NullPointerException - FrameLayout

Question

在加载片段活动时，意外地收到了一个空指针异常错误。我指的是FrameLayout将用户引导到另一个活动(按一下按钮)。

11-10 07:31:58.773: E/AndroidRuntime(10340): FATAL EXCEPTION: main
    11-10 07:31:58.773: E/AndroidRuntime(10340): java.lang.NullPointerException
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at com.dooba.beta.ThirdFragment.onCreateView(ThirdFragment.java:22)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.os.Handler.handleCallback(Handler.java:615)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.os.Handler.dispatchMessage(Handler.java:92)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.os.Looper.loop(Looper.java:137)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at android.app.ActivityThread.main(ActivityThread.java:4745)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at java.lang.reflect.Method.invokeNative(Native Method)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at java.lang.reflect.Method.invoke(Method.java:511)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    11-10 07:31:58.773: E/AndroidRuntime(10340):    at dalvik.system.NativeStart.main(Native Method)

以下是活动代码：

public class ThirdFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.activity_city, container, false);

        FrameLayout icity = (FrameLayout)getView().findViewById(R.id.flCityBac);
        icity.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                getActivity().startActivity(new Intent(getActivity(), MainActivity.class));
            }
        });

        return rootView;


    }


}

下面是布局代码：

<RelativeLayout 
    android:id="@+id/layout_gridview_item"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:alpha="1"
    android:gravity="top"
    android:background="#DEDEDE" >

        <RelativeLayout
          android:id="@+id/background"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:background="@drawable/background_with_shadow"
          android:layout_centerHorizontal="true"
          android:layout_marginTop="20dp"
                    android:layout_below="@+id/ttitle"

          android:padding="5dp"
         android:alpha="0.9"
          android:orientation="vertical"
          >



       <FrameLayout
            android:id="@+id/flCityBac"
        android:layout_width="wrap_content"
        android:layout_height="175dp"
        android:layout_gravity="center_horizontal"
        android:layout_weight="30" >

      <ImageView
          android:id="@+id/img_cityBac"
          android:layout_width="300dp"
          android:layout_height="175dp"
          android:alpha="1"
          android:background="@drawable/vancouvero2"
          android:contentDescription="@null"
          android:paddingLeft="0dp"
          android:paddingRight="4dp"
           />

      <TextView
              android:id="@+id/text_Title"
              android:layout_width="300dp"
              android:layout_height="40dp"

              android:layout_gravity="bottom"

              android:padding="0dp"

              android:ellipsize="marquee"
              android:gravity="center"
                                           android:background="#E41B17"
              android:alpha="0.85"
              android:maxLines="1"
              android:text="Vancouver, Canada"
              android:textAllCaps="true"
              android:textColor="#ffffff"
              android:textSize="18sp"
              android:textStyle="bold"
              android:typeface="serif" />



              </FrameLayout>

       </RelativeLayout>

        <TextView
            android:id="@+id/ttitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="32dp"
            android:alpha="0.85"
            android:ellipsize="marquee"
            android:gravity="center"
            android:maxLines="1"
            android:text="Discover"
            android:textAllCaps="true"
            android:textColor="#E41B17"
            android:textSize="28sp"
            android:textStyle="bold"
            android:typeface="serif" />

</RelativeLayout>

Answer 1

而不是

getView().findViewById(R.id.flCityBac);

使用：

rootView.findViewById(R.id.flCityBac);

您不能使用getView，因为您的视图尚未创建。

希望它对你有帮助！

Answer 2

public class ThirdFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.activity_city, container, false);

        FrameLayout icity = (FrameLayout)rootView.findViewById(R.id.flCityBac);//Use rootView here.
        icity.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                getActivity().startActivity(new Intent(getActivity(), MainActivity.class));
            }
        });

        return rootView;


    }


}