NullPointerException与使用ButterKnife

Question

我启用了像这这样的注释处理，并遵循以下代码：

public class MainFragment extends Fragment implements WeatherUpdater.AsyncResponse {

@BindView(R.id.temperature_max) TextView temperature_max;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_main, container, false);
    ButterKnife.bind(this, view);
    temperature_max.setText("NULL POINTER!");
...
return view;
}
}

我的结构很复杂：

<?xml version="1.0" encoding="utf-8"?>
<ScrollView>

<RelativeLayout>

    <LinearLayout>
    </LinearLayout>

    <LinearLayout>

        <RelativeLayout>

            <RelativeLayout>

                <TextView>

                <TextView
                    android:id="@+id/temperature_max"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentRight="true"
                    android:textSize="20sp" />
            </RelativeLayout>

            ...
</ScrollView>

这个逻辑猫：

E/AndroidRuntime: FATAL EXCEPTION: main
                                               Process: com.my.app, PID: 22813
                                               java.lang.RuntimeException: Unable to start activity ComponentInfo{com.my.app/com.my.app.ui.activity.MainActivity}: java.lang.NullPointerException
                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2224)
                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2283)
                                                   at android.app.ActivityThread.access$800(ActivityThread.java:144)
                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
                                                   at android.os.Handler.dispatchMessage(Handler.java:102)
                                                   at android.os.Looper.loop(Looper.java:136)
                                                   at android.app.ActivityThread.main(ActivityThread.java:5158)
                                                   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:732)
                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
                                                   at dalvik.system.NativeStart.main(Native Method)
                                                Caused by: java.lang.NullPointerException
                                                   at com.my.app.ui.fragment.MainFragment.onCreateView(MainFragment.java:28)
                                                   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:685)
                                                   at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
                                                   at android.app.Activity.performStart(Activity.java:5319)
                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2190)
                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2283) 
                                                   at android.app.ActivityThread.access$800(ActivityThread.java:144) 
                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205) 
                                                   at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                   at android.os.Looper.loop(Looper.java:136) 
                                                   at android.app.ActivityThread.main(ActivityThread.java:5158) 
                                                   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:732) 
                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566) 
                                                   at dalvik.system.NativeStart.main(Native Method) 

哦，是的，我用的是->‘com.jakewharton:蝴蝶刀:8.0.1’这个梯度版本。

但我不知道为什么会出现NullPointerException。我在网上搜索一个问题，但没有找到解决办法。有人帮我吗？谢谢。

Answer 1

我想您忘了返回您的View。

public class MainFragment extends Fragment implements WeatherUpdater.AsyncResponse {

@BindView(R.id.temperature_max) TextView temperature_max;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_main, container, false);
    ButterKnife.bind(this, view);
    temperature_max.setText("NULL POINTER!");
    return view; // This need to be return.
}
}

编辑1 :

@Bind取代了@InjectView和@InjectViews。ButterKnife.bind和ButterKnife.unbind分别取代ButterKnife.inject和ButterKnife.reset。

并添加以下内容：.

TextView temperature_max = ButterKnife.findById(view, R.id.temperature_max);

看看这个参考这里。

Answer 2

您应该使用@Bind而不是@BindView。其他一切都很好。