Proper way to Implement Dark Theme Android Java

Question

I am learning how to implement Dark Theme to application.
After reading documents from this, below are the requirements that I understand

1. make sure "Style" parent = <style name="AppTheme" parent="Theme.AppCompat.DayNight">
2. create a new colors for Dark Theme in side colors.xml file
3. if using "Switch" toggle, use AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES); and AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO); inside onCheckedChanged listener

Based on testing, calling AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES); will trigger recreate() to recreate the activity, result it will change the theme as expected, also the BLACK blinking thingy will appear.

After reading through this, it stated that I need to declare setTheme method before setContentView(R.layout.activity_main); so it will solve the BLACK thingy issue.

The Android Dev document does not mentioned anything about setTheme is required in OnCreate method after AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES); is used

1. If using only AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES); able to switch desire theme, what's the point of using setTheme again in onCreate method?
2. Is the BLACK blinking thing a bug? or is there a proper way to solve it?

~~~~~~~~~~~~~~~~~~~~~~~~~~~ UPDATE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Maybe my questions is confusing as well. To make it short, just wanted to know that why "setTheme" is needed to declared in `onCreate` when `AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)` already restarted the acitivy?

I'm so confused and spent more than a week to solve this, guidance or tips are much appreciated

Answer 1

The AppCompactDelegate some times recreates the activity that causes black blinking

Check This It Changes theme without black blinking

Create two themes or use default dark theme xml like this :

<!--  Dark theme  -->

<style name="DarkTheme" parent="Theme.AppCompat.Light.DarkActionBar">

<item name="colorPrimary">@color/darkColorPrimary</item>
<item name="colorPrimaryDark">@color/darkColorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
<item name="fontFamily">@font/roboto</item>
<item name="listBackground">@color/darkListBackground</item>
<item name="cardBackground">@color/darkCardBackground</item>
<item name="textColor">@color/darkCardTitle</item>
<item name="actionBarBackgroundColor">@color/darkColorPrimary</item>
<item name="actionBarTextColor">@color/darkCardTitle</item>
<item name="dialogTextColor">@color/darkDialogTitle</item>
<item name="dialogDateColor">@color/dialogDateColor</item>
</style>


<!--  Light theme  -->

<style name="LightTheme" parent="Theme.AppCompat.Light.DarkActionBar">

<item name="colorPrimary">@color/lightColorPrimary</item>
<item name="colorPrimaryDark">@color/lightColorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
<item name="fontFamily">@font/roboto</item>
<item name="listBackground">@color/lightListBackground</item>
<item name="cardBackground">@color/lightCardBackground</item>
<item name="textColor">@color/lightCardTitle</item>
<item name="actionBarBackgroundColor">@color/lightColorPrimary</item>
<item name="dialogTextColor">@color/lightDialogTitle</item>
<item name="dialogDateColor">@color/dialogDateColor</item>
</style>

Use Shared Prefrence to save themes type

SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putBoolean("NightMode", false);
        editor.apply();

Change App theme on Activity on create method using shared prefrence

 if (!darktheme) {
            setTheme(R.style.DarkTheme);
        } else {
            setTheme(R.style.LightTheme);
        }

For Brief Information get that project : https://github.com/yeshasmp/ToDo/tree/v1.0