Question

我有一个使用导航抽屉的Android应用程序。我想在其中一个片段中对线性布局上的onClick事件做出响应，通过单击导航抽屉中的项目进行访问。

这是片段代码 - HomeFragment.java

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    if (container == null) { return null; }
    View rootView = inflater.inflate(R.layout.fragment_home, container, false);

    try {
        take_photo = (LinearLayout) getView().findViewById(R.id.btn_take_photo);
        open_gallery = (LinearLayout) getView().findViewById(R.id.btn_open_gallery);
    } catch (NullPointerException npe) {
        Log.e("samako", npe.toString(), npe);
    }
    return rootView;
}

这是线性布局

<LinearLayout
        android:id="@+id/btn_take_photo"
        android:layout_width="match_parent"
        android:layout_height="55dp"
        android:padding="5dp"
        android:orientation="horizontal"
        android:weightSum="10"
        android:descendantFocusability="blocksDescendants"
        android:clickable="true"
        android:background="@drawable/presc_bg"
        android:layout_margin="10dp">



        <ImageView
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_margin="5dp"
            android:layout_height="match_parent"
            android:layout_gravity="center"
            android:background="@drawable/btn_camera" />

        <TextView
            android:layout_width="0dp"
            android:layout_weight="9"
            android:gravity="center"
            android:textColor="@color/white"
            android:text="Take a picture of your prescription"
            android:layout_height="match_parent" />

    </LinearLayout>

但是一旦安装应用程序并运行，我就会收到错误并且应用程序崩溃，至少，直到我添加了try catch。这是我得到的错误：

02-28 15:25:38.598  22386-22386/com.genesis.genapp E/samako﹕ java.lang.NullPointerException
java.lang.NullPointerException
        at com.genesis.genapp.fragments.HomeFragment.onCreateView(HomeFragment.java:31)
        at android.app.Fragment.performCreateView(Fragment.java:1700)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
        at android.app.BackStackRecord.run(BackStackRecord.java:684)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
        at android.app.Activity.performStart(Activity.java:5240)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

试试这个..

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_home, container, false);
        take_photo = (LinearLayout) rootView.findViewById(R.id.btn_take_photo);
        open_gallery = (LinearLayout)rootView.findViewById(R.id.btn_open_gallery);
    return rootView;
}

Answer 2

更改为

 take_photo = (LinearLayout) rootView.findViewById(R.id.btn_take_photo);
 open_gallery = (LinearLayout) rootView.findViewById(R.id.btn_open_gallery);

或onActivityCreated

 take_photo = (LinearLayout) getView().findViewById(R.id.btn_take_photo);
 open_gallery = (LinearLayout) getView().findViewById(R.id.btn_open_gallery);

getView返回null。打电话太早了。在onActivityCreated。

中使用它

访问linearlayout时片段代码中的nullpointerexception

2 个答案: