Question

I’m trying to create a MouseEvent with certain modifiers for UnitTesting. I’m using J2SE and the following code fails to pass:

public void testMouseEventProblem() {
  MouseEvent event = new MouseEvent(new JPanel(), 1, System.currentTimeMillis(), 
    InputEvent.CTRL_DOWN_MASK | InputEvent.ALT_DOWN_MASK, 1,1, 0, false);

  assertEquals(InputEvent.CTRL_DOWN_MASK | InputEvent.ALT_DOWN_MASK, event.getModifiers());
}

It’s complaining saying “expected 640 but was 10”

What’s going on?

Answer 1

It gets internally converted to ALT_MASK and CTRL_MASK constants (8 + 2)

It happens in java.awt.event.InputEvent:405 in JDK 6

/**
 * Returns the modifier mask for this event.
 */
public int getModifiers() {
    return modifiers & (JDK_1_3_MODIFIERS | HIGH_MODIFIERS);
}

Try getModifiersEx():442:

public int getModifiersEx() {
    return modifiers & ~JDK_1_3_MODIFIERS;
}

As ALT_DOWN_MASK and friends are extended modifiers introduced after Java 1.3

Proof:

public class MouseEvt {
    public static void main(String[] args) {
        MouseEvent event = new MouseEvent(new JPanel(), 1, System
                .currentTimeMillis(), InputEvent.CTRL_DOWN_MASK
                | InputEvent.ALT_DOWN_MASK, 1, 1, 0, false);

        System.out.printf("%d - %d%n", InputEvent.CTRL_DOWN_MASK 
            | InputEvent.ALT_DOWN_MASK,
            event.getModifiersEx());
    }
}

Returns 640 - 640