Java 如何从多个图像中生成PDF

我正在构建一个应用程序，将图像上传到我的公司服务器 我现在正在拍摄多幅图像，并将其转换为PDF格式，以便同一文档中的图像可以保持在一起

我的问题是我不知道如何制作，这样我就可以将多个图像添加到PDF创建中 我正在使用Kosal Geek的android库PhotoUtils进行图像处理 和PDFdocument来创建pdf

目前，单个图像可以工作，但如果我选择多个图像，就会出现空指针异常

主代码

public class PdfMake extends AppCompatActivity {
    private final int PICK_IMAGE=12345;
    private final int REQUEST_CAMERA=6352;
    CameraPhoto cameraPhoto;
    GalleryPhoto galleryPhoto;
    String selectedPhoto;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        StrictMode.VmPolicy.Builder builder4=new StrictMode.VmPolicy.Builder();
        StrictMode.setVmPolicy(builder4.build());
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_make);
        Button fromCamera=findViewById(R.id.SelectImages2);
        Button PdfMake=findViewById(R.id.button4);

        fromCamera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPictureDialog();
            }
        });
        PdfMake.setOnClickListener(new View.OnClickListener() {
            @RequiresApi(api=Build.VERSION_CODES.KITKAT)
            @Override
            public void onClick(View v) {
                try {
                    createPdf();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
        private void showPictureDialog () {
            AlertDialog.Builder pictureDialog=new AlertDialog.Builder(this);
            pictureDialog.setTitle("Select Action");
            String[] pictureDialogItems={
                    "Select photo from gallery",
                    "Capture photo from camera"};
            pictureDialog.setItems(pictureDialogItems,
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            switch (which) {
                                case 0:
                                    getImageFromGallery();
                                    break;
                                case 1:
                                    try {
                                        getImageFromCamera();
                                    } catch (IOException e) {
                                        e.printStackTrace();
                                    }
                                    break;

                            }
                        }
                    });

        }




    @RequiresApi(api=Build.VERSION_CODES.KITKAT)
    private void createPdf() throws IOException {
        // create a new document
        PdfDocument document=new PdfDocument();
        // crate a page description
        PdfDocument.PageInfo pageInfo=new PdfDocument.PageInfo.Builder(3000, 6000, 1).create();
        // start a page
        PdfDocument.Page page=document.startPage(pageInfo);
        Canvas canvas=page.getCanvas();
        Bitmap image=BitmapFactory.decodeFile(selectedPhoto);
        canvas.drawBitmap(image, 10, 10, null);

        document.finishPage(page);
        String directory_path=Environment.getExternalStorageDirectory().getPath() + "/mypdf/";
        File file=new File(directory_path);
        if (!file.exists()) {
            file.mkdirs();
        }
        String targetPdf=directory_path + "test-2.pdf";
        File filePath=new File(targetPdf);
        try {
            document.writeTo(new FileOutputStream(filePath));
            Toast.makeText(this, "Done", Toast.LENGTH_LONG).show();
        } catch (IOException e) {
            Log.e("main", "error " + e.toString());
            Toast.makeText(this, "Something wrong: " + e.toString(), Toast.LENGTH_LONG).show();
        }
        // close the document
        document.close();
    }



        private void getImageFromCamera () throws IOException {

            cameraPhoto=new CameraPhoto(getApplicationContext());
            Intent in=cameraPhoto.takePhotoIntent();
            startActivityForResult(in, REQUEST_CAMERA);
            Bungee.split(PdfMake.this);

        }

        private void getImageFromGallery () {

        Intent intent=new Intent();
            intent.setType("image/*");
            intent.setAction(Intent.ACTION_GET_CONTENT);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
                intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
            }
            if (intent.resolveActivity(getPackageManager()) != null) {
                startActivityForResult(Intent.createChooser(intent, "Select Picture"), PICK_IMAGE);
                Bungee.split(PdfMake.this);

            }
        }


protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_OK) {
        if (requestCode == REQUEST_CAMERA) {


        String photoPath=cameraPhoto.getPhotoPath();
        selectedPhoto=photoPath;
        try {
        Bitmap bitmap=ImageLoader.init().from(photoPath).requestSize(512, 512).getBitmap();
        } catch (FileNotFoundException e) {
        Toasty.error(getApplicationContext(),
        "Something Wrong while loading photos", Toast.LENGTH_SHORT).show();
        }

        } else if (requestCode == PICK_IMAGE) {
        Uri uri=data.getData();

        galleryPhoto.setPhotoUri(uri);
        String photoPath=galleryPhoto.getPath();
        selectedPhoto=photoPath;
        try {
        Bitmap bitmap=ImageLoader.init().from(photoPath).requestSize(512, 512).getBitmap();
        } catch (FileNotFoundException e) {
        Toasty.error(getApplicationContext(),
        "Something Wrong while choosing photos", Toast.LENGTH_SHORT).show();
        }
        }
        }
        }
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        int CAMERA_RESULT=11100;
        if(requestCode == CAMERA_RESULT){
        if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED){
        try {
        getImageFromCamera();
        } catch (IOException e) {
        e.printStackTrace();
        }
        }
        else{
        Toasty.error(getApplicationContext(), "Permission Needed.", Toast.LENGTH_LONG).show();
        }
        }
        else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
        if(requestCode == PICK_IMAGE){
        if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED){
        getImageFromGallery();
        }
        else{
        Toasty.error(getApplicationContext(), "Permission Needed.", Toast.LENGTH_LONG).show();
        }
        }
        else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
        }
}

画廊图片代码

public class GalleryPhoto {
    final String TAG = this.getClass().getSimpleName();
    private Context context;
    private Uri photoUri;

    public void setPhotoUri(Uri photoUri) {
        this.photoUri = photoUri;
    }

    public GalleryPhoto(Context context) {
        this.context = context;
    }

    public Intent openGalleryIntent() {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction("android.intent.action.GET_CONTENT");
        return Intent.createChooser(intent, this.getChooserTitle());
    }

    public String getChooserTitle() {
        return "Select Pictures";
    }

    public String getPath() {
        String path;
        if (VERSION.SDK_INT < 11) {
            path = RealPathUtil.getRealPathFromURI_BelowAPI11(this.context, this.photoUri);
        } else if (VERSION.SDK_INT < 19) {
            path = RealPathUtil.getRealPathFromURI_API11to18(this.context, this.photoUri);
        } else {
            path = RealPathUtil.getRealPathFromURI_API19(this.context, this.photoUri);
        }

        return path;
    }
}

---

有一个很好的图书馆叫

您要做的是创建一个PDF对象和其中的一个页面

PDFWriter mPDFWriter = new PDFWriter(PaperSize.FOLIO_WIDTH, PaperSize.FOLIO_HEIGHT);

然后，您可以通过

addImage

向其添加图像，并通过

newPage（）

---

您可以在项目中看到演示。

相关：如何将此库与我的应用程序集成，我找不到库的.JAR文件。。我真的不知道；我不知道如何添加一个不在JAR文件中的库。有什么建议吗？我没有注意到这个库很旧。你可以下载它并在本地编译，但你可能会陷入混乱。另一种选择是将文件复制到项目中，并与项目一起编译。这意味着你将没有图书馆。最后，我在这里找到了一个JAR文件：谢谢，不管怎样，这个库很古老，就像你说的，我正陷入一个渐进的混乱和不推荐的依赖等等。我将尝试遵循PDFdocuments官方android开发教程，也许我可以从那里学到一些东西

PDFWriter mPDFWriter = new PDFWriter(PaperSize.FOLIO_WIDTH, PaperSize.FOLIO_HEIGHT);