Android Get the next or previous Enum

Question

I need a way to get the next/previous enum.
My problem is that I cannot iterate the normal way:

for( Mode m: Mode.values() ) {
    . . .
}

I need to get the next enum inside a method, each time it is called:
Note that Mode is a system Enum, therefore I cannot define methods, unless I create my own Enum, which is a solution, but a less preferred one.

public class A {

    private Mode m;

    A() {
        m = Mode.CLEAR;
    }

    ...

    protected onClick(View v) {
        ...
        v.getBackground().SetColorFilter(R.color.azure, m);
        m = m.next();  // <-- I need something like this
        ...
    }

Answer 1

//Store these somewhere in your class
Mode[] modes = Mode.values();
int modeCount = modes.length;

protected void onClick(View v) {
    //Get the next mode, wrapping around if you reach the end
    int nextModeOrdinal = (m.ordinal() + 1) % modeCount;
    m = modes[nextModeOrdinal];
}

For Kotlin, you can declare an extension function on all enum types that would allow you to define a next() function on all enum instances:

/**
 * Returns the next enum value as declared in the class. If this is the last enum declared,
   this will wrap around to return the first declared enum.
 *
 * @param values an optional array of enum values to be used; this can be used in order to
 * cache access to the values() array of the enum type and reduce allocations if this is 
 * called frequently.
 */
inline fun <reified T : Enum<T>> Enum<T>.next(values: Array<T> = enumValues()) =
    values[(ordinal + 1) % values.size]

Then you can have something like:

enum class MyEnum {
    ONE, TWO, THREE
}

Then you can just use val two = MyEnum.ONE.next()

Answer 2

Implement this method:

public static Mode nextMode(Mode mode) {
    return (mode.ordinal() < Mode.values().length - 1) ? Mode.values()[mode.ordinal() + 1] : null;
}