最近使用了DatePicker 这个控件，采用的是往上又一次分装的这种，就是两个卡片切换选择年月日和时间。
有一个需求时这个选择器不显示出来“天”的这个选项。查资料发现，有人做了实现，具体代码还没弄清楚，可以研究DatePicker源码，这里主要是根据反射原理获取到DatePicker中的一些域，同时代码获取到布局，然后在进行操作，如：修改分割线颜色，隐藏某一个域等。这里做一个记录，方便后续使用。
创建对象是调用方法：
/**
* 隐藏“天”
* @param mDatePicker
*/
private void hideDay(DatePicker mDatePicker) {
try {
/* 处理android5.0以上的特殊情况 */
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
int daySpinnerId = Resources.getSystem().getIdentifier("day", "id", "android");
if (daySpinnerId != 0) {
View daySpinner = mDatePicker.findViewById(daySpinnerId);
if (daySpinner != null) {
daySpinner.setVisibility(View.GONE);
}
}
} else {
Field[] datePickerfFields = mDatePicker.getClass().getDeclaredFields();
for (Field datePickerField : datePickerfFields) {
if ("mDaySpinner".equals(datePickerField.getName()) || ("mDayPicker").equals(datePickerField.getName())) {
datePickerField.setAccessible(true);
Object dayPicker = new Object();
try {
dayPicker = datePickerField.get(mDatePicker);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
}
((View) dayPicker).setVisibility(View.GONE);
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}这个方法就可以完成需求的操作。由此方法也能衍生出“月”，“年”等不同项的操作，这几个操作没有详细了解，待后续研究。
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
int daySpinnerId = Resources.getSystem().getIdentifier("day", "id", "android");
if (daySpinnerId != 0) {
View daySpinner = dp_mes.findViewById(daySpinnerId);
if (daySpinner != null) {
daySpinner.setVisibility(View.GONE);
}
}
int monthSpinnerId = Resources.getSystem().getIdentifier("month", "id", "android");
if (monthSpinnerId != 0) {
View monthSpinner = dp_mes.findViewById(monthSpinnerId);
if (monthSpinner != null) {
monthSpinner.setVisibility(View.VISIBLE);
}
}
int yearSpinnerId = Resources.getSystem().getIdentifier("year", "id", "android");
if (yearSpinnerId != 0) {
View yearSpinner = dp_mes.findViewById(yearSpinnerId);
if (yearSpinner != null) {
yearSpinner.setVisibility(View.GONE);
}
}
} else { //Older SDK versions
Field f[] = dp_mes.getClass().getDeclaredFields();
for (Field field : f) {
if (field.getName().equals("mDayPicker") || field.getName().equals("mDaySpinner")) {
field.setAccessible(true);
Object dayPicker = null;
try {
dayPicker = field.get(dp_mes);
} catch (IllegalAccessException e) {
e.printStackTrace();
}
((View) dayPicker).setVisibility(View.GONE);
}
if (field.getName().equals("mMonthPicker") || field.getName().equals("mMonthSpinner")) {
field.setAccessible(true);
Object monthPicker = null;
try {
monthPicker = field.get(dp_mes);
} catch (IllegalAccessException e) {
e.printStackTrace();
}
((View) monthPicker).setVisibility(View.VISIBLE);
}
if (field.getName().equals("mYearPicker") || field.getName().equals("mYearSpinner")) {
field.setAccessible(true);
Object yearPicker = null;
try {
yearPicker = field.get(dp_mes);
} catch (IllegalAccessException e) {
e.printStackTrace();
}
((View) yearPicker).setVisibility(View.GONE);
}
}
}
}