### Question:
DatePicker extends Picker { public void updateDate(int year, int month, int dayOfMonth, boolean animation) { if (!isNewDate(year, month, dayOfMonth)) { return; } setDate(year, month, dayOfMonth); updateSpinners(animation); } DatePicker(Context context, AttributeSet attrs);  DatePicker(Context context, AttributeSet attrs, int defStyleAttr); void setDatePickerFormat(String datePickerFormat); String getDatePickerFormat(); @Override final void onColumnValueChanged(int column, int newVal); void setMinDate(long minDate); long getMinDate(); void setMaxDate(long maxDate); long getMaxDate(); long getDate(); void updateDate(int year, int month, int dayOfMonth, boolean animation);  }### Answer:
@Test public void testInvisibleColumnsAlpha() throws Throwable { Intent intent = new Intent(); intent.putExtra(DatePickerActivity.EXTRA_LAYOUT_RESOURCE_ID, R.layout.datepicker_with_other_widgets); initActivity(intent); mActivityTestRule.runOnUiThread(new Runnable() { @Override public void run() { mDatePickerView.updateDate(2017, 2, 21, false); } }); Thread.sleep(TRANSITION_LENGTH); mActivityTestRule.runOnUiThread(new Runnable() { @Override public void run() { mDatePickerView.updateDate(2017, 2, 20, false); } }); Thread.sleep(TRANSITION_LENGTH); sendKeys(KeyEvent.KEYCODE_DPAD_DOWN); Thread.sleep(TRANSITION_LENGTH); sendKeys(KeyEvent.KEYCODE_DPAD_CENTER); Thread.sleep(TRANSITION_LENGTH); int activeColumn = 0; for (int i = 0; i < 3; i++) { ViewGroup gridView = (ViewGroup) mDatePickerInnerView.getChildAt(2 * i); int childCount = gridView.getChildCount(); int alpha1RowsCount = 0; int alphaNonZeroRowsCount = 0; for (int j = 0; j < childCount; j++) { View pickerItem = gridView.getChildAt(j); if (pickerItem.getAlpha() > 0) { alphaNonZeroRowsCount++; } if (pickerItem.getAlpha() == 1) { alpha1RowsCount++; } } if (i == activeColumn) { assertThat("The active column " + i + " should have only one row with an alpha of " + "1", alpha1RowsCount, is(1)); assertTrue("The active column " + i + " should have more than one view with alpha " + "greater than 1", alphaNonZeroRowsCount > 1); } else { assertThat("The inactive column " + i + " should have only one row with an alpha of" + " 1", alpha1RowsCount, is(1)); assertThat("The inactive column " + i + " should have only one row with a non-zero" + " alpha", alphaNonZeroRowsCount, is(1)); } } }