Enable download from WebView in Sketchware pro

To enable download from WebView, following steps are required.

1. Add a WebView webview1 in main.xml.

2. Switch ON AppCompat and design.

3. In permission manager add INTERNET permission.

4. In Java/Kotlin manager, add a new Java class file DownloadHelper.java. Put following codes in this file (change package name in first line to your own package name).


package com.my.newproject28;

import android.app.DownloadManager;
import android.content.Context;
import android.database.Cursor;
import android.media.MediaScannerConnection;
import android.net.Uri;
import android.os.Environment;
import android.os.Handler;
import android.util.Base64;
import android.util.Log;
import android.webkit.CookieManager;
import android.webkit.JavascriptInterface;
import android.webkit.WebView;
import android.widget.Toast;

import androidx.core.content.FileProvider;

import android.print.PrintManager;
import android.print.PrintDocumentAdapter;
import android.print.PrintAttributes;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLDecoder;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

public class DownloadHelper {

    private Context context;
    private WebView webView;
    private static final String JS_INTERFACE_NAME = "Android";
    private static final String TAG = "DownloadHelper";

    public DownloadHelper(Context context, WebView webView) {
        this.context = context;
        this.webView = webView;
        setupJavaScriptInterface();
    }

    // Set up JavaScript interface for WebView communication
    private void setupJavaScriptInterface() {
        webView.addJavascriptInterface(this, JS_INTERFACE_NAME);
    }

    // Extract filename from URL or Content-Disposition
    private String extractFilenameFromUrl(String url, String contentDisposition, String mimeType) {
        String filename = null;
        
        // Try to get filename from Content-Disposition header
        if (contentDisposition != null && !contentDisposition.isEmpty()) {
            filename = parseContentDisposition(contentDisposition);
        }
        
        // If not found in header, extract from URL
        if (filename == null || filename.isEmpty()) {
            filename = extractFilenameFromUrlPath(url);
        }
        
        // If still no filename, generate one based on mime type and timestamp
        if (filename == null || filename.isEmpty()) {
            filename = generateDefaultFilename(mimeType);
        }
        
        // Sanitize filename (remove invalid characters)
        filename = sanitizeFilename(filename);
        
        return filename;
    }

    // Parse Content-Disposition header to get filename
    private String parseContentDisposition(String contentDisposition) {
        try {
            // Look for filename* (RFC 5987) or filename parameter
            String[] parts = contentDisposition.split(";");
            for (String part : parts) {
                part = part.trim();
                if (part.toLowerCase().startsWith("filename*=")) {
                    // RFC 5987 format: filename*=UTF-8''filename.ext
                    String value = part.substring(part.indexOf("=") + 1);
                    if (value.startsWith("UTF-8''")) {
                        value = value.substring(7);
                        return URLDecoder.decode(value, "UTF-8");
                    }
                } else if (part.toLowerCase().startsWith("filename=")) {
                    // Simple filename format
                    String value = part.substring(part.indexOf("=") + 1);
                    // Remove quotes if present
                    if (value.startsWith("\"") && value.endsWith("\"")) {
                        value = value.substring(1, value.length() - 1);
                    }
                    return value;
                }
            }
        } catch (Exception e) {
            Log.e(TAG, "Error parsing Content-Disposition: " + e.getMessage());
        }
        return null;
    }

    // Extract filename from URL path
    private String extractFilenameFromUrlPath(String url) {
        try {
            // Remove query parameters
            String path = url;
            int queryIndex = url.indexOf('?');
            if (queryIndex > 0) {
                path = url.substring(0, queryIndex);
            }
            
            // Get last segment after '/'
            int lastSlash = path.lastIndexOf('/');
            if (lastSlash >= 0 && lastSlash < path.length() - 1) {
                String filename = path.substring(lastSlash + 1);
                if (!filename.isEmpty() && !filename.contains("/")) {
                    // URL decode the filename
                    return URLDecoder.decode(filename, "UTF-8");
                }
            }
        } catch (Exception e) {
            Log.e(TAG, "Error extracting filename from URL: " + e.getMessage());
        }
        return null;
    }

    // Generate default filename based on mime type and timestamp
    private String generateDefaultFilename(String mimeType) {
        String extension = getFileExtensionFromMimeType(mimeType);
        String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.US).format(new Date());
        return "download_" + timestamp + extension;
    }

    // Get file extension from mime type
    private String getFileExtensionFromMimeType(String mimeType) {
        if (mimeType == null) return ".bin";
        
        switch (mimeType.toLowerCase()) {
            case "application/pdf":
                return ".pdf";
            case "image/jpeg":
                return ".jpg";
            case "image/png":
                return ".png";
            case "image/gif":
                return ".gif";
            case "text/plain":
                return ".txt";
            case "text/html":
                return ".html";
            case "application/zip":
                return ".zip";
            case "application/x-zip-compressed":
                return ".zip";
            case "application/msword":
                return ".doc";
            case "application/vnd.openxmlformats-officedocument.wordprocessingml.document":
                return ".docx";
            case "application/vnd.ms-excel":
                return ".xls";
            case "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet":
                return ".xlsx";
            case "application/vnd.ms-powerpoint":
                return ".ppt";
            case "application/vnd.openxmlformats-officedocument.presentationml.presentation":
                return ".pptx";
            case "audio/mpeg":
                return ".mp3";
            case "audio/mp4":
                return ".m4a";
            case "video/mp4":
                return ".mp4";
            case "video/x-matroska":
                return ".mkv";
            default:
                return ".bin";
        }
    }

