我一直在關注官方Android Dev站點上的Android Studio培訓教程,以創建一個簡單的「消息傳遞」應用程序(link to tutorial)。我達成了「構建我的第一個應用程序」的結尾。當我點擊「發送按鈕」應用程序崩潰時,消息的內容是無關緊要的。我已經在我的手機和模擬器上試過了。 這裏的錯誤代碼:按鈕導致崩潰
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.john.myfirstapp, PID: 3180
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.john.myfirstapp/com.john.myfirstapp.DisplayMessageActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference
at com.john.myfirstapp.DisplayMessageActivity.<init>(DisplayMessageActivity.java:16)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1067)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Android Studio中也給了我在這條線的建議:
getSupportActionBar()setDisplayHomeAsUpEnabled(真);
它指出:
方法調用 'getSupportActionBar()setDisplayHomeAsUpEnabled(真)' 可能會產生 '顯示java.lang.NullPointerException'
我相當肯定,它不是像捲曲或缺少報價那樣的小錯誤。
任何幫助表示讚賞:)
崩潰發生在這裏:DisplayMessageActivity.java線16 ...份額DisplayMessageActivity.java源代碼 – W0rmH0le