NullPointerException at Home.onCreate

I am trying to run a test program that allows a user to click a button and move to a different screen. I have the Home(First Activity) and Away(Second Activity) classes and a xml file specifying the layout for each. My source code is as follows:

public class Home extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Button create = (Button)findViewById(R.id.create);
    create.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v)
    {
        Intent intent = new Intent(Home.this, Away.class);
        startActivity(intent);
    }
});


    setContentView(R.layout.main);
}

}

And Away.java

public class Away extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.away);
}
}

I get a NullPointerException in the DDMS trace

at Home.onCreate(line 17)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at and开发者_如何学Goroid.app.ActivityThread.performLaunchActivity(ActivityThread.java: 2627)

Anyone see anything in my code that may be causing this?

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findViewById() traverses the view hierarchy set up when setContentView() inflates your layout. You cannot retrieve a reference to a view in your XML before you have called setContentView(). Change your onCreate() method in Home to look like this:

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  //Call me first
  setContentView(R.layout.main);

  Button create = (Button)findViewById(R.id.create);
  create.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v)
    {
      Intent intent = new Intent(Home.this, Away.class);
      startActivity(intent);
    }
  });
}

Otherwise, findViewById() will return null because there are no views in the tree...thus, a view with your requested id value doesn't exist.

Hope that helps!

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If the findViewById call can't find the actual thing you are looking for, it could return a null object and cause the call to setOnClickListener to throw an NPE. Are you sure you've got the right ID (R.id.create) specified?