app实现预览功能

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    android:padding="@dimen/box_inset_layout_padding"
    tools:context=".activity.PdfActivity">
    <com.github.barteksc.pdfviewer.PDFView
        android:id="@+id/pdfView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
 
</androidx.constraintlayout.widget.ConstraintLayout>

package com.example.nucleicacid32.activity;
 
 
import android.graphics.Canvas;
import android.os.Bundle;
import android.os.StrictMode;
 
import com.example.nucleicacid32.base.BaseActivity;
import com.example.nucleicacid32.databinding.ActivityPdfBinding;
import com.github.barteksc.pdfviewer.listener.OnDrawListener;
import com.github.barteksc.pdfviewer.listener.OnLoadCompleteListener;
import com.github.barteksc.pdfviewer.listener.OnPageChangeListener;
import com.github.barteksc.pdfviewer.listener.OnPageErrorListener;
import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle;
 
public class PdfActivity extends BaseActivity<ActivityPdfBinding> implements OnPageChangeListener, onl oadCompleteListener, OnDrawListener, OnPageErrorListener {
        public static final String FILE_NAME = "ali.pdf";
 
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            init();
 
        }
 
        private void init() {
            if (android.os.Build.VERSION.SDK_INT > 9) {
                StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
                StrictMode.setThreadPolicy(policy);
            }
            viewBinding.pdfView.fromAsset(FILE_NAME)
                    .defaultPage(0)
                    .onPageChange(this)
                    .enableSwipe(false)
                    .enableAnnotationRendering(true)
                    .onLoad(this)
                    .scrollHandle(new DefaultScrollHandle(this))
                    .spacing(10) // in dp
                    .onPageError(this)
                    .load();
        }
 
 
        @Override
        public void onPageChanged(int page, int pageCount) {
 
        }
 
        @Override
        public void loadComplete(int nbPages) {
 
        }
 
        @Override
        public void onLayerDrawn(Canvas canvas, float pageWidth, float pageHeight, int displayedPage) {
 
        }
 
        @Override
        public void onPageError(int page, Throwable t) {
 
        }
 
 
    }