Android实现打开本地pdf文件的两种方式

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

<!-- AndroidManifest.xml -->
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.pdfopener">
 
    <!-- 申请读取外部存储权限 -->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
 
    <application
        android:allowBackup="true"
        android:label="PDFOpener"
        android:icon="@mipmap/ic_launcher"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:theme="@style/AppTheme">
        
        <!-- 主Activity -->
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        
        <!-- 配置FileProvider -->
        <provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="${applicationId}.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths"/>
        </provider>
        
    </application>
</manifest>

<!-- res/xml/file_paths.xml -->
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 允许访问外部存储中指定目录下的所有文件 -->
    <external-path name="external_files" path="."/>
</paths>

package com.example.pdfopener;
 
import android.Manifest;
import android.content.ActivityNotFoundException;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.widget.Button;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.FileProvider;
import java.io.File;
 
/**
 * MainActivity
 *
 * 该Activity展示如何利用Intent从本地打开PDF文件，
 * 使用FileProvider获取content:// URI，并调用系统PDF阅读器。
 */
public class MainActivity extends AppCompatActivity {
 
    private static final int REQUEST_READ_STORAGE = 100;
    private Button btnOpenPDF;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_pdf);
 
        btnOpenPDF = findViewById(R.id.btn_open_pdf);
 
        // 检查READ_EXTERNAL_STORAGE权限
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                    REQUEST_READ_STORAGE);
        }
 
        btnOpenPDF.setOnClickListener(v -> {
            // 此处假设PDF文件位于外部存储的Download目录下，文件名为sample.pdf
            File pdfFile = new File(Environment.getExternalStoragePublicDirectory(
                    Environment.DIRECTORY_DOWNLOADS), "sample.pdf");
 
            if (!pdfFile.exists()) {
                Toast.makeText(MainActivity.this, "PDF文件不存在", Toast.LENGTH_SHORT).show();
                return;
            }
 
            // 通过FileProvider获取content URI
            Uri pdfUri = FileProvider.getUriForFile(MainActivity.this,
                    getApplicationContext().getPackageName() + ".fileprovider", pdfFile);
 
            // 创建Intent，设置类型为application/pdf
            Intent intent = new Intent(Intent.ACTION_VIEW);
            intent.setDataAndType(pdfUri, "application/pdf");
            // 授权临时读取权限
            intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
 
            try {
                startActivity(intent);
            } catch (ActivityNotFoundException e) {
                Toast.makeText(MainActivity.this, "未找到可以打开PDF的应用，请安装PDF阅读器", Toast.LENGTH_LONG).show();
            }
        });
    }
 
    /**
     * 动态请求权限回调
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        if (requestCode == REQUEST_READ_STORAGE) {
            if (!(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)) {
                Toast.makeText(this, "需要授予存储读取权限", Toast.LENGTH_LONG).show();
            }
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

<!-- res/layout/activity_main_pdf.xml -->
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/main_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center"
    android:padding="16dp">
 
    <Button
        android:id="@+id/btn_open_pdf"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="打开本地PDF文件" />
</LinearLayout>

dependencies {
    // 其他依赖...
    implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'
}

allprojects {
    repositories {
        google()
        jcenter()
        maven { url 'https://jitpack.io' }
    }
}

<!-- res/layout/activity_pdf_viewer.xml -->
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pdf_container"
    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" />
</RelativeLayout>

package com.example.pdfopener;
 
import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import com.github.barteksc.pdfviewer.PDFView;
import java.io.File;
 
/**
 * PDFViewerActivity
 *
 * 该Activity展示如何利用AndroidPdfViewer库在应用内部加载和展示本地PDF文件。
 */
public class PDFViewerActivity extends AppCompatActivity {
 
    private static final int REQUEST_READ_STORAGE = 101;
    private PDFView pdfView;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_viewer);
 
        pdfView = findViewById(R.id.pdfView);
 
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                    REQUEST_READ_STORAGE);
        } else {
            loadPdf();
        }
    }
 
    private void loadPdf() {
        // 假设PDF文件位于Download目录下，文件名为sample.pdf
        File pdfFile = new File(Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_DOWNLOADS), "sample.pdf");
 
        if (!pdfFile.exists()) {
            Toast.makeText(PDFViewerActivity.this, "PDF文件不存在", Toast.LENGTH_SHORT).show();
            return;
        }
 
        // 使用PDFView加载PDF文件
        pdfView.fromFile(pdfFile)
                .enableSwipe(true)          // 支持滑动翻页
                .swipeHorizontal(false)     // false为竖直滑动
                .enableDoubletap(true)      // 支持双击缩放
                .defaultPage(0)             // 默认第一页
                .load();
    }
 
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        if (requestCode == REQUEST_READ_STORAGE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                loadPdf();
            } else {
                Toast.makeText(this, "需要读取存储权限以打开PDF文件", Toast.LENGTH_LONG).show();
            }
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}