依赖

implementation 'com.squareup.okhttp3:okhttp:4.9.1'
implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'

在project.build中添加该源

maven { url "https://repository.liferay.com/nexus/content/repositories/public/" }

XML

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.github.barteksc.pdfviewer.PDFView
        android:id="@+id/pdfView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

Activity

import android.os.Bundle;
import android.os.Environment;
import androidx.appcompat.app.AppCompatActivity;
import com.github.barteksc.pdfviewer.PDFView;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class MainActivity extends AppCompatActivity {

    private PDFView pdfView;
    private static final String PDF_URL = "https://www.example.com/sample.pdf"; // 替换为你的 PDF URL

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

        pdfView = findViewById(R.id.pdfView);
        downloadAndDisplayPdf(PDF_URL);
    }

    private void downloadAndDisplayPdf(String url) {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(url).build();

        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                e.printStackTrace();
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {
                    File pdfFile = new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), "downloaded.pdf");
                    try (InputStream inputStream = response.body().byteStream();
                         FileOutputStream outputStream = new FileOutputStream(pdfFile)) {

                        byte[] buffer = new byte[2048];
                        int length;
                        while ((length = inputStream.read(buffer)) != -1) {
                            outputStream.write(buffer, 0, length);
                        }

                        // 在主线程中加载 PDF
                        runOnUiThread(() -> pdfView.fromFile(pdfFile).load());
                    }
                }
            }
        });
    }
}

PDF不支持在线预览，因此要先下载后加载

•	下载 PDF 文件：使用 OkHttp 请求 PDF 的在线地址，并将其保存到设备的下载目录中。
•	加载 PDF 文件：下载完成后，通过 pdfView.fromFile(pdfFile).load() 在 PDFView 中显示 PDF 文件。