Generate PDF File in Android using Jetpack Compose

package com.geeksforgeeks.demo

import android.Manifest
import android.content.Context
import android.graphics.*
import android.graphics.pdf.PdfDocument
import android.os.Bundle
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.result.contract.ActivityResultContracts
import androidx.compose.foundation.layout.*
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.toArgb
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.*
import com.geeksforgeeks.demo.ui.theme.DemoTheme
import java.io.File
import java.io.FileOutputStream

class MainActivity : ComponentActivity() {

    // Launcher for handling permission requests
    private val requestPermissionsLauncher =
        registerForActivityResult(ActivityResultContracts.RequestMultiplePermissions()) { permissions ->
            val granted = permissions.entries.all { it.value }
            if (granted) {
                Toast.makeText(this, "Permissions Granted.", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this, "Permission Denied.", Toast.LENGTH_SHORT).show()
            }
        }

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

        // Check and request required permissions
        checkAndRequestPermissions()

        // Set the Jetpack Compose UI
        setContent {
            DemoTheme(dynamicColor = false, darkTheme = false) {
                Surface(color = Color.White) {
                
                    // Display the UI component
                    PdfGenerator() 
                }
            }
        }
    }

    // Function to check and request
    // necessary permissions
    private fun checkAndRequestPermissions() {
        val requiredPermissions = mutableListOf<String>()

        // Request WRITE_EXTERNAL_STORAGE only
        // for Android 9 and below
        if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.Q) {
            requiredPermissions.add(Manifest.permission.WRITE_EXTERNAL_STORAGE)
        }

        // Request permissions if any are needed
        if (requiredPermissions.isNotEmpty()) {
            requestPermissionsLauncher.launch(requiredPermissions.toTypedArray())
        }
    }
}

@Composable
fun PdfGenerator() {
    val context = LocalContext.current

    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        // Title text
        Text(
            text = "PDF Generator",
            color = Color.Black,
            fontWeight = FontWeight.Bold,
            textAlign = TextAlign.Center,
            fontSize = 20.sp
        )

        Spacer(modifier = Modifier.height(40.dp))

        // Button to generate the PDF
        Button(
            modifier = Modifier
                .fillMaxWidth()
                .padding(20.dp),
            onClick = { generatePDF(context) }
        ) {
            Text(modifier = Modifier.padding(6.dp), text = "Generate PDF")
        }
    }
}

// Function to generate a simple PDF document
fun generatePDF(context: Context) {

    // Define the page height
    val pageHeight = 1120  
    
    // Define the page width
    val pageWidth = 792    
    
    // Create a new PDF document
    val pdfDocument = PdfDocument() 

    // Paint object for drawing
    val paint = Paint() 
    
    // Paint object for text
    val title = Paint() 

    // Load an image from resources 
    // (ensure R.drawable.gfg_logo exists)
    val bmp: Bitmap = BitmapFactory.decodeResource(context.resources, R.drawable.gfg_logo)
    
    // Resize the image
    val scaledBitmap = Bitmap.createScaledBitmap(bmp, 140, 140, false) 

    // Create a PDF page with specified width and height
    val myPageInfo = PdfDocument.PageInfo.Builder(pageWidth, pageHeight, 1).create()
    val myPage = pdfDocument.startPage(myPageInfo)

    // Get the canvas to draw on
    val canvas: Canvas = myPage.canvas

    // Draw the image onto the PDF
    canvas.drawBitmap(scaledBitmap, 56F, 40F, paint)

    // Configure text properties
    title.apply {
        typeface = Typeface.create(Typeface.DEFAULT, Typeface.NORMAL)
        textSize = 16F
        color = Color.Black.toArgb()
    }

    // Draw text onto the PDF
    canvas.drawText("A portal for IT professionals.", 209F, 120F, title)
    canvas.drawText("Geeks for Geeks", 209F, 100F, title)
    title.textAlign = Paint.Align.CENTER
    canvas.drawText("This is a sample document which we have created.", 396F, 560F, title)

    // Finish writing to the page
    pdfDocument.finishPage(myPage)

    // Define a file path in the app's
    // private storage (no permissions required)
    val file = File(context.getExternalFilesDir(null), "GFG.pdf")

    try {
    
        // Write the PDF to the file
        pdfDocument.writeTo(FileOutputStream(file))
        Toast.makeText(context, "PDF saved at ${file.absolutePath}", Toast.LENGTH_SHORT).show()
    } catch (e: Exception) {
        e.printStackTrace()
        Toast.makeText(context, "Failed to generate PDF", Toast.LENGTH_SHORT).show()
    }

    // Close the document
    pdfDocument.close()
}