selector – Page 5 – Tarik Billa

android button selector

December 15, 2022 by Tarik

You just need to set selector of button in your layout file. <Button android:id=”@+id/button1″ android:background=”@drawable/selector_xml_name” android:layout_width=”200dp” android:layout_height=”126dp” android:text=”Hello” /> and done. Edit Following is button_effect.xml file in drawable directory <?xml version=”1.0″ encoding=”utf-8″?> <selector xmlns:android=”http://schemas.android.com/apk/res/android”> <item android:drawable=”@drawable/numpad_button_bg_selected” android:state_selected=”true”></item> <item android:drawable=”@drawable/numpad_button_bg_pressed” android:state_pressed=”true”></item> <item android:drawable=”@drawable/numpad_button_bg_normal”></item> </selector> In this, you can see that there are 3 drawables, you just … Read more

Objective-C: Calling selectors with multiple arguments

November 21, 2022 by Tarik

In Objective-C, a selector’s signature consists of: The name of the method (in this case it would be ‘myTest’) (required) A ‘:’ (colon) following the method name if the method has an input. A name and ‘:’ for every additional input. Selectors have no knowledge of: The input types The method’s return type. Here’s a … Read more

How to get rid of the ‘undeclared selector’ warning

November 12, 2022 by Tarik

Another option would be to disable the warning with: #pragma GCC diagnostic ignored “-Wundeclared-selector” You can place this line in the .m file where the warning occurs. Update: It works also with LLVM like this: #pragma clang diagnostic push #pragma clang diagnostic ignored “-Wundeclared-selector” … your code here … #pragma clang diagnostic pop

“unrecognized selector sent to instance” error in Objective-C

October 26, 2022 by Tarik

It looks like you’re not memory managing the view controller properly and it is being deallocated at some point – which causes the numberButtonClicked: method to be sent to another object that is now occupying the memory that the view controller was previously occupying… Make sure you’re properly retaining/releasing your view controller.

What is the Swift equivalent of respondsToSelector?

October 13, 2022 by Tarik

As mentioned, in Swift most of the time you can achieve what you need with the ? optional unwrapper operator. This allows you to call a method on an object if and only if the object exists (not nil) and the method is implemented. In the case where you still need respondsToSelector:, it is still … Read more

@selector() in Swift?

September 9, 2022 by Tarik

Swift itself doesn’t use selectors — several design patterns that in Objective-C make use of selectors work differently in Swift. (For example, use optional chaining on protocol types or is/as tests instead of respondsToSelector:, and use closures wherever you can instead of performSelector: for better type/memory safety.) But there are still a number of important … Read more