Android sdk:java.lang.NullPointerException:尝试调用虚方法

Question

当我尝试在我的设备上调试应用程序并尝试在几个小时内摆脱它时,我收到此错误...并且无法弄清楚...如果有人能找到解决方案,那将是非常棒的,因为我想要尽快为我的应用发布新的更新..

07-05 22:45:02.550    2821-2821/davvarn.csgo_maps E/AndroidRuntime? FATAL EXCEPTION: main
    Process: davvarn.csgo_maps, PID: 2821
    java.lang.RuntimeException: Unable to start activity ComponentInfo{davvarn.csgo_maps/davvarn.csgo_maps.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageDrawable(android.graphics.drawable.Drawable)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2356)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2418)
            at android.app.ActivityThread.access$900(ActivityThread.java:154)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5289)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageDrawable(android.graphics.drawable.Drawable)' on a null object reference
            at davvarn.csgo_maps.MainActivity.changeContent(MainActivity.java:176)
            at davvarn.csgo_maps.MainActivity.onCreate(MainActivity.java:115)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2309)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2418)
            at android.app.ActivityThread.access$900(ActivityThread.java:154)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5289)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)

我真的不知道如何粘贴MainActivity文件,因为我是Stackoverflow的新手.请让我知道如何,我会尝试.

Answer 1

确保已初始化图像视图并使用XML中定义的正确ID.您可以像这样初始化ImageView:

ImageView imageView = (ImageView)findViewById(R.id.yourImageViewIDHere);

在onCreate调用setContentView之后,请执行此操作.