Simple if-statement seems to be not executing some portion of code

When I press a button, the code below is called. If currentImageButton is null, and it's Drawable is null (which it will be the first time it is called), then simply print a message to the console. Otherwise, set the background of my canvas to an image in my Drawable folder. I know the condition is sometimes true, because "currentImageButton DOES have a drawing cache" is printed out after the first button press.

            ImageButton imageButton = (ImageButton) view;

            if (currentImageButton != null && currentImageButton.getDrawable() != null) {

                Drawable myDrawable = getResources().getDrawable(R.drawable.start_checklist_pressed);
                Bitmap anImage      = ((BitmapDrawable) myDrawable).getBitmap();
                canvas.drawBitmap(anImage);

                System.out.println("currentImageButton DOES have a drawing cache");
            } else {
                System.out.println("currentImageButton has no drawing cache");

            }

            currentImageButton = imageButton;

However, when the condition is true, the background of my canvas is never set. The weird thing is, I know those lines of code work, because when I bring the last line underneath the first, everything works perfectly, although that line seems completely irrelevant to whether or not the background gets set. This code works:

            ImageButton imageButton = (ImageButton) view;
            currentImageButton = imageButton;

            if (currentImageButton != null && currentImageButton.getDrawable() != null) {

                Drawable myDrawable = getResources().getDrawable(R.drawable.start_checklist_pressed);
                Bitmap anImage      = ((BitmapDrawable) myDrawable).getBitmap();
                canvas.drawBitmap(anImage);

                System.out.println("currentImageButton DOES have a drawing cache");
            } else {
                System.out.println("currentImageButton has no drawing cache");

            }

What is going on here?

EDIT

Also, another weird thing. If I change the condition to OR:

if (currentImageButton != null || currentImageButton.getDrawable() != null)

I get a null pointer exception on this line. How is it possible for a null pointer exception to be thrown on a check for null?

java.lang.NullPointerException
        at com.brettrosen.atls.fragments.PrearrivalPlan$6.onClick(PrearrivalPlan.java:416)
        at android.view.View.performClick(View.java:4192)
        at android.view.View$PerformClick.run(View.java:17327)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5019)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
        at dalvik.system.NativeStart.main(Native Method)

EDIT2

currentImageButton is declared as follows, as a global variable:

public ImageButton currentImageButton;