Java Android开发工具-错误

我是个新手，我需要一些ADT方面的帮助。=）

我创建了一个新的android应用程序项目，并在我的设备上做了一个测试，没有更改任何文件，效果很好。（它显示了hello world）。但是，在我尝试添加按钮和文本视图之后，当我在Nexus5设备上运行时，不幸的是，HelloWord停止了

（res->layout->**activity_main.xml）和**

请帮助=）

用圆木

04-07 22:04:41.290: W/dalvikvm(27947): threadid=1: thread exiting with uncaught exception (group=0x41597ba8)
04-07 22:04:41.290: E/AndroidRuntime(27947): FATAL EXCEPTION: main
04-07 22:04:41.290: E/AndroidRuntime(27947): Process: com.example.helloworld, PID: 27947
04-07 22:04:41.290: E/AndroidRuntime(27947): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.helloworld/com.example.helloworld.MainActivity}: java.lang.NullPointerException
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.os.Handler.dispatchMessage(Handler.java:102)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.os.Looper.loop(Looper.java:136)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.main(ActivityThread.java:5017)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at java.lang.reflect.Method.invokeNative(Native Method)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at java.lang.reflect.Method.invoke(Method.java:515)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at dalvik.system.NativeStart.main(Native Method)
04-07 22:04:41.290: E/AndroidRuntime(27947): Caused by: java.lang.NullPointerException
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.example.helloworld.MainActivity.onCreate(MainActivity.java:27)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.Activity.performCreate(Activity.java:5231)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-07 22:04:41.290: E/AndroidRuntime(27947):    ... 11 more

---

您正在调用

TextView tv=（TextView）findViewById（R.id.TextView1）

，但在布局中，

TextView

被称为

textView1

，因此，它返回

null

，您可能会得到

NullPointerException

。请注意这种情况，因为它们在Android中起着不同的作用（区分大小写）。

您正在调用

TextView tv=（TextView）findViewById（R.id.TextView 1）

，但在布局中，

TextView

被称为

textView1

，因此，它返回

null

，您可能会得到

NullPointerException

。请注意这种情况，因为它们在Android中会有所不同（区分大小写）。

用实际完整的Logcat堆栈跟踪更新您的问题MainActivity.java文件的第27行是什么？用实际完整的Logcat堆栈跟踪更新您的问题MainActivity.java文件的第27行是什么？

Button btn = (Button) findViewById(R.id.button1);
TextView tv = (TextView) findViewById(R.id.TextView1);
btn.setOnClickListener(new onClickListener(){
@Override
public void OnClick(View v){
   tv.setText("Clicked");
}});

04-07 22:04:41.290: W/dalvikvm(27947): threadid=1: thread exiting with uncaught exception (group=0x41597ba8)
04-07 22:04:41.290: E/AndroidRuntime(27947): FATAL EXCEPTION: main
04-07 22:04:41.290: E/AndroidRuntime(27947): Process: com.example.helloworld, PID: 27947
04-07 22:04:41.290: E/AndroidRuntime(27947): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.helloworld/com.example.helloworld.MainActivity}: java.lang.NullPointerException
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.os.Handler.dispatchMessage(Handler.java:102)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.os.Looper.loop(Looper.java:136)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.main(ActivityThread.java:5017)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at java.lang.reflect.Method.invokeNative(Native Method)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at java.lang.reflect.Method.invoke(Method.java:515)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at dalvik.system.NativeStart.main(Native Method)
04-07 22:04:41.290: E/AndroidRuntime(27947): Caused by: java.lang.NullPointerException
04-07 22:04:41.290: E/AndroidRuntime(27947):    at com.example.helloworld.MainActivity.onCreate(MainActivity.java:27)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.Activity.performCreate(Activity.java:5231)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-07 22:04:41.290: E/AndroidRuntime(27947):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-07 22:04:41.290: E/AndroidRuntime(27947):    ... 11 more