    // Remove invalid characters from filename
    private String sanitizeFilename(String filename) {
        if (filename == null) return "download.bin";
        
        // Remove path separators and other invalid characters
        filename = filename.replaceAll("[\\\\/:*?\"<>|]", "_");
        
        // Ensure filename is not empty after sanitization
        if (filename.isEmpty() || filename.equals(".") || filename.equals("..")) {
            return "download.bin";
        }
        
        // Truncate if too long
        if (filename.length() > 200) {
            String ext = "";
            int dotIndex = filename.lastIndexOf('.');
            if (dotIndex > 0 && dotIndex < filename.length() - 1) {
                ext = filename.substring(dotIndex);
                filename = filename.substring(0, Math.min(dotIndex, 190));
            }
            filename = filename + ext;
        }
        
        return filename;
    }

    // Get unique filename if file already exists
    private File getUniqueFile(File directory, String filename) {
        File file = new File(directory, filename);
        
        if (!file.exists()) {
            return file;
        }
        
        String baseName = filename;
        String extension = "";
        int dotIndex = filename.lastIndexOf('.');
        if (dotIndex > 0) {
            baseName = filename.substring(0, dotIndex);
            extension = filename.substring(dotIndex);
        }
        
        int counter = 1;
        while (file.exists()) {
            String newFilename = baseName + " (" + counter + ")" + extension;
            file = new File(directory, newFilename);
            counter++;
        }
        
        return file;
    }

    // Handle regular HTTP/HTTPS file downloads
    public void handleRegularDownload(String url, String userAgent, 
                                    String contentDisposition, String mimeType, 
                                    long contentLength) {
        try {
            // Extract correct filename
            String filename = extractFilenameFromUrl(url, contentDisposition, mimeType);
            
            Uri uri = Uri.parse(url);
            DownloadManager.Request request = new DownloadManager.Request(uri);
            
            request.setMimeType(mimeType);
            String cookies = CookieManager.getInstance().getCookie(url);
            if (cookies != null) {
                request.addRequestHeader("cookie", cookies);
            }
            request.addRequestHeader("User-Agent", userAgent);
            
            request.setTitle(filename);
            request.setDescription("Downloading file");
            request.allowScanningByMediaScanner();
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            
            // Set destination in Downloads folder
            File downloadsDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            File destinationFile = getUniqueFile(downloadsDir, filename);
            
            // Use Uri.fromFile for the destination
            request.setDestinationUri(Uri.fromFile(destinationFile));
            
            DownloadManager dm = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
            if (dm != null) {
                long downloadId = dm.enqueue(request);
                Log.d(TAG, "Download started with ID: " + downloadId + ", filename: " + destinationFile.getName());
                
                // Monitor download completion to scan the file
                monitorDownloadCompletion(dm, downloadId, destinationFile);
                
                Toast.makeText(context, "Download started: " + destinationFile.getName(), Toast.LENGTH_LONG).show();
            }
        } catch (Exception e) {
            Log.e(TAG, "Regular download failed: " + e.getMessage());
            Toast.makeText(context, "Download failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
        }
    }

    // Monitor download completion to scan the file
    private void monitorDownloadCompletion(final DownloadManager dm, final long downloadId, final File file) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                boolean downloading = true;
                while (downloading) {
                    DownloadManager.Query q = new DownloadManager.Query();
                    q.setFilterById(downloadId);
                    Cursor cursor = dm.query(q);
                    if (cursor != null && cursor.moveToFirst()) {
                        int status = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
                        if (status == DownloadManager.STATUS_SUCCESSFUL) {
                            downloading = false;
                            // Scan the file so it appears in gallery/file managers
                            MediaScannerConnection.scanFile(context, 
                                new String[]{file.getAbsolutePath()}, null, null);
                            Log.d(TAG, "Download completed and scanned: " + file.getName());
                        } else if (status == DownloadManager.STATUS_FAILED) {
                            downloading = false;
                            Log.e(TAG, "Download failed");
                        }
                        cursor.close();
                    }
                    try {
                        Thread.sleep(1000); // Check every second
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }

