Android download pdf file from url and save to internal storage GitHub

1,Integrate PDF Viewer Library in Gradle file.

implementation ‘com.github.barteksc:android-pdf-viewer:2.8.2’

2,Design Screen as Per Requirement.

<LinearLayout
 android:layout_width=”match_parent”
 android:layout_height=”match_parent”
 android:orientation=”vertical”><com.github.barteksc.pdfviewer.PDFView
 android:id=”@+id/pdfView”
 android:layout_width=”match_parent”
 android:layout_height=”match_parent” /></LinearLayout>

3,Download PDF and View File in PDF viewer.

`public class PdfViewActivity extends AppCompatActivity { 
    ActivityPdfviewBinding binding; 
    ProgressDialog mProgressDialog; 
    public Context context; 
    public String samplePDF = "http://www.africau.edu/images/default/sample.pdf"; 
    public static final int PERMISSIONS_MULTIPLE_REQUEST_CERTIFICATE = 123;
    @Override  protected void onCreate(@Nullable Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        binding = DataBindingUtil.setContentView(this, R.layout.activity_pdfview); 
        context = PdfViewActivity.this;
        mProgressDialog = new ProgressDialog(context);
        checkAndroidVersionCertificate();
    }
    private void downloadFile() { 
        mProgressDialog.show(); 
        mProgressDialog.setMessage("downloading"); 
        mProgressDialog.setMax(100); 
        mProgressDialog.setIndeterminate(true); 
        mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); 
        mProgressDialog.setCancelable(true); 
        DownloadFileTask task = new DownloadFileTask( PdfViewActivity.this,  samplePDF,  "/download/pdf_file.pdf"); 
        task.startTask(); 
    }
    public class DownloadFileTask { 
        public static final String TAG = "DownloadFileTask";
        private PdfViewActivity context; 
        private GetTask contentTask; 
        private String url; 
        private String fileName;
        public DownloadFileTask(PdfViewActivity context, String url, String fileName) { 
            this.context = context; 
            this.url = url; 
            this.fileName = fileName; 
        }
        public void startTask() { 
            doRequest(); 
        }
        private void doRequest() { 
            contentTask = new GetTask(); 
            contentTask.execute(); 
        }
        private class GetTask extends AsyncTask < String, Integer, String > {
            @Override  protected String doInBackground(String… arg0) { 
                int count; 
                try { 
                    URL _url = new URL(url); 
                    URLConnection conection = _url.openConnection(); 
                    conection.connect(); 
                    String extension = url.substring(url.lastIndexOf('.') + 1).trim(); 
                    InputStream input = new BufferedInputStream(_url.openStream(),  8192); 
                    OutputStream output = new FileOutputStream( Environment.getExternalStorageDirectory() + fileName); 
                    byte data[] = new byte[1024]; 
                    while ((count = input.read(data))  != -1) { 
                        output.write(data, 0, count); 
                    } 
                    output.flush(); 
                    output.close(); 
                    input.close(); 
                } catch (Exception e) { 
                    Log.e("Error: ", e.getMessage()); 
                } 
                return null; 
            }
            protected void onPostExecute(String data) { 
                context.onFileDownloaded(); 
            } 
        } 
    }
    public void onFileDownloaded() {
        if (mProgressDialog.isShowing()) { 
            mProgressDialog.dismiss(); 
        }
        File file = new File(Environment.getExternalStorageDirectory() .getAbsolutePath()  + "/download/pdf_file.pdf"); 
        if (file.exists()) { 
            binding.pdfView.fromFile(file)  //.pages(0, 2, 1, 3, 3, 3) // all pages are displayed by default
                 .enableSwipe(true) .swipeHorizontal(true) .enableDoubletap(true) .defaultPage(0) .enableAnnotationRendering(true) .password(null) .scrollHandle(null) .onLoad(new OnLoadCompleteListener() { 
                    @Override  public void loadComplete(int nbPages) { 
                        binding.pdfView.setMinZoom(1 f); 
                        binding.pdfView.setMidZoom(5 f); 
                        binding.pdfView.setMaxZoom(10 f); 
                        binding.pdfView.zoomTo(2 f); 
                        binding.pdfView.scrollTo(100, 0); 
                        binding.pdfView.moveTo(0 f, 0 f); 
                    } 
                }) .load();
        } 
    }
    @RequiresApi(api = Build.VERSION_CODES.M)  private void checkPermission_Certificate() { 
        if (ContextCompat.checkSelfPermission(context,  Manifest.permission.READ_EXTERNAL_STORAGE) + ContextCompat .checkSelfPermission(context,  Manifest.permission.WRITE_EXTERNAL_STORAGE)  != PackageManager.PERMISSION_GRANTED) {
            if (ActivityCompat.shouldShowRequestPermissionRationale ((Activity) context, Manifest.permission.READ_EXTERNAL_STORAGE) ||  ActivityCompat.shouldShowRequestPermissionRationale ((Activity) context, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                requestPermissions( new String[] {
                    Manifest.permission .READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE
                },  PERMISSIONS_MULTIPLE_REQUEST_CERTIFICATE); 
            } else { 
                requestPermissions( new String[] {
                    Manifest.permission .READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE
                },  PERMISSIONS_MULTIPLE_REQUEST_CERTIFICATE); 
            } 
        } else {  // write your logic code if permission already granted
            if (!samplePDF.equalsIgnoreCase("")) { 
                downloadFile(); 
            } 
        }
    }
    private void checkAndroidVersionCertificate() { 
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
            checkPermission_Certificate(); 
        } else {
            if (!samplePDF.equalsIgnoreCase("")) { 
                downloadFile(); 
            } 
        } 
    }
    @Override  public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { 
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case PERMISSIONS_MULTIPLE_REQUEST_CERTIFICATE:
                if (grantResults.length > 0) { 
                    boolean writePermission = grantResults[1] == PackageManager.PERMISSION_GRANTED; 
                    boolean readExternalFile = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                    if (writePermission && readExternalFile) {
                        if (!samplePDF.equalsIgnoreCase("")) { 
                            downloadFile();
                        }
                    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
                        if (Build.VERSION.SDK_INT >= 23 &&  !shouldShowRequestPermissionRationale(permissions[0])) { 
                            Intent intent = new Intent(); 
                            intent.setAction(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS); 
                            Uri uri = Uri.fromParts("package", getPackageName(), null); 
                            intent.setData(uri); 
                            startActivity(intent); 
                        } else { 
                            requestPermissions( new String[] {
                                Manifest.permission .READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE
                            },  PERMISSIONS_MULTIPLE_REQUEST_CERTIFICATE); 
                        } 
                    } 
                } 
                break;
        }
    }
}`

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