AndroidUtils.java

@SuppressWarnings("WeakerAccess")
public class AndroidUtils {

    public static int getColorFromAttr(Context ctx, int attributeId) {
        int colorId = getResourceIdFromAttr(ctx, attributeId);
        return ContextCompat.getColor(ctx, colorId);
    }

    public static int dpToPx(int dp, Context ctx) {
        DisplayMetrics displayMetrics = ctx.getResources().getDisplayMetrics();
        return Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT));
    }

    public static Drawable getDrawableFromAttr(Context ctx, int attributeId) {
        int drawableId = getResourceIdFromAttr(ctx, attributeId);
        return ContextCompat.getDrawable(ctx, drawableId);
    }

    public static int getResourceIdFromAttr(Context ctx, int attributeId) {
        TypedValue typedValue = new TypedValue();
        Resources.Theme theme = ctx.getTheme();
        theme.resolveAttribute(attributeId, typedValue, true);
        return typedValue.resourceId;
    }

    public static void hideKeyboard(Activity activity) {
        View view = activity.getCurrentFocus();
        if (view != null) {
            InputMethodManager imm = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
            if (imm != null) {
                imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
            }
        }
    }

    public static void showDateTimePickerDialog(Context ctx, Date startDate, DateReadyListener listener) {
        showDatePickerDialog(ctx, startDate, date -> showTimePickerDialog(ctx, date, listener));
    }

    public static void showDatePickerDialog(Context ctx, Date startDate, DateReadyListener listener) {
        Calendar calendar = Calendar.getInstance();
        Date now = calendar.getTime();
        if (startDate == null) {
            startDate = now;
        }
        calendar.setTime(startDate);

        DatePickerDialog.OnDateSetListener dateSetListener = (datePicker, year, monthOfYear, dayOfMonth) -> {
            calendar.set(year, monthOfYear, dayOfMonth);
            listener.onDateReady(calendar.getTime());
        };

        DatePickerDialog dialog = new DatePickerDialog(ctx,
                dateSetListener,
                calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH));

        dialog.getDatePicker().setMaxDate(now.getTime());
        dialog.show();
    }

    public static void showTimePickerDialog(Context ctx, Date startDate, DateReadyListener listener) {
        Calendar calendar = Calendar.getInstance();
        Date now = calendar.getTime();
        if (startDate == null) {
            startDate = now;
        }
        calendar.setTime(startDate);

        TimePickerDialog.OnTimeSetListener timeSetListener = (timePicker, hour, minute) -> {
            calendar.set(Calendar.HOUR, hour);
            calendar.set(Calendar.MINUTE, minute);
            listener.onDateReady(calendar.getTime());
        };

        TimePickerDialog dialog = new TimePickerDialog(ctx,
                timeSetListener,
                calendar.get(Calendar.HOUR),
                calendar.get(Calendar.MINUTE),
                true);

        dialog.show();
    }

    public interface DateReadyListener {
        void onDateReady(Date date);
    }
}