如何在 Android 上使用 Kotlin 显示 Toast？

Question

In different Kotlin examples for Android I see toast("Some message...") or toastLong("Some long message") . For example:

view.setOnClickListener { toast("Click") }

As I understand, it is an Extension Function for Activity .

How and where do you define this toast() function so that you are able to use it throughout the project?

Answer 1

It can be an extension function for Context :

fun Context.toast(message: CharSequence) = 
    Toast.makeText(this, message, Toast.LENGTH_SHORT).show()

You can place this anywhere in your project, where exactly is up to you. For example, you can define a file mypackage.util.ContextExtensions.kt and put it there as a top level function.

Whenever you have access to a Context instance, you can import this function and use it:

import mypackage.util.ContextExtensions.toast

fun myFun(context: Context) {
    context.toast("Hello world!")
}

Answer 2

这是 Kotlin 中的一行解决方案：

Toast.makeText(this@MainActivity, "Its toast!", Toast.LENGTH_SHORT).show()

Answer 3

It's actually a part of Anko , an extension for Kotlin. Syntax is as follows:

toast("Hi there!")
toast(R.string.message)
longToast("Wow, such a duration")

In your app-level build.gradle , add implementation "org.jetbrains.anko:anko-common:0.8.3"

Add import org.jetbrains.anko.toast to your Activity.

Answer 4

Try this

In Activity

Toast.makeText(applicationContext, "Test", Toast.LENGTH_LONG).show()

or

Toast.makeText(this@MainActiivty, "Test", Toast.LENGTH_LONG).show()

In Fragment

Toast.makeText(activity, "Test", Toast.LENGTH_LONG).show()

or

Toast.makeText(activity?.applicationContext, "Test", Toast.LENGTH_LONG).show()

Answer 5

If you don't want to use anko and want to create your own Toast extension. You can create inline(or without inline) extensions defined in a kotlin file(with no class) and with that you can access this function in any class.

inline fun Context.toast(message:String){
   Toast.makeText(this, message , duration).show()
}

Usage:

In Activity,

toast("Toast Message")

In Fragment,

context?.toast("Toast Message")

Answer 6

While using Anko with Kotlin , inside fragment use either:

 activity.toast("string message") 

or

 context.toast("string message")

or

 view.holder.context.toast("string message")

Answer 7

A very simple extension.

Add this to a toast.kt file

import android.content.Context
import android.widget.Toast
import androidx.fragment.app.Fragment

inline fun Context.toast(message:()->String){
   Toast.makeText(this, message() , Toast.LENGTH_LONG).show()
}

inline fun Fragment.toast(message:()->String){
   Toast.makeText(this.context, message() , Toast.LENGTH_LONG).show()
}

then you'll have

toast {
   "Hello World"
}

in both fragment & activity.

Answer 8

I have found very easy way to Toast from given link https://gist.github.com/felipearimateia/ee651e2694c21de2c812063980b89ca3 . In this link Activity is used instead of Context. Try it.

Answer 9

With this extension function for Toasts , you can call them in Activities as well as Fragments, you can pass this as Context for Activities or getApplication() for Fragments, also it's generated with Toast.LENGTH_SHORT as default, so you don't need to worry to pass it as a parameter, but you can overwrite it as well if you need.

Kotlin

fun Context.showToast(message: String, duration: Int = Toast.LENGTH_SHORT){
        Toast.makeText(context, message , duration).show()
    }

Usage

showToast("John Doe")

if you want to override the duration.

showToast("John Doe", Toast.LENGTH_LONG)

Answer 10

Show a Toast not from the UI Thread , in a Fragment

activity?.runOnUiThread {
        Toast.makeText(context, "Image saved to the Gallery", Toast.LENGTH_SHORT).show()
    }

Answer 11

Android Toast for Kotlin

Activity

Toast.makeText(applicationContext, "message...", Toast.LENGTH_SHORT).show()

Fragment

Toast.makeText(activity, "message...", Toast.LENGTH_SHORT).show()

Answer 12

It's simply an extension function for Context (like other pointed out already).

You can find a lot of pre-defined android extension functions in Anko , which is probably what many of the tutorials use as well.

Answer 13

Just to add on @nhaarman's answer --> you probably want to add the resourceId support as well

fun Context.toast(resourceId: Int) = toast(getString(resourceId))
fun Context.toast(message: CharSequence) = 
    Toast.makeText(this, message, Toast.LENGTH_SHORT).show()

Answer 14

Download source code from here ( Custom Toast In Android Kotlin )

fun Toast.createToast(context: Context, message: String, gravity: Int, duration: Int, backgroucolor: String, imagebackgroud: Int) {
        val inflater: LayoutInflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        /*first parameter is the layout you made
        second parameter is the root view in that xml
         */
        val layout = inflater.inflate(R.layout.custom_toast, (context as Activity).findViewById(R.id.custom_toast_container))

        layout.findViewById(R.id.tv_message).text = message
        layout.setBackgroundColor(Color.parseColor(backgroucolor))
        layout.findViewById(R.id.iv_image).iv_image.setImageResource(imagebackgroud)
        setGravity(gravity, 0, 100)
        setDuration(Toast.LENGTH_LONG);

        setView(layout);
        show()
    }

Thanks!

Answer 15

the way I use it simply creating an Object / Class

object UtilKotlin {
    fun showMessage(context: Context, message: String) {
        Toast.makeText(context, message, Toast.LENGTH_SHORT).show()
    }
}

and calling the method

UtilKotlin.showMessage(activity, "Sets 0 !") // in activity trying this

Answer 16

Custom Toast with Background color Text size AND NO XML file inflated Try the code without setting the Background color

    fun theTOAST(){

    val toast = Toast.makeText(this@MainActivity, "Use View Person List",Toast.LENGTH_LONG)
    val view = toast.view
    view.setBackgroundColor(Color.TRANSPARENT)
    val text = view.findViewById(android.R.id.message) as TextView
    text.setTextColor(Color.BLUE)
    text.textSize = (18F)
    toast.show()
}

Answer 17

Here is extension of toast for activity or fragment

fun showToast(context: Context,@StringRes string : Int, duration: Int = Toast.LENGTH_SHORT){
  Toast.makeText(context,string,duration).show()
 }


inline fun Context.toast(message:()->String){
 Toast.makeText(this, message() , Toast.LENGTH_LONG).show()
}


inline fun Fragment.toast(message: () -> String, duration: () -> Int = { Toast.LENGTH_LONG }){
 Toast.makeText(this.context,message(),duration()).show()
}


inline fun AppCompatActivity.toast(message: () -> String, duration: () -> Int = { Toast.LENGTH_LONG }){
 Toast.makeText(this.applicationContext,message(),duration()).show()
}

If you want simple toast just call first method both fragment and activity

 showToast(yourContext,"your message")  or showToast(yourContext,"your message",1200L)

Or

toast {
 "Your message"
}

Or

toast({"your message"}) or toast({"your messge"},{your duration = 1200L})