Read a pdf file from assets folder

Try this

public class SampleActivity extends Activity
    {

        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            CopyReadAssets();

        }

        private void CopyReadAssets()
        {
            AssetManager assetManager = getAssets();

            InputStream in = null;
            OutputStream out = null;
            File file = new File(getFilesDir(), "abc.pdf");
            try
            {
                in = assetManager.open("abc.pdf");
                out = openFileOutput(file.getName(), Context.MODE_WORLD_READABLE);

                copyFile(in, out);
                in.close();
                in = null;
                out.flush();
                out.close();
                out = null;
            } catch (Exception e)
            {
                Log.e("tag", e.getMessage());
            }

            Intent intent = new Intent(Intent.ACTION_VIEW);
            intent.setDataAndType(
                    Uri.parse("file://" + getFilesDir() + "/abc.pdf"),
                    "application/pdf");

            startActivity(intent);
        }

        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);
            }
        }

    }

Make sure to include

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

in manifest

You can do it like this (tested and working on API 27)

Step 1

Add following dependency in your app gradle:

implementation 'com.github.barteksc:android-pdf-viewer:2.8.2'

Step 2

Add following XML code:

<com.github.barteksc.pdfviewer.PDFView
         android:id="@+id/pdfv"
         android:layout_width="match_parent"
         android:layout_height="match_parent"> 
</com.github.barteksc.pdfviewer.PDFView>

Step 3

Add following code in your java file:

public class MainActivity extends AppCompatActivity {

    PDFView pdfView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pdfView=findViewById(R.id.pdfv);
        pdfView.fromAsset("filename.pdf").load();
    }
}

These changes will load a PDF file on creation of your activity.

Though this has been answered, I wanted to share my solution as I think it is a bit easier to include.

Usage:

new OpenLocalPDF(context, 'nameOfPDFStoredInAssets').execute()

And here is the OpenLocalPDF class:

public class OpenLocalPDF {

    private static String TAG = OpenLocalPDF.class.getSimpleName();

    private WeakReference<Context> contextWeakReference;
    private String fileName;

    public OpenLocalPDF(Context context, String fileName) {
        this.contextWeakReference = new WeakReference<>(context);
        this.fileName = fileName.endsWith("pdf") ? fileName : fileName + ".pdf";
    }

    public void execute() {

        Context context = contextWeakReference.get();
        if (context != null) {
            new CopyFileAsyncTask().execute();
        }

    }


    private class CopyFileAsyncTask extends AsyncTask<Void, Void, File> {


        final String appDirectoryName = BuildConfig.APPLICATION_ID;
        final File fileRoot = new File(Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_DOCUMENTS), appDirectoryName);

        @Override
        protected File doInBackground(Void... params) {

            Context context = contextWeakReference.get();

            AssetManager assetManager = context.getAssets();

            File file = new File(fileRoot, fileName);

            InputStream in = null;
            OutputStream out = null;
            try {

                file.mkdirs();

                if (file.exists()) {
                    file.delete();
                }

                file.createNewFile();


                in = assetManager.open(fileName);
                Log.d(TAG, "In");

                out = new FileOutputStream(file);
                Log.d(TAG, "Out");

                Log.d(TAG, "Copy file");
                copyFile(in, out);

                Log.d(TAG, "Close");
                in.close();

                out.flush();
                out.close();

                return file;
            } catch (Exception e)
            {
                Log.e(TAG, e.getMessage());
            }

            return null;
        }

        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);
            }
        }

        @Override
        protected void onPostExecute(File file) {
            super.onPostExecute(file);

            Context context = contextWeakReference.get();


            Intent intent = new Intent(Intent.ACTION_VIEW);
            intent.setDataAndType(
                    Uri.fromFile(file),
                    "application/pdf");

            context.startActivity(intent);

        }
    }
}

add this permission in Manifest.xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />