从Android本机视图创建PDF文件

Question

在我们的Android应用程序中，我们有相册功能。哪些用户能够从他们的照片创建他们的专辑，之后我们希望用户能够从该专辑创建一个pdf文件。（我们在IOS中做同样的事情）

为了实现这个目标，我实施了以下解决方案。但是当我执行createPrintableFile方法时，它创建并清空pdf文件，我找不到原因？ 有没有人对它有任何想法

package com.kidokit.kidokit.helper;

import android.app.Activity;
import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Rect;
import android.graphics.pdf.PdfDocument;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.print.PrintAttributes;
import android.print.pdf.PrintedPdfDocument;
import android.support.annotation.RequiresApi;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.Toast;

import com.kidokit.kidokit.R;
import com.kidokit.kidokit.network.NetworkModels;
import com.kidokit.kidokit.ui.StorybookView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;





public class MAPdfCreator
{
    private FileOutputStream pdfFile = null;
    private String filePath = null;
    private Activity act;
    private LayoutInflater inflater;

    public MAPdfCreator(Activity act) throws FileNotFoundException
    {
        filePath = act.getFilesDir()+"/KidoKitAlbum.pdf";
        pdfFile = new FileOutputStream(filePath);
        this.act = act;
        inflater = LayoutInflater.from(this.act);
    }

    public void createPrintableFile(List<NetworkModels.GetPhotosInAlbumRes.Photo> photos) throws IOException {
        ArrayList<View> result = new ArrayList<View>();

        int index = 0;
        for (NetworkModels.GetPhotosInAlbumRes.Photo photo : photos) {
            View myImageLayout = inflater.inflate(R.layout.view_storybook, null, false);
            final StorybookView sbv = (StorybookView) myImageLayout.findViewById(R.id.sbv);
            sbv.measure(480,853);
            sbv.layout(0,0,480,853);

            if (index == 0) {
                /*
                sbv.setTemplateLayout(R.layout.view_sb_cover);
                sbv.setImage(photo.photoFile);
                sbv.setLabel(photo.photoTitle);
                sbv.setDate(photo.photoDate);
                sbv.closeEditMode();
                */
            } else {
                sbv.setTemplateLayout(photo.getLayoutResource());

                if (photo.photoFile != null && !photo.photoFile.equals("")) {
                    sbv.setImage(photo.photoFile);
                }
                if (photo.photoTitle != null) {
                    sbv.setLabel(photo.photoTitle);
                }

                if (photo.photoDate != null) {
                    sbv.setDate(photo.photoDate);
                }
                sbv.closeEditMode();


            }

            result.add(sbv);
            index++;
        }

        convertViewsToPdf(result);
    }

    public void convertViewsToPdf(ArrayList<View> views) throws IOException {
        if (Build.VERSION.SDK_INT >= 19) {

            PrintAttributes printAttrs = new PrintAttributes.Builder().
                    setColorMode(PrintAttributes.COLOR_MODE_COLOR).
                    setMediaSize(PrintAttributes.MediaSize.NA_LETTER).
                    setResolution(new PrintAttributes.Resolution("KDK_LBL", "PRINT_SERVICE", 480, 853)).
                    setMinMargins(PrintAttributes.Margins.NO_MARGINS).
                    build();
            PdfDocument document = new PdfDocument();


            int index = 0;
            for (View view : views) {
                PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(480,853,index).create();
                PdfDocument.Page page = document.startPage(pageInfo);

                view.draw(page.getCanvas());

                document.finishPage(page);
                index++;
            }

            document.writeTo(pdfFile);


            document.close();
            pdfFile.close();



            File file = new File(filePath);
            if(!file.exists()) {
                System.out.println("FILE DOES NOT EXIST");
                return;
            }

            this.openPdfFile();
        }
    }

    public void openPdfFile()
    {
        Uri path = Uri.parse("content://"+act.getPackageName()+"/"+filePath);

        Intent fileViewIntent = new Intent(Intent.ACTION_VIEW);
        fileViewIntent.setDataAndType(path, "application/pdf");
        String packageName = "com.adobe.reader";

        fileViewIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        fileViewIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

        try {
            act.startActivity(fileViewIntent);

        } catch(ActivityNotFoundException e){

            try {
                act.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("market://details?id="+packageName)));
            } catch (android.content.ActivityNotFoundException anfe) {
                act.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id="+packageName)));
            }

        } catch(Exception e){
            Toast.makeText(act, "Can not open file: (" + filePath +")", Toast.LENGTH_SHORT).show();
        }

    }
}

这是调用abow createPrintableFile方法的代码

private void printAlbum(final int albumId)
{
    NetworkManager.getPhotosInAlbum(albumId,new TokenCallback<NetworkModels.GetPhotosInAlbumRes>() {
        @Override
        public void onResponse(Call<NetworkModels.GetPhotosInAlbumRes> call, Response<NetworkModels.GetPhotosInAlbumRes> response) {
            super.onResponse(call, response);

            if (response.code() == 200) {
                if (response.body().success) {

                    NetworkModels.GetPhotosInAlbumRes result = response.body();
                    try {
                        MAPdfCreator creator = new MAPdfCreator(currrentContext);
                        creator.createPrintableFile(result.photos);
                    } catch (java.io.IOException e) {
                        e.printStackTrace();
                    }

                } else {
                    activity.progressDialog.dismiss();
                    activity.showSnackbar(activity.getText(R.string.unknown_error).toString());
                }
            } else {
                activity.showSnackbar(activity.getText(R.string.server_error).toString());
            }
        }

        @Override
        public void onFailure(Call<NetworkModels.GetPhotosInAlbumRes> call, Throwable t) {
            super.onFailure(call, t);
            activity.showSnackbar(activity.getText(R.string.connection_error).toString());
            activity.progressDialog.dismiss();
        }
    });
}