l RESULT l EXPLANATION 1. designate the id on xml file android:id="@+id/tvInput" 2. enroll the id on kotlin file 1) import import android.widget.Button import android.widget.TextView 2) define the value private var tvInput : TextView? = null 2) initialize the value using find view by 더보기 id + r. id. + (name of id) tvInput = findViewById(R.id.tvInput) 3. use the value on the method 1) set the val..

1. define the color name with colors.xml 1) res>> values >> colors.xml 2) designate the color #636262 2. change the primary color 1) res>> values> themes> themse.xml 2) i changed purple color into light gray at the primary tag @color/light_gray 3. confirm the result

1. throw throw (keyword) + name of the customized exception + (code to throw) 2. normal code fun main() { val str = numberFunction("73") println(str) } fun numberFunction(str:String):Int{ return Integer.parseInt(str) } The variable 'str' has string type, and it is parsed by the function 'numberFunction' to int. Thus, the program prints '73' 3. error code fun main() { val str = numberFunction("7...

This posting is about the explanation of the exceptions in Kotlin. 1. EXCEPTION Exception is related to the problem that terminates the program or run the program on the wrong purpose. By knowing and handling the exceptions, we can make the appropriate program. 1) Unchecked Exception : extends the Runtime Exception Class User-made mistakes or wrong logic from the developer usually makes this exc..

1. Kotlin cast operator You can use 'as' to apply type casting. However, if the type can not be assigned to the specific target data, it receives the ClassCastException. If you want to remove the exception, you should use 'as?' instead of the 'as' operator. This operator returns 'null' if the class cast exception occurs. 2. Unsafe operator 'as' The operator 'as' can not assign data to unrelated ..

Difference l Explanation While nested class can not approach to the outer class's properties, inner class is able to approach them. l Code l explanation 'unresolved reference' has been occurred since the value named 'topic' is defined in outer class 'Seoul'. This value can not be used inside of the nested class 'Hongdae'. 1. nested class we call the class (which is in the other class ) nested cl..