Recently, I made a decision to disallow programmers to use android:onClick XML attributes to add click event listeners. Existing usages will be removed too. Actually, the attribute itself was a very bad design, considering that web frontend developers has switched from onclick HTML attribute to addEventListener API for a long time.

Here are the real reasons why android:onClick XML attribute should be avoided:

• If an ancestor element has theme applied, android:onClick no longer works, because the program will look for the click handler from ContextThemeWrapper instead of Activity (see http://stackoverflow.com/questions/29525644/). When applying a theme, programmers may not realize the problem.
• Android look for the specified method from the parent Activity. When programmers change an Activity into a Fragment, they may be ignoring this problem.
• To make the two problems above more severe, onClick uses reflection. It therefore prevents the compiler from telling you problems. You app will crash at run time.
• As it uses reflection, performance will be compromised.
• Android provides android:onClick attribute, but no android:onChange or any other XML attributes for event listeners. Considering click listeners aren't really different from other event listeners, keeping them consistent will be good.
• When using android:onClick, one must create a public method with parameter (View view). Android Lint will then complain "unused parameter".
• Adding a public method is not elegant in any way.