篇首语：本文由编程笔记#自由互联小编为大家整理，主要介绍了报错java.lang.RuntimeException:xxxx(项目文件目录)：xxx ... on a null object reference相关的知识，希望对你有一定的参考价值。
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关于android stdio空指针报错
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Process: com.example.express.g, PID: 11002 java.lang.RuntimeException: Unable to start activity ComponentInfocom.example.express.g/com.example.express.activity.UserMainActivity: java.lang.NullPointerException: Attempt to invoke virtual method void android.widget.TextView.setTextColor(int) on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method void android.widget.TextView.setTextColor(int) on a null object reference at com.example.express.activity.UserMainActivity.setFragment(UserMainActivity.java:77) at com.example.express.activity.UserMainActivity.onCreate(UserMainActivity.java:40) at android.app.Activity.performCreate(Activity.java:7994) at android.app.Activity.performCreate(Activity.java:7978) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
然后呢自由互联小编就发现
这个地方为空值所以顺着逻辑向上找发现没有获取控件信息无语至极 
更要命的是这一次给那个获取控件信息放在使用的后边也报空指针无了个大语真就日八歘。 
总结
一般情况下呢我们遇到空指针的时候肯定是某个地方我们所用到的变量没有告知编译器他自己不晓得那个东西是啥子就卡在那里耍脾气可以通过他那个报错定位或者调试定位到具体的问题处然后就这样这样那样那样就over咯。 