Android Studio：尝试在空对象引用上调用虚拟方法“void android.view.View.setOnClickListener”
Posted
技术标签:
【中文标题】Android Studio：尝试在空对象引用上调用虚拟方法“void android.view.View.setOnClickListener”【英文标题】：Android Studio: Attempt to invoke virtual method 'void android.view.View.setOnClickListener' on a null object reference 【发布时间】：2019-07-24 09:22:20 【问题描述】：我不断收到 NullPointerException。
Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
我知道这是因为 (SurfaceView)view.findViewById(R.id.surfaceview_show_rectangle) 为空，但我不明白为什么会这样以及如何解决。
我试过这个solution。但它没有用。 下面是我的 Fragment.java 和 xml 文件。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
View view = inflater.inflate(R.layout.fragment_camera2_basic, container, false);
surfaceview = (SurfaceView)view.findViewById(R.id.surfaceview_show_rectangle);
return view;
@Override
public void onViewCreated(final View view, Bundle savedInstanceState)
view.findViewById(R.id.picture).setOnClickListener(this);
view.findViewById(R.id.info).setOnClickListener(this);
mTextureView = (AutoFitTextureView) view.findViewById(R.id.texture);
//view.findViewById(R.id.surfaceview_show_rectangle).setOnClickListener(this);
//surfaceview = (SurfaceView)view.findViewById(R.id.surfaceview_show_rectangle);
surfaceview.setZOrderOnTop(true);
surfaceview.getHolder().setFormat(PixelFormat.TRANSPARENT);
surfaceHolder = surfaceview.getHolder();
surfaceview_result = (SurfaceView)view.findViewById(R.id.surfaceview_show_result);
surfaceview_result.setZOrderOnTop(true);
surfaceview_result.getHolder().setFormat(PixelFormat.TRANSPARENT);
surfaceResultHolder = surfaceview_result.getHolder();
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_
android:layout_>
<SurfaceView
android:id="@+id/surfaceview_show_rectangle"
android:layout_
android:layout_
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp"
/>
<SurfaceView
android:id="@+id/surfaceview_show_result"
android:layout_
android:layout_
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp" />
<com.example.android.camera2basic.AutoFitTextureView
android:id="@+id/texture"
android:layout_
android:layout_
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp" />
<FrameLayout
android:id="@+id/control"
android:layout_
android:layout_
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:background="@color/control_background">
<Button
android:id="@+id/picture"
android:layout_
android:layout_
android:layout_gravity="center"
android:visibility="invisible"
android:text="@string/picture" />
<ImageButton
android:id="@+id/info"
android:contentDescription="@string/description_info"
style="@android:style/Widget.Material.Light.Button.Borderless"
android:layout_
android:layout_
android:layout_gravity="center_vertical|right"
android:padding="20dp"
android:visibility="invisible"
android:src="@drawable/ic_action_info" />
</FrameLayout>
<TextView
android:id="@+id/textView"
android:layout_
android:layout_
android:layout_alignParentStart="true"
android:layout_alignParentBottom="true"
android:layout_marginStart="69dp"
android:layout_marginBottom="37dp"
android:text="Camera2Dome"
android:textColor="#fff"
android:textSize="35sp" />
</RelativeLayout>
以下是我的错误消息。
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.camera2basic, PID: 9168
java.lang.RuntimeException: Unable to start activity ComponentInfocom.example.android.camera2basic/com.example.android.camera2basic.CameraActivity: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.SurfaceView.setZOrderOnTop(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2429)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2493)
at android.app.ActivityThread.access$1000(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1357)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5444)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:746)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.SurfaceView.setZOrderOnTop(boolean)' on a null object reference
at com.example.android.camera2basic.Camera2BasicFragment.onViewCreated(Camera2BasicFragment.java:565)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1430)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1750)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1819)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2590)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2377)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2332)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2239)
at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3231)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3181)
at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:192)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:572)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:177)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1237)
at android.app.Activity.performStart(Activity.java:6317)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2392)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2493)
at android.app.ActivityThread.access$1000(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1357)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5444)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:746)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
I/Process: Sending signal. PID: 9168 SIG: 9
Application terminated.
我非常感谢任何帮助。提前致谢！！
【问题讨论】：
见***.com/a/38718205/192373。 我想你把这个表面视图布局放在一些片段中。我们也需要检查一下。所以发布更多代码。这样它会降低获取解决方案的复杂性 嗨@SIVAKUMAR.J！我更新了上面的xml文件。你能指定你需要哪部分代码吗？ 【参考方案1】：试试这个：
View view = inflater.inflate(R.layout.fragment_camera2_basic, null);
或
LayoutInflater lf = getActivity().getLayoutInflater();
View view = lf.inflate(R.layout.fragment_camera2_basic, container, false);
【讨论】：
【参考方案2】：输入你的代码
surfaceview = (SurfaceView)view.findViewById(R.id.surfaceview_show_rectangle);
在线上方
surfaceview.setZOrderOnTop(true);
那就试试
【讨论】：
【参考方案3】：您正在设置侦听器：
view.findViewById(R.id.picture).setOnClickListener(this);，但是您的活动是否实现了OnClickListener？
【讨论】：
以上是关于Android Studio：尝试在空对象引用上调用虚拟方法“void android.view.View.setOnClickListener”的主要内容，如果未能解决你的问题，请参考以下文章
尝试在空对象引用上调用虚拟方法 'android.graphics.Rect android.graphics.drawable.Drawable.getBounds()'
尝试在空对象引用上调用虚拟方法 'android.view.Window$Callback android.view.Window.getCallback()'
尝试在空对象引用上调用虚拟方法 'android.os.Handler android.support.v4.app.FragmentHostCallback.getHandler()'