如何解决为 MaterialDatePicker 扩展 DialogFragment
我想从 DatePickerDialog 迁移到 MaterialDatePicker。 我在从 MaterialDatePicker 调用 getDialog 时遇到问题,对话框结果始终为空。
这是一个错误,还是 MaterialDatePicker 不支持该功能?
DatePickerDialog
private static class BirthDateUpdater extends DialogFragment implements DatePickerDialog.OnDateSetListener {
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// create calendar instance
final Calendar c = Calendar.getInstance();
// set calendar to birthdate
c.setTimeInMillis(getBirthDate().getTime());
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int day = c.get(Calendar.DAY_OF_MONTH);
// Create a new instance of DatePickerDialog and return it
return new DatePickerDialog(getActivity(),this,year,month,day);
}
public void onDateSet(DatePicker view,int year,int month,int day) {
// process date selected in here
}
}
MaterialDatePicker 这里的问题 - picker.getDialog() 的结果总是为空?
public static class BirthDateUpdater extends DialogFragment implements
MaterialPickerOnPositiveButtonClickListener<Long>,DialogInterface.OnCancelListener {
private Dialog dialog;
public BirthDateUpdater() {
}
@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
try {
// builder
MaterialDatePicker.Builder<Long> builder = MaterialDatePicker.Builder.datePicker();
builder.setTitleText("Select Date");
// set date to BirthDate
builder.setSelection(getBirthDate().getTime());
// picker
MaterialDatePicker<Long> picker = builder.build();
// add event
picker.addOnPositiveButtonClickListener(this);
picker.addOnCancelListener(this);
// dialog
dialog = picker.getDialog(); // error in here (dialog is null)?
} catch (Exception ex) {
ex.printstacktrace();
}
return dialog;
}
@Override
public void onPositiveButtonClick(Long selection) {
try {
Calendar dateSelected = Calendar.getInstance();
dateSelected.setTimeInMillis(selection);
// process date selected in here
} catch (Exception ex) {
ex.printstacktrace();
}
}
@Override
public void onCancel(@NonNull DialogInterface dialog) {
dialog.dismiss();
}
}
解决方法
MaterialDatePicker
已经是 DialogFragment。在你的情况下 picker.getDialog()
返回 null 因为在引擎盖下 DialogFragment 写入值到 DialogFragment.mDialog(value of this field returns picker.getDialog()
) 从生命周期回调 onCreateDialog() 提交,它将在调用后被称为异步对话框的 show 方法,即当您调用 picker.show(fragmentManager) 然后在选择器的 onCreateDialog 中,您将可以从 getDialog()
方法中获得非空值。
在你的情况下,你不应该扩展 DialogFragment 或 MaterialDatePicker(它是 final ),而你可以创建像 birthDateUpdater
这样的方法:
public DialogFragment birthDateUpdater() {
MaterialDatePicker.Builder<Long> builder = MaterialDatePicker.Builder.datePicker();
builder.setTitleText("Select Date");
// set date to BirthDate
builder.setSelection(getBirthDate().getTime());
// picker
MaterialDatePicker<Long> picker = builder.build();
// add event
picker.addOnPositiveButtonClickListener(selection -> {
try {
Calendar dateSelected = Calendar.getInstance();
dateSelected.setTimeInMillis(selection);
// process date selected in here
} catch (Exception ex) {
ex.printStackTrace();
}
});
picker.addOnCancelListener(dialog -> {
dialog.dismiss();
});
return picker
}
或者创建类,工厂,任何将封装此逻辑的东西。
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