kotlin

问题 I am making a program that solves a math expression, for example, 2+2. Can I set an integer equal to something like this: val input = "2+2" input.toInt() 回答1: Kotlin doesn't have any built in ways for evaluating arbitrary expressions. The toInt function can only parse a String containing a single whole number (it's just a wrapper for Integer.parseInt). If you need this functionality, you'll have to parse and evaluate the expression yourself. This problem is no different than having to do it

问题 I have a code Volley Code val queue = Volley.newRequestQueue(context) val stringRequest = StringRequest(Request.Method.GET, linkTrang, Response.Listener<String> { response -> mTextView.text = "Response is: " + response.substring(0,500)); }, Response.ErrorListener { }) { } queue.add(stringRequest) How do I set a header called Authorization in this?? 回答1: I was able to do it in Kotlin using: val linkTrang = "YOUR URL" val queue = Volley.newRequestQueue(this) val stringRequest = object:

问题 I have a code Volley Code val queue = Volley.newRequestQueue(context) val stringRequest = StringRequest(Request.Method.GET, linkTrang, Response.Listener<String> { response -> mTextView.text = "Response is: " + response.substring(0,500)); }, Response.ErrorListener { }) { } queue.add(stringRequest) How do I set a header called Authorization in this?? 回答1: I was able to do it in Kotlin using: val linkTrang = "YOUR URL" val queue = Volley.newRequestQueue(this) val stringRequest = object:

问题 I am making an application that should do some things when I press the multimedia buttons. I know that I have to create a service and catch all the events there. I did everything the documentation recommended, but I still do not receive click events in the application. I followed the following guidelines for writing a similar application: https://developer.android.com/guide/topics/media-apps/mediabuttons https://developer.android.com/reference/androidx/media/session/MediaButtonReceiver.html

问题 I am making an application that should do some things when I press the multimedia buttons. I know that I have to create a service and catch all the events there. I did everything the documentation recommended, but I still do not receive click events in the application. I followed the following guidelines for writing a similar application: https://developer.android.com/guide/topics/media-apps/mediabuttons https://developer.android.com/reference/androidx/media/session/MediaButtonReceiver.html

问题 Problem I am building an application that requires some of the functionality of the Radar.io SDK, and so I decided to create plugin so after this project is over I can share the plugin with the rest of the Flutter Community. The problem is, I am not able to receive events in this plugin. This is important for the plugin since in order to receive events such as geolocation triggers and other background events this receiver needs to be receiving realtime information. I have successfully

问题 Let's have these classes: class A { fun foo(): A = this } class B: A() { fun bar() { ... } } Now I would like Kotlin to detect when I call foo on B , and give me the result typed as B . So that I can write: B().foo().bar() With kotlin 1.4.20, this is not possible - it would need an explicit cast to B after foo() . Perhaps it could be handled by the compiler, if it clearly sees that the function returns this . Or maybe we could hint it explicitly... class A { fun <Self> foo(): Self = this } I

问题 Let's have these classes: class A { fun foo(): A = this } class B: A() { fun bar() { ... } } Now I would like Kotlin to detect when I call foo on B , and give me the result typed as B . So that I can write: B().foo().bar() With kotlin 1.4.20, this is not possible - it would need an explicit cast to B after foo() . Perhaps it could be handled by the compiler, if it clearly sees that the function returns this . Or maybe we could hint it explicitly... class A { fun <Self> foo(): Self = this } I

问题 I am new in programming and want to make a file manager in android studio. I am facing problems in listing all device folders in API level 29 after getExteralStorageDirectory was deprecated. 回答1: According to the documentation, you will have to use ACTION_OPEN_DOCUMENT_TREE. This will provide you with the URI of selected directory , once you have the URI then you can access all the children of that directory . From docs Grant access to a directory's contents File management and media-creation

问题 I am new in programming and want to make a file manager in android studio. I am facing problems in listing all device folders in API level 29 after getExteralStorageDirectory was deprecated. 回答1: According to the documentation, you will have to use ACTION_OPEN_DOCUMENT_TREE. This will provide you with the URI of selected directory , once you have the URI then you can access all the children of that directory . From docs Grant access to a directory's contents File management and media-creation