android/app/src/main/java/io/v/android/apps/reader/PdfViewWrapper.java

// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package io.v.android.apps.reader;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.webkit.JavascriptInterface;
import android.webkit.WebChromeClient;
import android.webkit.WebResourceRequest;
import android.webkit.WebResourceResponse;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Wrapper class for the PDF Viewer library.
 *
 * May be replaced with another library if needed.
 */
public class PdfViewWrapper extends WebView {

    private static final String TAG = PdfViewWrapper.class.getSimpleName();

    private int mPageCount;

    public PdfViewWrapper(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public void init() {
        WebSettings settings = getSettings();
        settings.setJavaScriptEnabled(true);
        settings.setAllowUniversalAccessFromFileURLs(true);

        setWebChromeClient(new WebChromeClient());

        setWebViewClient(new WebViewClient() {
            @Override
            public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
                Log.i(TAG, "shouldInterceptRequest called");

                File file = new File(request.getUrl().getPath());
                Log.i(TAG, "file path: " + file.getPath());

                try {
                    // Should NOT close the stream here, so that the stream can be read by WebView.
                    InputStream inputStream = new FileInputStream(file);

                    Log.i(TAG, "returning a custom WebResourceResponse");
                    return new WebResourceResponse("application/pdf", "binary", inputStream);
                } catch (IOException e) {
                    Log.i(TAG, "falling back to super.shouldInterceptRequest");
                    return super.shouldInterceptRequest(view, request);
                }
            }
        });

        addJavascriptInterface(new JSInterface(), "android");

        loadUrl("file:///android_asset/pdfjs/pdf-web-view.html");
    }

    /**
     * Loads the PDF file at the given path into the pdf.js component within WebView.
     * NOTE: must be called after the page loading is finished.
     */
    public void loadPdfFile(String filePath) {
        evaluateJavascript("window.client.open(\"" + filePath + "\");", null);

        // leave the page count as 0 until the page count value is properly set from JS side.
        mPageCount = 0;
    }

    /**
     * Jumps to the given page number. Page number is one-based.
     *
     * @param page the page number to jump to. Page number is one-based.
     */
    public void setPage(int page) {
        evaluateJavascript("window.client.page(" + page + ");", null);
    }

    public int getPageCount() {
        return mPageCount;
    }

    /**
     * This class provides public methods that can be called from the JavaScript side.
     */
    private class JSInterface {

        private final String TAG = JSInterface.class.getSimpleName();

        @JavascriptInterface
        public void setPageCount(int pageCount) {
            Log.d(TAG, "setPageCount(" + pageCount + ") called.");
            mPageCount = pageCount;
        }
    }

}