Android fragments 如何从父FragmentActivity检索包装在另一个片段中的ListFragment

我有一个FragmentActivitya，它包含片段B，它包含ListFragmentC

+---------------+
| A +---------+ |
|   | B +---+ | |
|   |   | C | | |
|   |   +---+ | |
|   +---------+ |
+---------------+

FragmentActivityA的布局是一个简单的ViewPager。FragmentB的布局是一个线性布局，其中包含一个EditText小部件和一个Fragment小部件：

<LinearLayout
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:orientation="vertical"
tools:context=".FinderFragment">

<EditText
    android:id="@+id/editedName"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="search by name"
    android:layout_weight="0" />

<fragment
    android:id="@+id/contactsFragment"
    android:name="frenkapps.yourteam.ContactsFragment"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1" />

</LinearLayout>

我不知道为什么会发生这种情况，因为ContactsFragment类的onCreate（）方法肯定会被调用

它可以帮助记录：

java.lang.RuntimeException: Unable to start activity ComponentInfo{frenkapps.yourteam/frenkapps.yourteam.Main}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at frenkapps.yourteam.Main.onStart(Main.java:42)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1133)
        at android.app.Activity.performStart(Activity.java:4475)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1929)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)

---

是的，但是ListFragment C实现了

LoaderCallback

，它使用

SimpleCorsOrAdapter

显示查询结果。如果我在父级

FragmentActivity

A上移动这些接口，UI会被阻止吗？我解决了我的问题，在C类上实现了创建活动的

方法，在这里我设置了侦听器。。。我是塔德。。
java.lang.RuntimeException: Unable to start activity ComponentInfo{frenkapps.yourteam/frenkapps.yourteam.Main}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at frenkapps.yourteam.Main.onStart(Main.java:42)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1133)
        at android.app.Activity.performStart(Activity.java:4475)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1929)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)