How do I declare global variables on Android using Kotlin?

Question

How do I declare global variables on Android using Kotlin?

Kotlin Apps/ApplicationsMobile Development

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This example demonstrates how to declare global variables on Android using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
<TextView android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerHorizontal="true"
   android:layout_marginTop="70dp"
   android:background="#008080"
   android:padding="5dp"
   android:text="TutorialsPoint"
   android:textColor="#fff"
   android:textSize="24sp"
   android:textStyle="bold" />
<TextView android:id="@+id/text"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerInParent="true"
   android:textColor="@android:color/background_dark"
   android:textSize="24sp"
   android:textStyle="bold" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.os.Bundle
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   lateinit var textView: TextView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      textView = findViewById(R.id.text)
      textView.text = "Click"
      textView.setOnClickListener {
        val singleToneClass: SingleToneClass = SingleToneClass.instance
         singleToneClass.data = "this is sample"
         textView.text = singleToneClass.data
      }
   }
}
   class SingleToneClass private constructor() {
      var data: String? = null
      companion object {
       val instance = SingleToneClass()
    }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.q11">
   <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true" android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
       </activity>
    </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon  from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen.

Click here to download the project code.

Azhar

Published on 26-Sep-2020 18:49:55

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