问题描述
我有一个初学者问题,我想调试我的应用程序,但我不知道如何正确使用 Logcat.
I have a beginner question, I want to debug my app and i don't know how to use the Logcat properly.
现在,我收到了这个错误,我不知道这是什么意思.
Right now, I am getting this error and i don't know what it means.
我如何使用这些信息?有可以看的教程吗?
How can i use this information?Is there a tutorial somewhere i can watch?
感谢您的帮助.
09-23 11:27:55.968: E/AndroidRuntime(807): FATAL EXCEPTION: main
09-23 11:27:55.968: E/AndroidRuntime(807): java.lang.NullPointerException
09-23 11:27:55.968: E/AndroidRuntime(807): at com.uniqueapps.runner.Start.onClick(Start.java:49)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.view.View.performClick(View.java:4240)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.view.View$PerformClick.run(View.java:17721)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.os.Handler.handleCallback(Handler.java:730)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.os.Handler.dispatchMessage(Handler.java:92)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.os.Looper.loop(Looper.java:137)
09-23 11:27:55.968: E/AndroidRuntime(807): at android.app.ActivityThread.main(ActivityThread.java:5103)
09-23 11:27:55.968: E/AndroidRuntime(807): at java.lang.reflect.Method.invokeNative(Native Method)
09-23 11:27:55.968: E/AndroidRuntime(807): at java.lang.reflect.Method.invoke(Method.java:525)
09-23 11:27:55.968: E/AndroidRuntime(807): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-23 11:27:55.968: E/AndroidRuntime(807): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-23 11:27:55.968: E/AndroidRuntime(807): at dalvik.system.NativeStart.main(Native Method)
09-23 11:27:59.528: I/Process(807): Sending signal. PID: 807 SIG: 9
09-23 11:28:01.108: D/gralloc_goldfish(877): Emulator without GPU emulation detected.
09-23 11:54:55.318: D/gralloc_goldfish(937): Emulator without GPU emulation detected.
09-23 11:54:57.887: I/Choreographer(937): Skipped 35 frames! The application may be doing too much work on its main thread.
09-23 11:55:03.118: D/dalvikvm(937): GC_FOR_ALLOC freed 89K, 7% free 2928K/3136K, paused 39ms, total 72ms
09-23 11:55:05.858: D/AndroidRuntime(937): Shutting down VM
09-23 11:55:05.858: W/dalvikvm(937): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
09-23 11:55:05.868: E/AndroidRuntime(937): FATAL EXCEPTION: main
09-23 11:55:05.868: E/AndroidRuntime(937): java.lang.NullPointerException
09-23 11:55:05.868: E/AndroidRuntime(937): at com.uniqueapps.runner.Start.onClick(Start.java:49)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.view.View.performClick(View.java:4240)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.view.View$PerformClick.run(View.java:17721)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.os.Handler.handleCallback(Handler.java:730)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.os.Handler.dispatchMessage(Handler.java:92)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.os.Looper.loop(Looper.java:137)
09-23 11:55:05.868: E/AndroidRuntime(937): at android.app.ActivityThread.main(ActivityThread.java:5103)
09-23 11:55:05.868: E/AndroidRuntime(937): at java.lang.reflect.Method.invokeNative(Native Method)
09-23 11:55:05.868: E/AndroidRuntime(937): at java.lang.reflect.Method.invoke(Method.java:525)
09-23 11:55:05.868: E/AndroidRuntime(937): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-23 11:55:05.868: E/AndroidRuntime(937): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-23 11:55:05.868: E/AndroidRuntime(937): at dalvik.system.NativeStart.main(Native Method)
09-23 11:55:09.657: D/gralloc_goldfish(961): Emulator without GPU emulation detected.
09-23 12:04:20.418: D/gralloc_goldfish(1006): Emulator without GPU emulation detected.
09-23 12:04:27.118: D/dalvikvm(1006): GC_FOR_ALLOC freed 96K, 7% free 2919K/3136K, paused 40ms, total 72ms
09-23 12:04:30.337: D/AndroidRuntime(1006): Shutting down VM
09-23 12:04:30.357: W/dalvikvm(1006): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
09-23 12:04:30.397: E/AndroidRuntime(1006): FATAL EXCEPTION: main
09-23 12:04:30.397: E/AndroidRuntime(1006): java.lang.NullPointerException
09-23 12:04:30.397: E/AndroidRuntime(1006): at com.uniqueapps.runner.Start.onClick(Start.java:49)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.view.View.performClick(View.java:4240)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.view.View$PerformClick.run(View.java:17721)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.os.Handler.handleCallback(Handler.java:730)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.os.Handler.dispatchMessage(Handler.java:92)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.os.Looper.loop(Looper.java:137)
09-23 12:04:30.397: E/AndroidRuntime(1006): at android.app.ActivityThread.main(ActivityThread.java:5103)
09-23 12:04:30.397: E/AndroidRuntime(1006): at java.lang.reflect.Method.invokeNative(Native Method)
09-23 12:04:30.397: E/AndroidRuntime(1006): at java.lang.reflect.Method.invoke(Method.java:525)
09-23 12:04:30.397: E/AndroidRuntime(1006): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-23 12:04:30.397: E/AndroidRuntime(1006): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-23 12:04:30.397: E/AndroidRuntime(1006): at dalvik.system.NativeStart.main(Native Method)
09-23 12:04:33.918: D/gralloc_goldfish(1030): Emulator without GPU emulation detected.
推荐答案
看到之后
FATAL EXCEPTION: main
你会看到问题,这里是一个NPE
you will see the problem, here a NPE
09-23 11:27:55.968: E/AndroidRuntime(807): java.lang.NullPointerException
然后您会找到引用您的应用的第一行.这是下面这行
then you find the first line that references your app. Here it is the following line
at com.uniqueapps.runner.Start.onClick(Start.java:49)
这表示在 Start.java
中的 null
在第 49 行的 onClick()
中.所以你去那行看看什么可能是null
...就像一个试图访问一个方法的变量,例如setText()
、getText()
,或任何 Android 或用户定义的方法.有时它是 null
的原因很简单,有时您必须进一步追溯以查看是什么使它成为 null
.
This says that in Start.java
something is null
in onClick()
at line 49. So you go to that line and see what could be null
...like a variable that tries to access a method such as setText()
, getText()
, or any Android or user defined method. Sometimes it is simple why it is null
and sometimes you have to trace back further to see what makes it null
.
编辑
如果一个变量是null
,那是因为它没有正确初始化,或者根本没有初始化.所以也许你有一个变量 TextView tv;
但你从来没有通过做类似的事情给它一个值
If a variable is null
it is because it hasn't been initialized properly, or at all. So maybe you have a variable TextView tv;
but you never gave it a value by doing something like
tv = (TextView) findViewById(R.id.myTV);
如果你尝试做类似 tv.setText("Some Text");
你会得到一个 NPE
因为你没有用类似的东西初始化它上面的代码行.或者,您可能尝试初始化它并使用了错误的 id
,就像来自不同 layout
的一样.这将返回 null
并以相同的方式创建一个 NPE
.这可以在您尝试调用方法的任何变量上.
if you try to do something like tv.setText("Some Text");
you will get a NPE
because you didn't initialize it with something like the above line of code. Or maybe you tried to initialize it and used the wrong id
like one from a different layout
. This will return null
and create a NPE
in the same way. This can be on any variable that you try to call a method on.
这篇关于Eclipse logcat 调试的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!