Android本地浏览PDF（Android PDF.js 简要学习手册）

环境

Min SDK: 21

依赖：

implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1"
implementation "androidx.webkit:webkit:1.12.0"

权限：

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

下载pdf.js :https://github.com/mozilla/pdf.js/tree/v2.10.377/web

引入步骤

app/src/main/assets/pdfjs/
├── web/
│   ├── viewer.html
│   ├── viewer.js
│   └── ...
├── build/
│   ├── pdf.js
│   ├── pdf.worker.js
│   └── ...

实现

import android.content.Context
import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.view.WindowManager
import android.webkit.WebChromeClient
import android.webkit.WebResourceRequest
import android.webkit.WebView
import android.webkit.WebViewClient
import androidx.core.content.ContextCompat
import androidx.webkit.WebViewAssetLoader
import com.gyf.immersionbar.ImmersionBar
import com.sunward.markettools.R
import com.sunward.markettools.base.BaseActivity
import com.sunward.markettools.databinding.ActivityWebviewBinding
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.MainScope
import kotlinx.coroutines.cancel
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import java.io.File
import java.io.FileOutputStream
import java.net.URL
import java.net.URLEncoder
import java.nio.channels.Channels

/**
 *@dateTime:2025/4/29
 *@作者：MaoYoung
 */
class WebViewPDFActivity : BaseActivity<MarketViewModel, ActivityWebviewBinding>(
    R.layout.activity_webview
) {
    companion object {
        fun newInstance(activity: Context?, url: String, fileName: String) {
            activity?.startActivity(Intent(activity, WebViewPDFActivity::class.java).apply {
                putExtra(activity.getString(R.string.params_web_url), url)
                putExtra(activity.getString(R.string.params_file_name), fileName)
            })
        }
    }

    private val coroutineScope = MainScope()
    private val domain = "appassets.androidplatform.net"
    override fun initView(savedInstanceState: Bundle?) {
        val pdfUrl =
            intent.getStringExtra(getString(R.string.params_web_url)) ?: ""
        val fileName = intent.getStringExtra(getString(R.string.params_file_name)) ?: ""
        window.setFlags(
            WindowManager.LayoutParams.FLAG_SECURE,
            WindowManager.LayoutParams.FLAG_SECURE
        )
        mBinding.apply {
            tvTitle.text = fileName
            toolbar.setNavigationOnClickListener { finishActivity() }
        }

        val downloadDir = saveDownloadFilePath()

        val assetLoader = WebViewAssetLoader.Builder()
            .setDomain(domain)
            .addPathHandler("/assets/", WebViewAssetLoader.AssetsPathHandler(this))
            .addPathHandler(
                "/Download/",
                WebViewAssetLoader.InternalStoragePathHandler(this, downloadDir)
            )
            .build()
        mBinding.apply {
            webview.apply {
                settings.apply {
                    javaScriptEnabled = true
                    domStorageEnabled = true
                    allowFileAccess = false // 不再需要 file 访问
                }
                //设置WebViewClient与AssetLoader
                webViewClient = object : WebViewClient() {
                    override fun shouldInterceptRequest(
                        view: WebView?,
                        request: WebResourceRequest?
                    ): android.webkit.WebResourceResponse? {
                        return assetLoader.shouldInterceptRequest(request?.url!!)
                    }

                    override fun shouldOverrideUrlLoading(
                        view: WebView?,
                        request: WebResourceRequest?
                    ): Boolean {
                        return super.shouldOverrideUrlLoading(view, request)
                    }

                    override fun onPageFinished(view: WebView?, url: String?) {
                        view?.loadUrl(
                            "javascript:(function() {" +
                                    "var rightToolbar = document.getElementById('toolbarViewerRight');" +
                                    "if (rightToolbar) { rightToolbar.style.display = 'none'; }" +
                                    "})()"
                        )
                    }

                    override fun onReceivedError(
                        view: WebView?,
                        errorCode: Int,
                        description: String?,
                        failingUrl: String?
                    ) {
                        Log.e("WebViewActivity", "Error: $description, URL: $failingUrl")
                    }
                }

                webChromeClient = WebChromeClient()


                downloadAndDisplayPdf(pdfUrl, fileName)
            }
        }
    }

    private fun saveDownloadFilePath(): File {
        val downloadDir = File(this.filesDir, "Download")
        if (!downloadDir.exists()) {
            downloadDir.mkdirs()
        }
        return downloadDir
    }

    private fun downloadAndDisplayPdf(pdfUrl: String, fileName: String) {
        coroutineScope.launch {
            try {
                val finalFileName = if (fileName.endsWith(".pdf")) fileName else "$fileName.pdf"

                val downloadedFileName =
                    withContext(Dispatchers.IO) {
                        val downloadDir = saveDownloadFilePath()
                        val file = File(downloadDir, finalFileName)
                        if (file.exists()) file.delete()
                        val url = URL(pdfUrl)
                        val connection = url.openConnection()
                        connection.connect()
                        val inputStream = connection.getInputStream()
                        FileOutputStream(file).use { output ->
                            Channels.newChannel(inputStream).use { inputChannel ->
                                output.channel.use { outputChannel ->
                                    outputChannel.transferFrom(inputChannel, 0, Long.MAX_VALUE)
                                }
                            }
                        }
                        finalFileName
                    }

                val encodedPath = URLEncoder.encode("$downloadedFileName", "UTF-8")
                val viewerUrl =
                    "https://$domain/assets/pdfjs/web/viewer.html?file=%2FDownload%2F$encodedPath"
                mBinding.webview.loadUrl(viewerUrl)
            } catch (e: Exception) {
                e.printStackTrace()
                val encodedUrl = try {
                    URLEncoder.encode(pdfUrl, "UTF-8")
                } catch (e: Exception) {
                    pdfUrl
                }
                val fallbackUrl = "file:///android_asset/pdfjs/web/viewer.html?file=$encodedUrl"
                mBinding.webview.loadUrl(fallbackUrl)
            }
        }
    }


    override fun onResume() {
        super.onResume()
        mBinding.webview.onResume()
    }

    override fun onPause() {
        super.onPause()
        mBinding.webview.onPause()
    }

    override fun onDestroy() {
        mBinding.webview.destroy()
        coroutineScope.cancel()
        super.onDestroy()
    }

    override fun initImmersionBar() {
        ImmersionBar.with(this)
            .statusBarColorTransformEnable(false)
            .keyboardEnable(false)
            .statusBarDarkFont(true)
            .navigationBarDarkIcon(true)
            .fitsSystemWindowsInt(true, ContextCompat.getColor(this, R.color.color_fa))
            .navigationBarColor(R.color.color_fa)
            .init()
    }
}

WebViewActivity.newInstance(context, "这里传递下载PDF的地址")

工作原理

1. 初始化

   • 从intent中获取PDF 的URL
   • 配置域名： .setDomain(domain)

2. 下载

   使用协成下载到/Download/文件夹中

3. 显示

   将文件加载到本地PDF路径（file://.../temp.pdf）的"https://$domain/assets/pdfjs/web/viewer.html