在DatePickerDialog中使用DatePicker setMaxDate（）时发生NullPointerException [英] NullPointerException when using DatePicker setMaxDate() in a DatePickerDialog

问题描述

我正在使用DatePickerDialog，并且试图设置最小和最大日期，以便用户只能选择前24小时或后24小时内的日期。

I am using a DatePickerDialog, and I am trying to set the minimum and maximum dates such that the user can only select a date within the previous 24 hours or next 24 hours.

这是代码。 （请注意，只有在Android 3.0或更高版本上运行时，它才会尝试设置最小/最大范围。）

Here is the code. (Note that it only tries to set the min/max range if running on Android 3.0 or higher.)

private void showDatePickerDialog() {
    DatePickerDialog.OnDateSetListener listener = new DatePickerDialog.OnDateSetListener() {
        @Override
        public void onDateSet(DatePicker view, int year, int monthOfYear,
                              int dayOfMonth) {
            calendar.set(Calendar.YEAR, year);
            calendar.set(Calendar.MONTH, monthOfYear);
            calendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);
            onCalendarChanged();
        }
    };

    DatePickerDialog dialog = new DatePickerDialog(this,
                                                   listener,
                                                   calendar.get(Calendar.YEAR),
                                                   calendar.get(Calendar.MONTH),
                                                   calendar.get(Calendar.DAY_OF_MONTH));
    setDatePickerDialogRange(dialog);
    dialog.show();
}

@SuppressLint("NewApi")
private void setDatePickerDialogRange(DatePickerDialog dialog) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        DatePicker picker = dialog.getDatePicker();
        long oneDayMilliseconds = 24 * 60 * 60 * 1000;
        long nowMilliseconds = new Date().getTime();
        long minDate = nowMilliseconds - oneDayMilliseconds;
        long maxDate = nowMilliseconds + oneDayMilliseconds;
        picker.setMinDate(minDate);
        picker.setMaxDate(maxDate);
    }
}

在2.2设备上运行时效果很好，但是在4.0.4设备（Galaxy Tab 2 7.0）上，出现此异常：

This works fine when running on a 2.2 device, but on a 4.0.4 device (Galaxy Tab 2 7.0), I get this exception:

11-14 07:58:08.917: E/AndroidRuntime(16611): FATAL EXCEPTION: main
11-14 07:58:08.917: E/AndroidRuntime(16611): java.lang.NullPointerException
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.CalendarView.onScroll(CalendarView.java:910)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.CalendarView.access$600(CalendarView.java:74)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.CalendarView$2.onScroll(CalendarView.java:771)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.AbsListView.invokeOnItemScrollListener(AbsListView.java:1391)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.ListView.layoutChildren(ListView.java:1705)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.AbsListView.onLayout(AbsListView.java:2040)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1644)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1502)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1644)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1633)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1417)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1644)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1502)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.View.layout(View.java:11330)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewGroup.layout(ViewGroup.java:4235)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1548)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2505)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.os.Looper.loop(Looper.java:137)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at android.app.ActivityThread.main(ActivityThread.java:4514)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at java.lang.reflect.Method.invokeNative(Native Method)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at java.lang.reflect.Method.invoke(Method.java:511)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
11-14 07:58:08.917: E/AndroidRuntime(16611):    at dalvik.system.NativeStart.main(Native Method)

这立即发生。 DatePickerDialog永远不会显示。

This happens immediately. The DatePickerDialog is never displayed.

如果我注释掉 setMaxDate（）行，则可以正常工作。在这种情况下，将遵守最小日期。

If I comment out the setMaxDate() line, then it works fine. In this case, the minimum date is respected.

如果将其更改为 setMaxDate（nowMilliseconds），我仍然获取NullPointerException。

If I change it to setMaxDate(nowMilliseconds), I still get the NullPointerException.

推荐答案

从事此工作已经有一段时间了。这是Android中的错误。只需关闭日历视图，就可以了：

Been working on this for quite some time. This is a bug in Android. Just turn off the Calendar View and you'll be fine:

picker.setCalendarViewShown(false);

这篇关于在DatePickerDialog中使用DatePicker setMaxDate（）时发生NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！