Android 加载片段时出现NullPointerException

当我尝试加载一个片段时，我得到一个NullPointerException

堆栈跟踪如下所示：

08-07 00:43:11.780: E/AndroidRuntime(1366): FATAL EXCEPTION: main
08-07 00:43:11.780: E/AndroidRuntime(1366): java.lang.RuntimeException: Unable to start activity ComponentInfo{ca.ioto.atractr_v2/ca.ioto.atractr_v2.Atractr}: java.lang.NullPointerException
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.os.Looper.loop(Looper.java:137)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at java.lang.reflect.Method.invokeNative(Native Method)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at java.lang.reflect.Method.invoke(Method.java:511)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at dalvik.system.NativeStart.main(Native Method)
08-07 00:43:11.780: E/AndroidRuntime(1366): Caused by: java.lang.NullPointerException
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.BackStackRecord.run(BackStackRecord.java:661)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.Activity.performStart(Activity.java:5113)
08-07 00:43:11.780: E/AndroidRuntime(1366):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2153)
08-07 00:43:11.780: E/AndroidRuntime(1366):     ... 11 more

我所有的XML都是正常声明的，我开始的活动的XML如下所示

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".Atractr" >

<fragment
    android:id="@+id/fragment1"
    android:name="ca.ioto.atractr_v2.FindNearestDevicesFragment"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    tools:layout="@layout/findnearestdevices_fragment" />

<fragment
    android:id="@+id/fragment2"
    android:name="ca.ioto.atractr_v2.ChatFragment"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/fragment1"
    android:layout_alignTop="@+id/fragment1"
    tools:layout="@layout/chat_fragment" />

</RelativeLayout>

我不知道从哪里得到NullPointerException（或者为什么抛出它）

编辑：请求了更多的代码，因此我添加了更多的代码：

初始化Echord

方法：

private void initializeChord(){
    chordMan = ChordManager.getInstance(this);
    chordMan.setTempDirectory("/storage/emulated/0/Download");
    chordMan.setHandleEventLooper(getMainLooper());
    ArrayList<Integer> interfaces = (ArrayList<Integer>) chordMan.getAvailableInterfaceTypes();
    int result = chordMan.start(interfaces.get(0), chordManListener);
    if (result == ChordManager.ERROR_FAILED) {
        Utils.singleButtonAlert("Error","An error occured when starting Chord", this);
        return;
    }
    chordStarted = true;
}

   private void changeFragment(int changeToFragment)
{
    fragTransaction = getFragmentManager().beginTransaction();
    switch (changeToFragment){

    case FINDNEARESTDEVICES:
        currentFragment = changeToFragment;
        fragTransaction.show(newFragment);
        fragTransaction.hide(chatFragment);
        break;
    case CHAT:
        currentFragment = changeToFragment;
        fragTransaction.show(chatFragment);
        fragTransaction.hide(newFragment);
        break;
    }
    fragTransaction.commit();
}

Atractr类的一些类成员：

private ChordManager chordMan;
private IChordChannel commChannel;
private FindNearestDevicesFragment newFragment;
private ChatFragment chatFragment;
private FragmentTransaction fragTransaction;
private static boolean chordStarted = false;
public final static int FINDNEARESTDEVICES = 1000;
public final static int CHAT = 1001;
private static int currentFragment = FINDNEARESTDEVICES; 

---

函数显示和隐藏现有片段上的工作

隐藏现有片段。这仅与视图已添加到容器中的片段相关

显示以前隐藏的片段。这仅与视图已添加到容器中的片段相关

但片段的生命周期与活动不同，在调用活动的onCreate时，可能尚未创建和附加片段

在调用changeFragment或changeFragment内部时检查null

如果您希望在开始时隐藏其中一个片段，请考虑从OnAdTraceDeD（）方法中的片段中生成回调调用，或者手动添加片段而不是XML。

---

我的首选选项是手动添加片段。

不确定，但您的xml布局出现问题android:layout\u alignLeft=“@+id/fragment1”android:layout\u alignTop=“@+id/fragment1”删除+到android:layout\u alignLeft=“@id/fragment1”android:layout\u alignTop=“@id/fragment1”发布更多代码，我想到了类成员及其默认值和initializeChord（）方法。也许这与：

private ChordManager chordMan;
private IChordChannel commChannel;
private FindNearestDevicesFragment newFragment;
private ChatFragment chatFragment;
private FragmentTransaction fragTransaction;
private static boolean chordStarted = false;
public final static int FINDNEARESTDEVICES = 1000;
public final static int CHAT = 1001;
private static int currentFragment = FINDNEARESTDEVICES;