Android 应用程序强制关闭错误

Question

I have added the Results class to the Android Manifest, so yes, you can cross that off the list. Is it an error in the way I've set out the method?

    package com.kenning.foreveralone;


    import android.app.Activity;
    import android.os.Bundle;
    import android.widget.EditText;
    import android.widget.TextView;

    public class Results extends Activity{

        EditText fbFriends;
        TextView resulting;
        String value;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            // TODO Auto-generated method stub
            super.onCreate(savedInstanceState);
            setContentView(R.layout.rslt);
            TextView resulting = (TextView) findViewById(R.id.result);
            EditText fbFriends = (EditText) findViewById(R.id.noFacebookFriends);
            String value = fbFriends.getText().toString();
            resulting.setText("Your score is " + value);
        }



    }

When I start this class, it always seems to force close my app. Can anyone tell me what I'm doing wrong?

Here's the log cat:

04-08 20:05:24.169: E/AndroidRuntime(589): FATAL EXCEPTION: main
04-08 20:05:24.169: E/AndroidRuntime(589): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kenning.foreveralone/com.kenning.foreveralone.Results}: java.lang.NullPointerException
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.os.Handler.dispatchMessage(Handler.java:99)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.os.Looper.loop(Looper.java:123)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread.main(ActivityThread.java:4627)
04-08 20:05:24.169: E/AndroidRuntime(589):  at java.lang.reflect.Method.invokeNative(Native Method)
04-08 20:05:24.169: E/AndroidRuntime(589):  at java.lang.reflect.Method.invoke(Method.java:521)
04-08 20:05:24.169: E/AndroidRuntime(589):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-08 20:05:24.169: E/AndroidRuntime(589):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-08 20:05:24.169: E/AndroidRuntime(589):  at dalvik.system.NativeStart.main(Native Method)
04-08 20:05:24.169: E/AndroidRuntime(589): Caused by: java.lang.NullPointerException
04-08 20:05:24.169: E/AndroidRuntime(589):  at com.kenning.foreveralone.Results.onCreate(Results.java:20)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-08 20:05:24.169: E/AndroidRuntime(589):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
04-08 20:05:24.169: E/AndroidRuntime(589):  ... 11 more

Answer 1

You are getting a NullPointerException somewhere in your OnCreate. I am guessing that either the ids are wrong in your rslt.xml layout so result and fbFriends is null, or fbFriends doesn't have any text in it so getText() returns null.

Answer 2

It's a null pointer exception in onCreate, so why not try stepping through onCreate to see what variable is null?

That said, I'm guessing R.id.noFacebookFriends is not part of the R.layout.rslt .