Android create pdf document from webview with multiple pages

Creating Multi-Page PDF Documents from Android WebView

This article explores how to generate PDF documents from a webview in Android, with a focus on handling content that spans multiple pages.

Understanding the Challenge

Generating a PDF from a webview is a common task. However, capturing multi-page content requires additional considerations. The Android webview renders HTML and Javascript dynamically, often extending beyond the visible screen. Therefore, simply taking a snapshot of the current view would capture only a fragment of the content.

Core Techniques

Here are the core techniques we’ll explore to generate multi-page PDFs from a webview:

• HTML Structure and Page Breaks: We’ll use HTML’s built-in page-break features to define logical page divisions within our web content.
• WebView Rendering and Measurement: We’ll leverage the webview’s drawing capabilities to measure content and identify page boundaries.
• PDF Generation Library: We’ll integrate a library like iText to create the PDF document, drawing on the measured page content.

Implementation Steps

Let’s outline the steps involved in creating a multi-page PDF from a webview:

1. Project Setup

• Create a new Android Studio project.
• Add the iText dependency to your `build.gradle` file:

dependencies {
    implementation 'com.itextpdf:itextg:7.1.13'
}

2. Prepare HTML Content

The webview content should be structured to facilitate page breaks. For instance, use the HTML <div> element with the page-break-before or page-break-after CSS styles.

<div style="page-break-before: always;">
    <h2>Page 1 Content</h2>
</div>

<div style="page-break-after: always;">
    <h2>Page 2 Content</h2>
</div>

3. WebView Configuration

• Load your webview with the HTML content.
• Set the webview’s height to a reasonable value to enable scrolling.

webView.getSettings().setJavaScriptEnabled(true);
webView.loadData(htmlContent, "text/html", "UTF-8");
webView.setLayoutParams(new LinearLayout.LayoutParams(
    ViewGroup.LayoutParams.MATCH_PARENT, 
    1000 // Set a reasonable height
));

4. Measure Page Boundaries

After loading the content, we need to calculate the page boundaries within the webview. This involves iterating through the content and keeping track of the rendered height. Every time the height exceeds the page height, we mark it as a page break.

int pageHeight = webView.getHeight();
int currentHeight = 0;
List<Integer> pageBreaks = new ArrayList<Integer>();

// Iterate through the webview's content, calculating height and finding page breaks
// ...

if (currentHeight > pageHeight) {
    pageBreaks.add(currentHeight);
    currentHeight = 0; // Reset height for the new page
}

5. Create PDF with iText

Finally, we’ll use iText to generate the PDF. We’ll iterate through the page breaks and draw each page’s content onto the PDF.

Document document = new Document();
PdfWriter.getInstance(document, new FileOutputStream("multipage.pdf"));
document.open();

// ... iterate through the page breaks

// For each page, capture the view's content and draw onto the PDF
Bitmap bitmap = Bitmap.createBitmap(webView.getWidth(), pageHeight, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
webView.draw(canvas);

Image pdfImage = Image.getInstance(bitmap);
document.add(pdfImage);

document.close();

Conclusion

This approach provides a foundational framework for generating multi-page PDF documents from a webview in Android. You can adapt this technique to handle various scenarios by incorporating HTML, CSS, and iText features to customize your output.