/*
  (c) naturalprogramming.com

   2022-09-21 File created by Kari Laitinen
   2022-09-28 Last modification.

    This simple app contains a Text and a Button, and Spacers to
    center the other components vertically.

    This is an Android app made of this single file.

    If you want to test this app, create an Android Compose project
    with the package name shown below. Then, store this file
    to the folder where MainActivity.kt is and make the following
    change to AndroidManifest.xml:
    android:name=".ButtonDemoCActivity"

    Some 'warnings':
    - tab size in this file is 3 spaces
    - underscores are used in the names invented by the programmer

*/

package button.democ

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import button.democ.ui.theme.ButtonDemoCTheme

class ButtonDemoCActivity : ComponentActivity()
{
   override fun onCreate( savedInstanceState: Bundle? )
   {
      super.onCreate( savedInstanceState )

      setContent {

         ButtonDemoCTheme {
            // A surface container using the 'background' color from the theme
            Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background)
            {
               val changing_text = remember { mutableStateOf("Hello!") }

               Column( horizontalAlignment = Alignment.CenterHorizontally )
               {

                  Spacer( modifier = Modifier.weight( 0.5F ) )

                  // Text had to be put inside a Box in order to center it
                  // inside the upper half of the screen.

                  Box( modifier = Modifier.weight( 1F ),
                       contentAlignment = Alignment.Center )
                  {
                     Text(
                        changing_text.value, fontSize = 40.sp,
                        //modifier = Modifier.weight(1F)
                     )
                  }

                  Button( onClick =
                  {
                     if ( changing_text.value == "Hello!" )
                     {
                        changing_text.value = "Well done!"
                     }
                     else
                     {
                        changing_text.value = "Hello!"
                     }
                  },
                     modifier = Modifier.requiredHeight( 100.dp ).
                                        requiredWidth( 200.dp).weight( 1F ),
                     shape = RoundedCornerShape( 20.dp ),
                     colors = ButtonDefaults.buttonColors( backgroundColor = Color.Cyan ) )
                  {
                     Text( text = "PRESS", fontSize = 32.sp )
                  }

                  Spacer( modifier = Modifier.weight( 0.5F ) )
               }

            }
         }
      }
   }
}