Kotlin Android start new Activity

Question

I want to start another activity on Android but I get this error      Please specify constructor invocation  classifier  Page2  does not have a companion object   after instantiating the Intent class  What should I do to correct the error  My code   class MainActivity   AppCompatActivity          override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setContentView R layout activity main             fun buTestUpdateText2  view  View            val changePage   Intent this  Page2              Error   Please specify constructor invocation              classifier  Page2  does not have a companion object           startActivity changePage

User · Answer

Remember to add the activity you want to present  to your AndroidManifest xml too  -  That was the issue for me

User · Answer

Well  I found these 2 ways to be the simplest of all outcomes   Way  1   accoun btn setOnClickListener               startActivity Intent this MainActivity  SecondActivity  class java               Way 2   In a generic way       accoun btn setOnClickListener           startActivity lt SecondActivity gt  this             private inline fun  lt reified T gt  startActivity context  Context                startActivity Intent context  T  class java

User · Answer

This is because your Page2 class doesn t have a companion object which is similar to static in Java so to use your class  To pass your class as an argument to Intent  you will have to do something like this  val changePage   Intent this  Page2  class java

User · Answer

Try this  val intent   Intent this  Page2  class java  startActivity intent

User · Answer

You can use both Kotlin and Java files in your application    To switch between the two files  make sure you give them unique  lt  action android name    in AndroidManifest xml  like so                lt activity android name   MainActivityKotlin  gt                   lt intent-filter gt                       lt action android name  com genechuang basicfirebaseproject KotlinActivity   gt                       lt category android name  android intent category DEFAULT    gt                       lt action android name  android intent action MAIN    gt                       lt category android name  android intent category LAUNCHER    gt                   lt  intent-filter gt               lt  activity gt               lt activity                 android name  com genechuang basicfirebaseproject MainActivityJava                  android label  MainActivityJava   gt                   lt intent-filter gt                       lt action android name  com genechuang basicfirebaseproject JavaActivity    gt                       lt category android name  android intent category DEFAULT    gt                   lt  intent-filter gt               lt  activity gt    Then in your MainActivity kt  Kotlin file   to start an Activity written in Java  do this          val intent   Intent  com genechuang basicfirebaseproject JavaActivity           startActivity intent    In your MainActivityJava java  Java file   to start an Activity written in Kotlin  do this           Intent mIntent   new Intent  com genechuang basicfirebaseproject KotlinActivity            startActivity mIntent

User · Answer

Simply you can start an Activity in KOTLIN by using this simple method   val intent   Intent this  SecondActivity  class java  intent putExtra  key   value  startActivity intent

User · Answer

Details   Android Studio 3 1 4 Kotlin version  1 2 60   Step 1  Application       Get link to the context of you application    class MY APPLICATION NAME  Application          companion object           private lateinit var instance  MY APPLICATION NAME         fun getAppContext    Context   instance applicationContext            override fun onCreate             instance   this         super onCreate              Step 2  Add Router object  object Router       inline fun  lt reified T  Activity gt  start              val context    MY APPLICATION NAME getAppContext            val intent   Intent context  T  class java           context startActivity intent            Usage     You can start activity from any class  form Application  from any activity  from any fragment and other   Router start lt ANY ACTIVITY CLASS gt

User · Answer

From activity to activity  val intent   Intent this  YourActivity  class java  startActivity intent    From fragment to activity  val intent   Intent activity  YourActivity  class java  startActivity intent

User · Answer

another simple  way of navigating to another activity is Intent this  CodeActivity  class java  apply                       startActivity this

User · Answer

How about this to consider encapsulation  For example        override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setContentView R layout activity contents           val title   intent getStringExtra EXTRA TITLE     EXTRA TITLE DEFAULT          supportFragmentManager beginTransaction                add R id frame layout fragment  ContentsFragment newInstance                 commit                 Omit         companion object            private const val EXTRA TITLE    extra title          private const val EXTRA TITLE DEFAULT    No title           fun newIntent context  Context  title  String   Intent               val intent   Intent context  ContentsActivity  class java              intent putExtra EXTRA TITLE  title              return intent

User · Answer

val intentAct  Intent   Intent this YourCurrentActivity  TagentActivity  class java  startActivity intentAct

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You can generally simplify the specification of the parameter BlahActivity  class java by defining an inline reified generic function   inline fun  lt reified T  Activity gt  Context createIntent         Intent this  T  class java    Because that lets you do   startActivity createIntent lt Page2 gt        Or even simpler   inline fun  lt reified T  Activity gt  Activity startActivity         startActivity createIntent lt T gt           So it s now   startActivity lt Page2 gt

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This is my main activity where i take the username and password from edit text and setting to the intent  class MainActivity   AppCompatActivity     val userName   null val password   null override fun onCreate savedInstanceState  Bundle     super onCreate savedInstanceState  setContentView R layout activity main  button setOnClickListener       val intent   Intent this MainActivity SecondActivity  class java       var userName   username text toString       var password   password field text toString       intent putExtra  Username   userName      intent putExtra  Password   password      startActivity intent          This is my second activity where i have to receive values from the main activity  override fun onCreate savedInstanceState  Bundle     super onCreate savedInstanceState  setContentView R layout activity second  var strUser  String   intent getStringExtra  Username   var strPassword  String   intent getStringExtra  Password   user name setText  Seelan   passwor print setText  Seelan

User · Answer

I had a similar issue  I started to write my application in Kotlin  after I rewrote one of my activities I wanted to see if there are any issues  the problem was that I was not sure how to send an intent from java file to kotlin file   In this case I created a static function in kotlin  companion object   this function is getting a context  from the current activity  and returning the new intent while using the current context   java  context  while using the kotlin class     class java     Here is my code      this code will be in the kotlin activity - SearchActivity  companion object        fun newIntent context  Context   Intent           return Intent context  SearchActivity  class java                 this is how you call SearchActivity from MainActivity java Intent searchIntent   SearchActivity Companion newIntent this   startActivity searchIntent

User · Answer

You have to give the second argument of class type  You can also have it a little bit more tidy like below    startActivity Intent this  Page2  class java  apply       putExtra  extra 1   value1      putExtra  extra 2   value2      putExtra  extra 3   value3

User · Answer

To start a new Activity     startActivity Intent this CurrentClassName RequiredClassName  class java    So change your code to     class MainActivity   AppCompatActivity          override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setContentView R layout activity main             fun buTestUpdateText2  view  View            startActivity Intent this MainActivity ClassName  class java               Also like this           val intent   Intent this MainActivity ClassName  class java          startActivity intent

User · Answer

To start an Activity in java we wrote Intent this  Page2 class   basically you have to define Context in first parameter and destination class in second parameter  According to Intent method in source code -    public Intent Context packageContext  Class lt   gt  cls    As you can see we have to pass Class lt   gt  type in second parameter    By writing Intent this  Page2  we never specify we are going to pass class  we are trying to pass class type which is not acceptable   Use   class java which is alternative of  class in kotlin  Use below code to start your Activity  Intent this  Page2  class java    Example -  val intent   Intent this  NextActivity  class java     To pass any data to next activity intent putExtra  keyIdentifier   value     start your next activity startActivity intent

[android] Kotlin Android start new Activity

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