Android:BufferedReader“；“瞬间崩溃”；

当代码中声明了

BufferedReader

时，为什么它喜欢立即崩溃并说“x一直停止”

这是目前的代码（不是全部）：

从日志猫：

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: de.kurt.vertretungsplan, PID: 4525
              java.lang.RuntimeException: Unable to start activity ComponentInfo{de.kurt.vertretungsplan/de.kurt.vertretungsplan.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.InputStream java.net.URL.openStream()' on a null object reference
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.InputStream java.net.URL.openStream()' on a null object reference
                  at de.kurt.vertretungsplan.MainActivity.onCreate(MainActivity.java:89)
                  at android.app.Activity.performCreate(Activity.java:6679)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6119) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) E/libEGL: validate_display:99 error 3008 (EGL_BAD_DISPLAY)

---

您认为问题出在哪里？

。您应该至少有两个：一个是触发您正在看到的对话框的，另一个是从

try

/

catch

块（因为您似乎试图在主应用程序线程上执行网络I/O）。我从LogCat添加了一些文本，谢谢

url

将显示为

null

。它也不是这样工作的：尝试{url url url=new url（“）；BufferedReader in=new BufferedReader（new InputStreamReader（url.openStream（））；}catch（IOException e）{e.printStackTrace（）；}很可能，您现在有了不同的Java堆栈跟踪。

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: de.kurt.vertretungsplan, PID: 4525
              java.lang.RuntimeException: Unable to start activity ComponentInfo{de.kurt.vertretungsplan/de.kurt.vertretungsplan.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.InputStream java.net.URL.openStream()' on a null object reference
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.InputStream java.net.URL.openStream()' on a null object reference
                  at de.kurt.vertretungsplan.MainActivity.onCreate(MainActivity.java:89)
                  at android.app.Activity.performCreate(Activity.java:6679)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6119) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) E/libEGL: validate_display:99 error 3008 (EGL_BAD_DISPLAY)