Question

我正在运行以下代码，它在行iv4.setVisibility（View.INVISIBLE）中给出了NullPointerException 请建议。谢谢代码：

ImageView iv4;
    public void onCreate(Bundle savedInstanceState) {
            requestWindowFeature(Window.FEATURE_NO_TITLE);
            getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_score);
            iv4= (ImageView) findViewById(R.id.imageView4);
            iv4.setVisibility(View.INVISIBLE);
        }

<RelativeLayout 
   xmlns:android="schemas.android.com/apk/res/android"; 
   android:id="@+id/RelativeLayout1" 
   android:layout_width="match_parent" 
   android:layout_height="match_parent"> 

 <ImageView android:id="@+id/imageView4" 
      android:layout_width="110dp" 
      android:layout_height="110dp" 
      android:layout_alignParentRight="true" 
      android:layout_alignParentTop="true" 
      android:src="@drawable/hg" /> 
  </RelativeLayout>

堆栈跟踪如下：

03-05 03:49:25.477: E/AndroidRuntime(1070): FATAL EXCEPTION: main
03-05 03:49:25.477: E/AndroidRuntime(1070): java.lang.RuntimeException: Unable to start activity ComponentInfo{bitcream.candyhive.candy/bitcream.candyhive.candy.ScoreActivity}: java.lang.NullPointerException
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.os.Looper.loop(Looper.java:123)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread.main(ActivityThread.java:3683)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at java.lang.reflect.Method.invokeNative(Native Method)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at java.lang.reflect.Method.invoke(Method.java:507)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at dalvik.system.NativeStart.main(Native Method)
03-05 03:49:25.477: E/AndroidRuntime(1070): Caused by: java.lang.NullPointerException
03-05 03:49:25.477: E/AndroidRuntime(1070):     at bitcream.candyhive.candy.ScoreActivity.onCreate(ScoreActivity.java:42)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-05 03:49:25.477: E/AndroidRuntime(1070):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
03-05 03:49:25.477: E/AndroidRuntime(1070):     ... 11 more
03-05 03:49:28.297: I/Process(1070): Sending signal. PID: 1070 SIG: 9

Answer 1

行iv4.setVisibility（View.INVISIBLE）中的NullPointerException

ImageView中可能没有imageView4代码activity_score.xml。

您引用了错误的布局，或者您的布局不包含带有ID的图像视图。

编辑：

更改

<RelativeLayout 
xmlns:android="schemas.android.com/apk/res/android"

到

<RelativeLayout 
 xmlns:android="http://schemas.android.com/apk/res/android"

如果NullPointerException找不到当前虚增布局中提到的ID的视图，您将获得findViewById。

使imageview不可见会导致NullPointerException

1 个答案: