Kotlin-for-Android-Developers | Companion App for the book

I'm learning the sample code about Anko at Kotlin for Android Developers (the book) https://github.com/antoniolg/Kotlin-for-Android-Developers

The Method 1 is from sample code and override parseList ,but it's hard to understand.

So I try to use the Method 2 instead of the Method 1, the Method 2 use original parseList function, but I get blank record when I use the Method 2, what error do I made in the Method 2

I get the error

java.lang.IllegalStateException: instance not initialized

you can test it at https://www.dropbox.com/s/gxeok1fyttsl54u/MyMirror.zip?dl=0

It seems that the code operator fun getValue(thisRef: Any?, property: KProperty<*>)... in UIApp causes the error.

But the code is from a sample code, I hardly don't change, you can see source code at https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/ui/App.kt

and

https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/extensions/DelegatesExtensions.kt

Why?

The following Code A is from https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/extensions/DelegatesExtensions.kt

I can use private var zipCode: Long by DelegatesExt.preference(this, ZIP_CODE, DEFAULT_ZIP) to invoke when I use Code A.

I don't understand why the author wrap class Preference(...) with object DelegatesExt

I think Code B is more simple, I can use private val zipCode: Long by Preference(this, ZIP_CODE, DEFAULT_ZIP) to invoke when I use Code B

Why need the class Preference be wrapped with object ?

Code A

I'm learning the sample code about 《Kotlin for android developers》 at https://github.com/antoniolg/Kotlin-for-Android-Developers

In the code .parseList { DayForecast(HashMap(it)) }, I can't understand what the function HashMap(it) will do. Is HashMap() a class and accept a parmater it?

And more, I think that the full code of class DayForecast(...).. is Code A, right?

Again, If I create a object var myDayForecast=DayForecast(10L,"Desciption",10,5,"http://www.a.com",10L), will myDayForecast.map be empty, right?

Code A

I'm learning the sample code about Anko at Kotlin for Android Developers (the book) at https://github.com/antoniolg/Kotlin-for-Android-Developers

I add a line var myMap=it before DayForecast(HashMap(it)), I think that the App will crash because the definition of parseList is parseList(parser: (Map) -> T), I can only assign a funtion to parseList.But the app can run correctly, why?

My modified ForecastDb.kt

The following sample code is from https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/data/db/ForecastDb.kt

I hope to display the value of "it" in the code .parseList{ DayForecast(HashMap(it)) }

So I set a breakpoint before the code val dailyForecast ..., and click Run -> Debug 'app menu in Android Studio, the press F7 to start Step Into, but I can't find how I can the value of "it" in the code .parseList{ DayForecast(HashMap(it)) }

How can I do? Thanks!

The following sample code is from Kotlin-for-Android-Developers at https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/data/db/ForecastDb.kt

I can't understand completely the code DayForecast(HashMap(it)). what does "it" mean?

And more, what happend when the parseList { DayForecast(HashMap(it)) } is executed ?

The Code A is from https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/data/db/ForecastDb.kt

I hope to use return instead of let, so I write the Code B, but the Code B can't be compiled, and I get two errors, why?

Error:(30, 10) 'return' is not allowed here

Error:(30, 45) Type mismatch: inferred type is CityForecast? but CityForecast was expected

The Code A

I'm a beginner of Kotlin. The following code is from Kotlin-for-Android-Developers at

https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master-june-2017/app/src/main/java/com/antonioleiva/weatherapp/ui/activities/MainActivity.kt

The fun startActivity have two parameter DetailActivity.ID to it.id and DetailActivity.CITY_NAME to result.city.

Could you explain the details about the two parameters?