item>
</style>

Android activity transition animation inconsistent

In my one activity page, there are many item.
One of items, use startActivity() go to an android system settings activity,
And its activity transition animation is slide_out_left.
The other items use startActivity() go to my own activity.
and activity transition animation is fade_out(defined in my style.xml).
I think that is a reason, but I don't know why?
Why my style.xml changed all activity transition animation except one.
or its there something I didn't notice?
And how can I consistent all activity transition animation in XML file?
(I know overridePendingTransition() can change the animation, but I want to modify in .xml file, not in java code, to stay my java code easy readable in the future.)

Please have a look at this answer and see whether it solves your issue or not: Start Activity with an animation
In short:
<style name="AppTheme">
<item name="android:windowAnimationStyle">#style/MyAnimation</item>
</style>
<style name="MyAnimation" parent="android:style/Animation.Activity">
<item name="android:activityOpenEnterAnimation">#anim/open_enter</item>
<item name="android:activityOpenExitAnimation">#anim/open_exit</item>
<item name="android:activityCloseEnterAnimation">#anim/close_enter</item>
<item name="android:activityCloseExitAnimation">#anim/close_exit</item>
</style>
If you think this answers your question, please go to that original link that put in the answer and give the original author credit :)

How to switch themes (night mode) without restarting the activity?

I have made a few apps that support multiple themes, but I always had to restart the app when user switches theme, because setTheme() needs to be called before setContentView().
I was okay with it, until I discovered this app. It can seamlessly switch between two themes, and with transitions/animations too!
Please give me some hints on how this was implemented (and animations too). Thanks!

#Alexander Hanssen's answer basically has answered this...
Don't know why it was not accepted... Maybe because of the finish()/startActivity().
I voted for it and I tried to comment but cannot...
Anyway, I would do exactly what he described in terms of styles.
<style name="AppThemeLight" parent="Theme.AppCompat.Light">
<!-- Customize your theme here. -->
<item name="android:windowAnimationStyle">#style/WindowAnimationTransition</item>
</style>
<style name="AppThemeDark" parent="Theme.AppCompat">
<!-- Customize your theme here. -->
<item name="android:windowAnimationStyle">#style/WindowAnimationTransition</item>
</style>
<!-- This will set the fade in animation on all your activities by default -->
<style name="WindowAnimationTransition">
<item name="android:windowEnterAnimation">#android:anim/fade_in</item>
<item name="android:windowExitAnimation">#android:anim/fade_out</item>
</style>
But instead of finish/start with new intent:
Intent intent = new Intent(this, <yourclass>.class);
startActivity(intent);
finish();
I would do:
#Override
protected void onCreate(Bundle savedInstanceState) {
// MUST do this before super call or setContentView(...)
// pick which theme DAY or NIGHT from settings
setTheme(someSettings.get(PREFFERED_THEME) ? R.style.AppThemeLight : R.style.AppThemeDark);
super.onCreate(savedInstanceState);
}
// Somewhere in your activity where the button switches the theme
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// decide which theme to use DAY or NIGHT and save it
someSettings.save(PREFFERED_THEME, isDay());
Activity.this.recreate();
}
});
The effect is as shown in the video...

The transition/animation makes the theme change seamless when you restart the activity, and this can be done by adding the items "android:windowanimationStyle" to your themes, and then referencing a style where you specifiy how the Activity should animate when it enters and exits.
Note that this makes the animation apply on all activities with that theme.
<style name="AppThemeLight" parent="Theme.AppCompat.Light">
<!-- Customize your theme here. -->
<item name="android:windowAnimationStyle">#style/WindowAnimationTransition</item>
</style>
<style name="AppThemeDark" parent="Theme.AppCompat">
<!-- Customize your theme here. -->
<item name="android:windowAnimationStyle">#style/WindowAnimationTransition</item>
</style>
<!-- This will set the fade in animation on all your activities by default -->
<style name="WindowAnimationTransition">
<item name="android:windowEnterAnimation">#android:anim/fade_in</item>
<item name="android:windowExitAnimation">#android:anim/fade_out</item>
</style>
Then, when you want to change theme you could do this when clicking a button:
AppSettings settings = AppSettings.getInstance(this);
settings.set(AppSettings.Key.USE_DARK_THEME,
!settings.getBoolean(AppSettings.Key.USE_DARK_THEME));
Intent intent = new Intent(this, <yourclass>.class);
startActivity(intent);
finish();
Then in your onCreate method, use the setTheme() to apply the theme that is currently set in AppSettings like this:
AppSettings settings = AppSettings.getInstance(this);
setTheme(settings.getBoolean(AppSettings.Key.USE_DARK_THEME) ? R.style.AppThemeDark : R.style.AppThemeLight);
super.onCreate(savedInstanceState);
setContentView(<yourlayouthere>);
Check out this gist for reference: https://gist.github.com/alphamu/f2469c28e17b24114fe5

