Q:

Is it possible to set the `error` string with CheckBox?

For EditText, if I set error, the string is displayed when the user taps the EditText. But if I set error on a CheckBox, can it be read? I have tried tapping the red exclamation circle, but the message was not shown.
myCheckBox.error = "Can the user read this error message?"

A:

Yes, sure you can do it, just specify this two properties in xml for CheckBox:
 android:focusableInTouchMode="true"
 android:focusable="true"

Edit: As you stated, if you move focus to other view, you need twice to tap to check/uncheck CheckBox. One tab to set focus, second to actually check/uncheck. One simple (but no elegant) solution is to set OnFocusChangeListener like this:
        chBox.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if(hasFocus){
                    chBox.setChecked(!chBox.isChecked());
                }
            }
        });