    // Handle blob URL downloads using JavaScript fetch API
    public void handleBlobUrlDownload(String blobUrl, String fileName, String mimeType) {
        try {
            // If filename is not provided or is empty, generate one
            if (fileName == null || fileName.isEmpty()) {
                fileName = generateDefaultFilename(mimeType);
            } else {
                fileName = sanitizeFilename(fileName);
            }
            
            final String javascript = "javascript: (function() {" +
                "var blobUrl = '" + blobUrl + "';" +
                "fetch(blobUrl)" +
                ".then(response => response.blob())" +
                ".then(blob => {" +
                "   var reader = new FileReader();" +
                "   reader.onloadend = function() {" +
                "       var base64data = reader.result;" +
                "       " + JS_INTERFACE_NAME + ".handleBase64Data(base64data, '" + mimeType + "', '" + fileName + "');" +
                "   };" +
                "   reader.readAsDataURL(blob);" +
                "})" +
                ".catch(error => {" +
                "   console.error('Blob download error:', error);" +
                "   " + JS_INTERFACE_NAME + ".handleBase64Data('', '" + mimeType + "', '" + fileName + "');" +
                "});" +
                "})()";
            
            webView.post(new Runnable() {
                @Override
                public void run() {
                    webView.loadUrl(javascript);
                    Log.d(TAG, "Blob download initiated");
                }
            });
        } catch (Exception e) {
            Log.e(TAG, "Blob URL download setup failed: " + e.getMessage());
            Toast.makeText(context, "Download setup failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
        }
    }

    // JavaScript interface method to handle base64 data from blob URLs
    @JavascriptInterface
    public void handleBase64Data(String base64Data, String mimeType, String fileName) {
        try {
            if (base64Data == null || base64Data.isEmpty()) {
                throw new Exception("Empty base64 data received");
            }
            
            String pureBase64 = base64Data.substring(base64Data.indexOf(",") + 1);
            byte[] fileData = Base64.decode(pureBase64, Base64.DEFAULT);
            
            saveBase64Data(fileData, fileName, mimeType);
            
        } catch (final Exception e) {
            Log.e(TAG, "Blob download failed: " + e.getMessage());
            new Handler(context.getMainLooper()).post(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(context, "Download failed: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }
            });
        }
    }

    // Save base64 data to Downloads directory with duplicate handling
    public void saveBase64Data(byte[] data, final String fileName, String mimeType) {
        try {
            File downloadsDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            if (!downloadsDir.exists()) {
                downloadsDir.mkdirs();
            }
            
            // Sanitize filename and handle duplicates
            String safeFileName = sanitizeFilename(fileName);
            File file = getUniqueFile(downloadsDir, safeFileName);
            
            final String savedFileName = file.getName();
            
            // Write file
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(data);
            fos.close();
            
            // Scan file so it appears in gallery/file managers
            MediaScannerConnection.scanFile(context, new String[]{file.getAbsolutePath()}, 
                new String[]{mimeType}, new MediaScannerConnection.OnScanCompletedListener() {
                    @Override
                    public void onScanCompleted(String path, Uri uri) {
                        Log.d(TAG, "Media scan completed for: " + path);
                    }
                });
            
            // Show success message
            new Handler(context.getMainLooper()).post(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(context, "File saved: " + savedFileName, Toast.LENGTH_LONG).show();
                }
            });
            
            Log.d(TAG, "File saved successfully: " + file.getAbsolutePath());
            
        } catch (final Exception e) {
            Log.e(TAG, "Save base64 data failed: " + e.getMessage());
            new Handler(context.getMainLooper()).post(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(context, "Save failed: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }
            });
        }
    }

    // Clean up JavaScript interface when no longer needed
    public void cleanup() {
        try {
            webView.removeJavascriptInterface(JS_INTERFACE_NAME);
            Log.d(TAG, "Cleanup completed");
        } catch (Exception e) {
            Log.e(TAG, "Cleanup failed: " + e.getMessage());
        }
    }
}

5. In onCreate, put following codes (change the url to the url you want to load).


WebSettings settings = binding.webview1.getSettings();
settings.setJavaScriptEnabled(true);
settings.setDomStorageEnabled(true);
settings.setAllowFileAccess(true);
settings.setAllowContentAccess(true);
settings.setAllowFileAccessFromFileURLs(true);
settings.setAllowUniversalAccessFromFileURLs(true);

// Initialize download helper
final DownloadHelper downloadHelper = new DownloadHelper(this, binding.webview1);

binding.webview1.loadUrl("https://www.apkmirror.com/");

// Handle download requests
binding.webview1.setDownloadListener(new DownloadListener() {
    @Override
    public void onDownloadStart(String url, String userAgent, 
    String contentDisposition, String mimeType, 
    long contentLength) {
        
        if (url.startsWith("blob:") || url.startsWith("data:")) {
            // For blob URLs, let the DownloadHelper generate a filename
            downloadHelper.handleBlobUrlDownload(
                url,           // Blob URL
                null,          // Let DownloadHelper generate filename
                mimeType
            );
        } else {
            // For regular HTTP downloads
            downloadHelper.handleRegularDownload(
                url,
                userAgent,
                contentDisposition,
                mimeType,
                contentLength
            );
        }
    }
});

6. Run the project.

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