for those who are trying to find solution for android version 10 or updated.
to set dark/light mode use this:
AppCompatDelegate.setDefaultNightMode(state) //state can be AppCompatDelegate.MODE_NIGHT_YES or AppCompatDelegate.MODE_NIGHT_NO
it will change the display of your app but with a flicker
to avoid the activity recreation flicker (for smooth transition), in your activity add the below method
#Override
public void recreate() {
finish();
overridePendingTransition(R.anim.anime_fade_in,
R.anim.anime_fade_out);
startActivity(getIntent());
overridePendingTransition(R.anim.anime_fade_in,
R.anim.anime_fade_out);
}

setTheme() before super.onCreate(savedInstanceState) in GKA answer is perfect approach and work well, thanks to GKA.
but it creates new instances for all resources again, including activities, fragments, and recycler views. I think it may be heavy work and cause to loss of some saved data like local variables.
accourding to google document: https://developer.android.com/reference/android/app/Activity#recreate()
Cause this Activity to be recreated with a new instance. This results
in essentially the same flow as when the Activity is created due to a
configuration change -- the current instance will go through its
lifecycle to onDestroy() and a new instance then created after it.
there is another approach that you can change the theme programmatically with code (Java or Kotlin), in this approach you don't need to recreate all resources, and also you can use custom animation like ripple.
check my GitHub library:
https://github.com/imandolatkia/Android-Animated-Theme-Manager
in this library, you can create your custom themes and change them dynamically with ripple animation without recreating any resources.

Simply efficient one liner in fragment:
requireActivity().recreate();
For activity:
recreate();

There isn't anything preventing you from calling setTheme() and then setContentView() again. You'll just need to restructure your app a bit so that, if you change the theme, you need to reinitialize any member variables you might have that are holding references to View objects.

Google Glass CardScrollView does not render while swiping

I'm attempting to create a GDK app that has a similar user interface as the sample Timer app in that it launches sub-activities in which to render CardScrollView instances that cycle through valid selections.
My problem is that once I am at the point where I cycle through the numbers, the CardScrollView stops rendering while the scrolling is in motion. I can see the previous activity revealed and rendering until the activity containing the currently active cards stop scrolling.
Is there something obvious I'm missing here?

In my case, the answer was that I'd foolishly applied the "MenuStyle" style that the Timer activity uses to all my sub-activities in the AndroidManifest. This style specifies the following:
<style name="MenuTheme" parent="#android:style/Theme.DeviceDefault">
<item name="android:windowBackground">#android:color/transparent</item>
<item name="android:colorBackgroundCacheHint">#null</item>
<item name="android:windowIsTranslucent">true</item>
<item name="android:windowAnimationStyle">#null</item>
</style>
So indeed, given the null animation style and the transparent background, nothing would be displayed while the CardScrollView is in motion.

How to remove white screen before loading of first activity in android?

Whenever i launch my app, a white screen appears in the beginning with the title bar. I don't want this screen to be appear in my app. I have read previous questions, but answers are not clear to me.
I'm also using splash screen, but white screen appears before that.
I don't want to change the theme style, because it either increases the minimum sdkVersion or changes the style of edittext, buttons, checkboxes etc
Please help me to keep me out of this.
Thank you.

Preface: For questions like this you should post your starting activities xml and the onCreate() and associated methods.
When android starts your application it will typically use a black view to indicate that it is launching, this my change to white with your theme/style selected. If you are loading the view correctly then you should only see this blank (white or black) page for 50-200 ms (I can't find the google document for this right now). If you are doing a lot of work in your onCreate method then it will take longer.
Typically to make my views display faster I will simply do the majority of the linking work after it has loaded. ex:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.initial_activity_layout);
//We use a handler so that the activity starts very fast
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
delayedInit();
}
}, 100);
}
Additionally, mobile applications should typically not have a splash screen unless they take quite a while to load the contents (e.g. games, first time launch files, etc.) and should not be used just to brand your application, or display your company name.
Update (July 31, 2015)
Google apps are now moving in the direction of having splash screens (see drive, GMail, etc.)
Additionally, You shouldn't be doing any work other than de-referencing views in the onCreate() method. Any long running operations such as retrieving information from memory (database, prefs, etc.) should be done in an AsyncTaskLoader or AsyncTask.

If you are using AppCompatActivity then create below theme in style.xml :
<style name="Theme.Transparent" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:windowNoTitle">true</item>
<item name="android:windowActionBar">false</item>
<item name="android:windowFullscreen">true</item>
<item name="android:windowContentOverlay">#null</item>
<item name="android:windowIsTranslucent">true</item>
</style>
And in manifest file for SplashActivity add theme :
android:theme="#style/Theme.Transparent"

Add below line in your Theme of splash screen as you wrote you are using splash screen
<item name="android:windowFullscreen">true</item>
<item name="android:windowContentOverlay">#null</item>
<item name="android:windowIsTranslucent">true</item>

1- Make windowDisablePreview false in your style.xml
<item name="android:windowDisablePreview">false</item>
2- Add windowBackground in your style.xml.
<item name="android:windowBackground">#drawable/your_background</item>