// ==================== 文件：build.gradle ====================
// 在 app 模塊的 build.gradle 中添加依賴
dependencies {
    implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'
    implementation 'com.squareup.okhttp3:okhttp:4.9.3'
}
 
 
// ==================== 文件：PdfViewerActivity.java ====================
package com.example.pdfreader;
 
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;
 
import androidx.appcompat.app.AppCompatActivity;
 
import com.github.barteksc.pdfviewer.PDFView;
import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
 
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
 
/**
 * 在線 PDF 閱讀器示例
 */
public class PdfViewerActivity extends AppCompatActivity {
 
    private static final String PDF_URL = "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";
 
    private PDFView pdfView;
    private ProgressBar progressBar;
 
    private OkHttpClient client = new OkHttpClient();
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_viewer);
 
        pdfView = findViewById(R.id.pdfView);
        progressBar = findViewById(R.id.progressBar);
 
        // 下載并顯示 PDF
        downloadPdfFromUrl(PDF_URL);
    }
 
    /**
     * 從網(wǎng)絡下載 PDF 文件
     */
    private void downloadPdfFromUrl(String url) {
        progressBar.setVisibility(View.VISIBLE);
 
        Request request = new Request.Builder().url(url).build();
        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                runOnUiThread(() -> {
                    progressBar.setVisibility(View.GONE);
                    Toast.makeText(PdfViewerActivity.this, "下載失敗", Toast.LENGTH_SHORT).show();
                });
            }
 
            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (!response.isSuccessful()) {
                    runOnUiThread(() -> {
                        progressBar.setVisibility(View.GONE);
                        Toast.makeText(PdfViewerActivity.this, "文件獲取失敗", Toast.LENGTH_SHORT).show();
                    });
                    return;
                }
 
                // 將文件保存到緩存目錄
                File file = new File(getCacheDir(), "temp.pdf");
                try (InputStream inputStream = response.body().byteStream();
                     FileOutputStream outputStream = new FileOutputStream(file)) {
                    byte[] buffer = new byte[2048];
                    int len;
                    while ((len = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, len);
                    }
                }
 
                runOnUiThread(() -> displayPdf(file));
            }
        });
    }
 
    /**
     * 使用 PDFView 顯示 PDF
     */
    private void displayPdf(File file) {
        progressBar.setVisibility(View.GONE);
        pdfView.fromFile(file)
                .defaultPage(0) // 默認打開第一頁
                .enableSwipe(true) // 允許左右滑動翻頁
                .swipeHorizontal(false) // 豎直方向翻頁
                .enableDoubletap(true) // 支持雙擊縮放
                .scrollHandle(new DefaultScrollHandle(this)) // 添加滾動條
                .spacing(10) // 頁面間距
                .load();
    }
}
 
 
// ==================== 文件：activity_pdf_viewer.xml ====================
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
 
    <com.github.barteksc.pdfviewer.PDFView
        android:id="@+id/pdfView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
 
    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:visibility="gone" />
</RelativeLayout>