android pdf文件预览

首先需要项目里面有pdf文件，或者手机本地有pdf文件，如果只是测试可以直接引入pdf文件到项目的assets目录下，如果是服务器上的pdf需要先下载到手机本地然后使用文件路径

废话不多说，上方法

1.引入build.gradle中引入需要的包

implementation 'com.github.chrisbanes:PhotoView:2.0.0'

2.声明获取权限

1）AndrooidManifest.xml中声明权限

如果是服务器文件需要下载，还需声明网络权限

2）Android 6.0新特性，一些保护权限，除了要在AndroidManifest中声明权限，还需要在activity中使用代码动态获取权限

if (Build.VERSION.SDK_INT >= 23) {
            
             String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE,
                    Manifest.permission.INTERNET};
            //验证是否许可权限
            for (String str : permissions) {
                if (this.checkSelfPermission(str) != PackageManager.PERMISSION_GRANTED) {
                    //申请权限
                    this.requestPermissions(permissions, REQUEST_CODE_CONTACT);
                }
            }
        }

3.布局文件使用ViewPager

4.打开pdf文件读取

 public void init() {
        String FILE_NAME = getIntent().getStringExtra("path");//文件路径，根据项目需求修改
        final File file = new File(FILE_NAME);

        if (!file.exists()){
           Toast.makeText(PdfActivity.this,"文件不存在",Toast.LENGTH_SHORT).show();
        }
        mInflater = LayoutInflater.from(this);
        vpPdf =findViewById(R.id.vp_pdf);

        try {
            openRender();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void openRender() throws IOException {

        File file = new File(FILE_NAME);
        if (!file.exists()) {
            //复制文件到本地存储
            InputStream asset = getAssets().open(FILE_NAME);
            FileOutputStream fos = new FileOutputStream(file);
            byte[] buffer = new byte[1024];

            int size;
            while ((size = asset.read(buffer)) != -1) {
                fos.write(buffer, 0, size);
            }

            asset.close();
            fos.close();
        }

        //初始化PdfRender
        mDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
        if (mDescriptor != null) {
            mRenderer = new PdfRenderer(mDescriptor);
        }

        //初始化ViewPager的适配器并绑定
        MyAdapter adapter = new MyAdapter();
        vpPdf.setAdapter(adapter);
    }

class MyAdapter extends PagerAdapter {

        @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
        @Override
        public int getCount() {
            return mRenderer.getPageCount();
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view==object;
        }

        @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            View view = mInflater.inflate(R.layout.item_pdf, null);

            PhotoView pvPdf = view.findViewById(R.id.iv_pdf);
            pvPdf.setEnabled(true);

            if (getCount() <= position) {
                return view;
            }

            PdfRenderer.Page currentPage = mRenderer.openPage(position);
            Bitmap bitmap = Bitmap.createBitmap(1080, 1760, Bitmap.Config
                    .ARGB_8888);
            currentPage.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
            pvPdf.setImageBitmap(bitmap);
            //关闭当前Page对象
            currentPage.close();

            container.addView(view);
            return view;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            //销毁需要销毁的视图
            container.removeView((View) object);
        }
    }

 5.关闭pdf文件读取，一般activity销毁时需要使用

@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
private void closeRenderer() throws IOException {
    if (mRenderer != null){
        mRenderer.close();
    }
    if (mDescriptor != null){
        mDescriptor.close();
    }


}

以上就是pdf文件读取的全流程