使用intent打开assets文件夹中的文件

Question

Hello I am tring to open a .pdf file present in a file using an intent but it is giving me 2 errors on the following line

File file = new File(getContext().getAssets().open("assets/test.pdf"));

Errors
1.Unhandled java.IO.Exception.
2. getAssets() may produce java.lang.NullPointerException
Here us the code in a fragment

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    if (position == 0) {
        File file = new File(getContext().getAssets().open("assets/test.pdf"));
        if (file .exists())
        {
            Uri path = Uri.fromFile(file );
            Intent pdfIntent = new Intent(Intent.ACTION_VIEW);
            pdfIntent.setDataAndType(path , "application/pdf");
            pdfIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            try
            {
                startActivity(pdfIntent ); }
            catch (ActivityNotFoundException e)
            {
                Toast.makeText(getActivity(), "Please install a pdf file viewer",
                        Toast.LENGTH_LONG).show();
            }
        }
}
}

Answer 1

    File fileBrochure = new File(Environment.getExternalStorageDirectory() + "/" + "abc.pdf");
    if (!fileBrochure.exists())
    {
         CopyAssetsbrochure();
    } 

    /** PDF reader code */
    File file = new File(Environment.getExternalStorageDirectory() + "/" + "abc.pdf");      

    Intent intent = new Intent(Intent.ACTION_VIEW);
    intent.setDataAndType(Uri.fromFile(file),"application/pdf");
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    try 
    {
        getApplicationContext().startActivity(intent);
    } 
    catch (ActivityNotFoundException e) 
    {
         Toast.makeText(SecondActivity.this, "NO Pdf Viewer", Toast.LENGTH_SHORT).show();
    }
}

//method to write the PDFs file to sd card
    private void CopyAssetsbrochure() {
        AssetManager assetManager = getAssets();
        String[] files = null;
        try 
        {
            files = assetManager.list("");
        } 
        catch (IOException e)
        {
            Log.e("tag", e.getMessage());
        }
        for(int i=0; i<files.length; i++)
        {
            String fStr = files[i];
            if(fStr.equalsIgnoreCase("abc.pdf"))
            {
                InputStream in = null;
                OutputStream out = null;
                try 
                {
                  in = assetManager.open(files[i]);
                  out = new FileOutputStream(Environment.getExternalStorageDirectory() + "/" + files[i]);
                  copyFile(in, out);
                  in.close();
                  in = null;
                  out.flush();
                  out.close();
                  out = null;
                  break;
                } 
                catch(Exception e)
                {
                    Log.e("tag", e.getMessage());
                } 
            }
        }
    }

 private void copyFile(InputStream in, OutputStream out) throws IOException {
        byte[] buffer = new byte[1024];
        int read;
        while((read = in.read(buffer)) != -1){
          out.write(buffer, 0, read);
        }

You cannot open the pdf file directly from the assets folder.You first have to write the file to sd card from assets folder and then read it from sd card

Answer 2

try with the file provider

 Intent intent = new Intent(Intent.ACTION_VIEW);

    // set flag to give temporary permission to external app to use your FileProvider
    intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

    // generate URI, I defined authority as the application ID in the Manifest, the last param is file I want to open
    String uri = FileProvider.getUriForFile(this, BuildConfig.APPLICATION_ID, file);

    // I am opening a PDF file so I give it a valid MIME type
    intent.setDataAndType(uri, "application/pdf");

    // validate that the device can open your File!
    PackageManager pm = getActivity().getPackageManager();
    if (intent.resolveActivity(pm) != null) {
        startActivity(intent);
    }

Answer 3

To serve a file from assets to another app you need to use a provider.

Google for the StreamProvider of CommonsWare.