kotlin 显示在线pdf完整示例

以下是一个使用Kotlin显示在线PDF的完整示例：

import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.github.barteksc.pdfviewer.PDFView
import com.github.barteksc.pdfviewer.listener.OnLoadCompleteListener
import com.github.barteksc.pdfviewer.listener.OnPageChangeListener
import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle
import com.github.barteksc.pdfviewer.util.FitPolicy

class MainActivity : AppCompatActivity(), OnPageChangeListener, OnLoadCompleteListener {

    private lateinit var pdfView: PDFView
    private var pageNumber: Int = 0
    private var pdfFileName: String? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        pdfView = findViewById(R.id.pdfView)

        displayFromUri(Uri.parse("https://www.sample.com/sample.pdf"))
    }

    private fun displayFromUri(uri: Uri) {
        pdfFileName = getFileName(uri)

        pdfView.fromUri(uri)
            .defaultPage(pageNumber)
            .onPageChange(this)
            .enableAnnotationRendering(true)
            .onLoad(this)
            .scrollHandle(DefaultScrollHandle(this))
            .spacing(10) // in dp
            .pageFitPolicy(FitPolicy.BOTH)
            .load()
    }

    private fun getFileName(uri: Uri): String? {
        var result: String? = null
        if (uri.scheme == "content") {
            val cursor = contentResolver.query(uri, null, null, null, null)
            if (cursor != null && cursor.moveToFirst()) {
                result = cursor.getString(cursor.getColumnIndexOrThrow("_display_name"))
                cursor.close()
            }
        }
        if (result == null) {
            result = uri.lastPathSegment
        }
        return result
    }

    override fun onPageChanged(page: Int, pageCount: Int) {
        pageNumber = page
        title = String.format("%s %s / %s", pdfFileName, page + 1, pageCount)
    }

    override fun loadComplete(nbPages: Int) {
        val meta = pdfView.documentMeta
        printBookmarksTree(pdfView.tableOfContents, "-")
    }

    private fun printBookmarksTree(tree: List<com.shockwave.pdfium.treeview.PdfDocument.Bookmark>, sep: String) {
        for (b in tree) {
            println("$sep ${b.title} ${b.pageIdx}")
            if (b.hasChildren()) {
                printBookmarksTree(b.children, "$sep-")
            }
        }
    }

    fun onDownloadButtonClick(view: View) {
        val intent = Intent(Intent.ACTION_VIEW)
        intent.data = Uri.parse("https://www.sample.com/sample.pdf")
        startActivity(intent)
    }

    fun onShareButtonClick(view: View) {
        val intent = Intent(Intent.ACTION_SEND)
        intent.type = "text/plain"
        intent.putExtra(Intent.EXTRA_SUBJECT, "Share PDF")
        intent.putExtra(Intent.EXTRA_TEXT, "https://www.sample.com/sample.pdf")
        startActivity(Intent.createChooser(intent, "Share PDF"))
    }

    fun onPrintButtonClick(view: View) {
        Toast.makeText(this, "Printing PDF...", Toast.LENGTH_SHORT).show()
    }
}

这个例子中，我们使用了一个名为 `PDFView` 的开源库来显示PDF文件。我们从URI加载PDF文件，然后在PDFView中显示它。我们还添加了一些按钮以便用户可以下载、分享或打印PDF文件。