android非平凡findViewById NullPointerException

我有日历库，其中有CalendarViewActivity。
我的项目使用此库并扩展CalendarViewActivity以设置自定义活动标题。
日历活动：

public class CalendarActivity extends CalendarViewActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // set custom activity title
        getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE,
                R.layout.window_title);
        TextView title = (TextView) getWindow().findViewById(R.id.txt_header);
        if (isGo) {
            title.setText(getResources().getString(R.string.title_date_go));
        } else {
            title.setText(getResources().getString(R.string.title_date_go_back));
        }
    }

}

在一些设备中（确切地说是：华硕tf101、三星Galaxy Gio S5660），我在这一行中得到了NullPointerException：

super.onCreate(savedInstanceState);  

此引用库中的此行（此处显示异常）：

Xml布局（库中的CalendarViewActivity）：

---

我在清单中移动了屏幕方向的定义，这解决了我的问题。

问题可能与getWindow（）或其他与窗口相关的方法有关，因为它因设备而异。请参阅，如果发布堆栈跟踪，则在getWindow（）之前会出现异常，也许有人可以告诉您出了什么问题。是的，但可能正是因为这样，not savebundledinstance才不会抛出错误。该CalendarViewActivity是否有多个xml布局文件？与该设备对应的xml布局（取决于配置）可能没有按钮，或者没有提供id参数？

((Button) findViewById(R.id.btn_today)).setOnClickListener(this);

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/background"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/calendar_header"
        android:gravity="center_vertical"
        android:orientation="horizontal">

        <ImageView
            android:id="@+id/prevMonth"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:contentDescription="@string/descr_btn_prev_month"
            android:src="@drawable/calendar_left_arrow_selector" >
        </ImageView>

        <TextView
            android:id="@+id/currentMonth"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.6"
            android:gravity="center"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:textColor="@android:color/black" >
        </TextView>

        <ImageView
            android:id="@+id/nextMonth"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:contentDescription="@string/descr_btn_next_month"
            android:src="@drawable/calendar_right_arrow_selector" >
        </ImageView>
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_marginLeft="15dp"
        android:layout_marginRight="15dp" >

        <GridView
            android:id="@+id/calendarHeader"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:listSelector="@android:color/transparent"
            android:numColumns="7" >
        </GridView>

        <GridView
            android:id="@+id/calendar"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/calendar_bg"
            android:listSelector="@android:color/transparent"
            android:numColumns="7">
        </GridView>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:layout_marginTop="15dp">
            <Button
                android:id="@+id/btn_today"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:background="@drawable/calendar_button"
                android:text="@string/btn_today"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:layout_marginRight="5dp"
                android:textAppearance="?android:attr/textAppearanceMedium"/>
            <Button
                android:id="@+id/btn_tomorrow"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:background="@drawable/calendar_button"
                android:text="@string/btn_tomorrow"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:layout_marginLeft="5dp"
                android:textAppearance="?android:attr/textAppearanceMedium"/>
        </LinearLayout>
    </LinearLayout>

</LinearLayout>

java.lang.RuntimeException: Unable to start activity ComponentInfo{net.package.package/net.package.package.ui.activities.CalendarActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
        at android.app.ActivityThread.access$1500(ActivityThread.java:117)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:130)
        at android.app.ActivityThread.main(ActivityThread.java:3687)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:507)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
        at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
        at com.metalex.calendarview.UI.Activities.CalendarViewActivity.onCreate(CalendarViewActivity.java:118)
        at net.aviascanner.aviascanner.ui.activities.CalendarActivity.onCreate(CalendarActivity.java:20)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
        ... 11 more
java.lang.NullPointerException
        at com.metalex.calendarview.UI.Activities.CalendarViewActivity.onCreate(CalendarViewActivity.java:118)
        at net.aviascanner.aviascanner.ui.activities.CalendarActivity.onCreate(CalendarActivity.java:20)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
        at android.app.ActivityThread.access$1500(ActivityThread.java:117)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:130)
        at android.app.ActivityThread.main(ActivityThread.java:3687)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:507)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
        at dalvik.system.NativeStart.main(Native Method)