Cách hiển thị PDF trong WebView Android

Giới thiệu

Hướng dẫn này trình bày cách hiển thị file PDF trong Android WebView. Vì WebView gốc không hỗ trợ render PDF trực tiếp, phương pháp phổ biến nhất là sử dụng Google Docs Viewer để nhúng PDF.

Các bước thực hiện

Bước 1: Tạo dự án mới

Tạo dự án Android Studio: File → New Project.

Bước 2: Layout activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <WebView
        android:id="@+id/web_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

Bước 3: MainActivity.java

package com.example.myapplication;

import android.os.Build;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.app.ProgressDialog;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Đang tải PDF...");
        progressDialog.setCancelable(false);

        WebView webView = findViewById(R.id.web_view);
        webView.requestFocus();
        
        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setBuiltInZoomControls(true);
        webSettings.setDisplayZoomControls(false);
        webSettings.setLoadWithOverviewMode(true);
        webSettings.setUseWideViewPort(true);

        // URL PDF cần hiển thị (phải accessible công khai)
        String pdfUrl = "https://gymnasium-wandlitz.de/vplan/vplan.pdf";
        
        // Sử dụng Google Docs Viewer để nhúng PDF
        // Format: https://docs.google.com/viewer?embedded=true&url={PDF_URL_ENCODED}
        String viewerUrl = "https://docs.google.com/viewer?embedded=true&url=" + 
                           android.net.Uri.encode(pdfUrl);

        webView.loadUrl(viewerUrl);

        webView.setWebViewClient(new WebViewClient() {
            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                view.loadUrl(url);
                return true;
            }

            @Override
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                progressDialog.dismiss();
                view.loadUrl("about:blank");
            }
        });

        webView.setWebChromeClient(new WebChromeClient() {
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                if (newProgress < 100) {
                    progressDialog.show();
                }
                if (newProgress == 100) {
                    progressDialog.dismiss();
                }
            }
        });
    }
}

Bước 4: AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
    package="com.example.myapplication">

    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">
            <intent-filter>
                

// Chỉ demo concept - cần xử lý ParcelFileDescriptor từ file local
ParcelFileDescriptor fd = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
PdfRenderer renderer = new PdfRenderer(fd);
int pageCount = renderer.getPageCount();

for (int i = 0; i < pageCount; i++) {
    PdfRenderer.Page page = renderer.openPage(i);
    Bitmap bitmap = Bitmap.createBitmap(page.getWidth(), page.getHeight(), Bitmap.Config.ARGB_8888);
    page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
    // Hiển thị bitmap lên ImageView
    page.close();
}
renderer.close();
fd.close();