Navigation Bar Back Button Custom Icon?

Is it possible to change the navigation bar (image bellow for reference) back button icon programmatically? Let's say in a certain moment I'd like to change it to be the arrow down

Solution 1:

What I ended up doing was creating a popup window over the soft input and making the soft input "arrow down" button do what I wanted on that pop up window. To control what the soft input "arrow down" button does I had to create a class that extends EditText and override:

public boolean onKeyPreIme(int keyCode, KeyEvent event)