PDF viewer events

Use the DocumentListener interface to handle document loading, page changes, and clicks. The Catalog app’s SimpleFragmentExample and CustomLayoutExample demonstrate this interface.

Registering a document listener

Register a listener with PdfFragment using addDocumentListener(). A fragment supports multiple document listeners:

fragment.addDocumentListener(myDocumentListener)

fragment.addDocumentListener(myDocumentListener);

Unregistering a document listener

To stop receiving events, pass the listener instance to removeDocumentListener(). Unregister listeners when you no longer need them, such as in your activity’s onStop()(opens in a new tab) method:

fragment.removeDocumentListener(myDocumentListener)

fragment.removeDocumentListener(myDocumentListener);

Document events

Nutrient calls the following DocumentListener methods in response to document events:

• Document loaded — Nutrient calls onDocumentLoaded(PdfDocument) when PdfFragment finishes loading the document. The callback receives the loaded PdfDocument.
• Loading failed — Nutrient calls onDocumentLoadFailed(Throwable) when loading fails. The Throwable(opens in a new tab) identifies the cause. Handle the error in your app — for example, by displaying a message.
• Page clicked — Nutrient calls onPageClick(PdfDocument, int, MotionEvent, PointF, Annotation) when a user clicks a page. The callback provides these parameters:
  • Document — The PdfDocument that the user clicked.
  • Page index — The int value identifying the clicked page.
  • Touch event — The MotionEvent(opens in a new tab) that triggered the click, including screen coordinates and pointer information.
  • PDF coordinates — The PointF(opens in a new tab) identifying the touch position in page coordinates. For details, refer to the coordinate space conversion guide.
  • Annotation — The Annotation that the user touched, or null if the user didn’t touch an annotation. Use this parameter for custom annotation handling.
• Background clicked — Nutrient calls onDocumentClick() when a user clicks the PdfFragment background outside any page.
• Page changed — Nutrient calls onPageChanged(PdfDocument, int) when the active page changes. The callback provides the active PdfDocument and the new page index.

Activity callbacks

PdfActivity implements DocumentListener by default. To handle events in a PdfActivity subclass, override the corresponding callback methods:

class MyActivity : PdfActivity() {

    override fun onDocumentLoaded(document : PdfDocument) {
        super.onDocumentLoaded(document)
        Toast.makeText(this, "Document has been loaded with ${document.pageCount} pages",
            Toast.LENGTH_SHORT).show()
    }

    override fun onDocumentLoadFailed(exception : Throwable) {
        super.onDocumentLoadFailed(exception)
        Toast.makeText(this, "Document loading failed!", Toast.LENGTH_SHORT).show()
        exception.printStackTrace()
    }
}

public class MyActivity extends PdfActivity {

    @Override
    public void onDocumentLoaded(@NonNull PdfDocument document) {
        super.onDocumentLoaded(document);
        Toast.makeText(this, String.format("Document has been loaded with %d pages",
            document.getPageCount()), Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onDocumentLoadFailed(Throwable exception) {
        super.onDocumentLoadFailed(exception);
        Toast.makeText(this, "Document loading failed!", Toast.LENGTH_SHORT).show();
        exception.printStackTrace();
    }
}