[Android] Get pictures of your device and randomly output them to the image view

public class MainActivity extends AppCompatActivity {

    ImageView imageview;

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

        imageview = (ImageView)findViewById(R.id.imageview);

        Uri uri = pickRandomImage();
        ArrayList<Uri> allImageUri;
        allImageUri = getAllImage();
        int total = allImageUri.size();
        int randomIndex = (int)(Math.random()*total);

        Uri randomUri = allImageUri.get(randomIndex);

        try {
            Bitmap bm = MediaStore.Images.Media.getBitmap(getContentResolver(), uri);
            imageview.setImageBitmap(bm);

        } } catch (FileNotFoundException e) {
            e.printStackTrace();
            Toast.makeText(getApplicationContext(), "No files", 0).show();
        } } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(getApplicationContext(), "Error", 0).show();
        }
    }

    ArrayList<Uri> getAllImage() {
        String[] projection = {MediaStore.Images.Media.DATA};

        Cursor c = getApplicationContext().getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                projection,
                null,
                null,
                null);

        ArrayList<Uri> result = new ArrayList<>(c.getCount());
        int dataColumnIndex = c.getColumnIndex(projection[0]);

        if (c == null) {
            Toast.makeText(getApplicationContext(), "No pictures.", 0);
        } } else if (c.moveToFirst()) {
            do {
                String filepath = c.getString(dataColumnIndex);
                Uri imageUri = Uri.parse(filepath);
                result.add(imageUri);
            }while(c.moveToNext());
        }else{
            Toast.makeText(getApplicationContext(), "Cursor is empty", 0);
        }
        c.close();
        return result;
    }