Android 7牛轧糖上的DatePickerDialog全息造型失败

Question

根据我们的客户需求，我们希望在所有Android操作系统版本的DatePickerDialog上保持全息样式，比如：Android 7上的DatePicker-

但在Android 7上似乎不能正常工作：

Android 7上的DatePicker

new DatePickerDialog(getContext(), AlertDialog.THEME_HOLO_LIGHT,
                        mCalendarPickerListener,
                        calendar.get(Calendar.YEAR),
                        calendar.get(Calendar.MONTH),
                        calendar.get(Calendar.DAY_OF_MONTH));

Answer 1

我使用DatePickerDialog提示用户生日。不幸的是，当我尝试时，我收到了许多用户对材料主题对话框的投诉，所以切换到它对我来说不是一个选择：我必须坚持全息主题对话框。

事实证明，Android7.0附带了一个bug：试图在这个平台上使用Holo主题，却回到了为DatePickerDialog使用一个破碎的材料主题。请参见以下两个bug报告：

• 第222808期
• 第222208期

我使用了Jeff Lockhart在这些bug报告中引用的改进形式：

private static final class FixedHoloDatePickerDialog extends DatePickerDialog {
    private FixedHoloDatePickerDialog(Context context, OnDateSetListener callBack,
                                      int year, int monthOfYear, int dayOfMonth) {
        super(context, callBack, year, monthOfYear, dayOfMonth);

        // Force spinners on Android 7.0 only (SDK 24).
        // Note: I'm using a naked SDK value of 24 here, because I'm
        // targeting SDK 23, and Build.VERSION_CODES.N is not available yet.
        // But if you target SDK >= 24, you should have it.
        if (Build.VERSION.SDK_INT == 24) {
            try {
                final Field field = this.findField(
                        DatePickerDialog.class,
                        DatePicker.class,
                        "mDatePicker"
                );

                final DatePicker datePicker = (DatePicker) field.get(this);
                final Class<?> delegateClass = Class.forName(
                        "android.widget.DatePicker$DatePickerDelegate"
                );
                final Field delegateField = this.findField(
                        DatePicker.class,
                        delegateClass,
                        "mDelegate"
                );

                final Object delegate = delegateField.get(datePicker);
                final Class<?> spinnerDelegateClass = Class.forName(
                        "android.widget.DatePickerSpinnerDelegate"
                );

                if (delegate.getClass() != spinnerDelegateClass) {
                    delegateField.set(datePicker, null);
                    datePicker.removeAllViews();

                    final Constructor spinnerDelegateConstructor =
                            spinnerDelegateClass.getDeclaredConstructor(
                                    DatePicker.class,
                                    Context.class,
                                    AttributeSet.class,
                                    int.class,
                                    int.class
                            );
                    spinnerDelegateConstructor.setAccessible(true);

                    final Object spinnerDelegate = spinnerDelegateConstructor.newInstance(
                            datePicker,
                            context,
                            null,
                            android.R.attr.datePickerStyle,
                            0
                    );
                    delegateField.set(datePicker, spinnerDelegate);

                    datePicker.init(year, monthOfYear, dayOfMonth, this);
                    datePicker.setCalendarViewShown(false);
                    datePicker.setSpinnersShown(true);
                }
            } catch (Exception e) { /* Do nothing */ }
        }
    }

    /**
     * Find Field with expectedName in objectClass. If not found, find first occurrence of
     * target fieldClass in objectClass.
     */
    private Field findField(Class objectClass, Class fieldClass, String expectedName) {
        try {
            final Field field = objectClass.getDeclaredField(expectedName);
            field.setAccessible(true);
            return field;
        } catch (NoSuchFieldException e) { /* Ignore */ }

        // Search for it if it wasn't found under the expectedName.
        for (final Field field : objectClass.getDeclaredFields()) {
            if (field.getType() == fieldClass) {
                field.setAccessible(true);
                return field;
            }
        }

        return null;
    }
}

它所做的是：

• 获取属于此对话框的私有datepicker mdatepicker字段
• 获取属于此对话框的私有DatePickerDelegate MDelegate字段
• 检查委托是否已经是DatePickerSpinnerDelegate的实例（我们需要的委托类型）
• 从DatePicker中删除所有视图，因为它们是材料日历小部件
• 创建datepickerspinnerdelegate的新实例，并将其分配给此对话框的mdatepicker的mdelegate字段
• 使用日历信息和一些参数重新初始化MDatePicker，以使其膨胀旋转器

final Context themedContext = new ContextThemeWrapper(
        this.getContext(),
        android.R.style.Theme_Holo_Light_Dialog
);

final DatePickerDialog dialog = new FixedHoloDatePickerDialog(
        themedContext,
        datePickerListener,
        calender.get(Calendar.YEAR),
        calendar.get(Calendar.MONTH),
        calendar.get(Calendar.DAY_OF_MONTH)
);

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