我正在使用一个名为注销的按钮。此注销适用于应用程序中用户的 facebook 注销选项。当我单击此按钮时，出现以下错误。
我在下面的代码中注释了出现此错误的行。
09-11 15:25:30.124: E/AndroidRuntime(6866): FATAL EXCEPTION: main
> 09-11 15:25:30.124: E/AndroidRuntime(6866):
> java.lang.NullPointerException 09-11 15:25:30.124:
> E/AndroidRuntime(6866): at
> com.example.settings.Settings$1.logout(Settings.java:46) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> com.example.settings.Settings$1.onClick(Settings.java:38) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> android.view.View.performClick(View.java:2485) 09-11 15:25:30.124:
> E/AndroidRuntime(6866): at
> android.view.View$PerformClick.run(View.java:9080) 09-11 15:25:30.124:
> E/AndroidRuntime(6866): at
> android.os.Handler.handleCallback(Handler.java:587) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> android.os.Handler.dispatchMessage(Handler.java:92) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> android.os.Looper.loop(Looper.java:123) 09-11 15:25:30.124:
> E/AndroidRuntime(6866): at
> android.app.ActivityThread.main(ActivityThread.java:3683) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> java.lang.reflect.Method.invokeNative(Native Method) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> java.lang.reflect.Method.invoke(Method.java:507) 09-11 15:25:30.124:
> E/AndroidRuntime(6866): at
> com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
> 09-11 15:25:30.124: E/AndroidRuntime(6866): at
> com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 09-11
> 15:25:30.124: E/AndroidRuntime(6866): at
> dalvik.system.NativeStart.main(Native Method)
我的代码：
脸书脸书；
Button btn_logout = (Button)findViewById(R.id.logout);
btn_logout.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
String response = logout();//error
Toast.makeText(getApplicationContext(), "Logout"+ response , 2).show();
}
public String logout() {
// TODO Auto-generated method stub
String res = null;
try {
res = fb.logout(getApplicationContext());//error
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return res;
}
});