Question

所以我正在使用片段并尝试连接点击侦听器。

public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View contentView = inflater.inflate(R.layout.layout1, null);
      //  View contentView=super.onCreateView(inflater,null,savedInstanceState,R.layout.layout1);
        startButton= (Button) getView().findViewById(R.id.button);

这是按钮的XML

 <Button
            android:layout_width="100dp"
            android:layout_height="wrap_content"
            android:text="Start Time"
            android:id="@+id/button"
            android:layout_alignParentLeft="true"
            android:layout_marginLeft="28dp"
            android:layout_marginTop="10dp"
            android:background="#1e497c"
            android:textColor="#ffffff"/>

这是我的例外

02-28 16：49：57.162 14375-14375 / com.example.listviewandroid E / AndroidRuntime：FATAL

EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.listviewandroid/com.example.listviewandroid.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
            at android.app.ActivityThread.access$700(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:175)
            at android.app.ActivityThread.main(ActivityThread.java:5279)
            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:1102)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.example.fragment.Fragment1.onCreateView(Fragment1.java:43)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
            at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:556)
            at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1181)
            at android.app.Activity.performStart(Activity.java:5293)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2218)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
            at android.app.ActivityThread.access$700(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:175)
            at android.app.ActivityThread.main(ActivityThread.java:5279)
            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:1102)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
            at dalvik.system.NativeStart.main(Native Method)

显而易见它无法找到按钮或正在发生的事情，我无法弄清楚。非常感谢任何帮助。

Answer 1

只需在onCreateView

中使用此功能即可

    View contentView = inflater.inflate(R.layout.layout1, container, false);
    startButton= (Button) contentView.findViewById(R.id.button);
    return contentView;

Answer 2

在getView()返回之前，您无法使用onCreateView()，因为它是负责创建所述视图的方法。您应该将代码更改为

public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View contentView = inflater.inflate(R.layout.layout1, null);
        startButton = (Button) contentView.findViewById(R.id.button);

或者，覆盖onViewCreated()并在该方法中实施按钮设置（使用getView()。

Answer 3

这条线毫无意义：

startButton= (Button) getView().findViewById(R.id.button);

你还没有View，你还在创建它..

您可以这样做：

 startButton= (Button)contentView.findViewById(R.id.button);

或等到onCreateView方法返回刚刚创建的实际视图，然后在onCreateView返回视图后，您将能够使用“getView”方法获取视图的引用。

希望它有帮助！

问候！

fragment.onCreateView导致空指针异常

3 个答案: