Fix slidebars going out of bounds and twitching + fix dialog in demo app

[Ultron55]

Fix Slidebars

• for selector.setX :
  selector.getMeasuredWidth() -> selector.getWidth() / 2f

• return if out of range:

  if (event.getX() > getWidth() || event.getX() < 0) {return false;}

fix dialog in demo app - indexes were mixed up

[Ultron55]

Would you please run ./gradlew spotlessApply before merging this?

I haven't used a similar one before. Do not tell me why when executing the command./gradlew spotlessApply I get an exception:

Task :app:spotlessJava FAILED Step 'removeUnusedImports' found problem in 'src\main\java\com\skydoves\colorpickerviewdemo\MainActivity.java': null java.lang.reflect.InvocationTargetException... Caused by: java.lang.IllegalAccessError: class com.google.googlejavaformat.java.RemoveUnusedImports (in unnamed module @0x716ea415) cannot access class com.sun.tools.javac.util.Context (in module jdk.compil er) because module jdk.compiler does not export com.sun.tools.javac.util to unnamed module @0x716ea415

and

Step 'removeUnusedImports' found problem in 'src\main\java\com\skydoves\colorpickerview\ActionMode.java': null

The SDK in the settings has chosen the same as the project - 11