问题
While implementing Twitter integration in my app, I discovered the following oddness of the Eclipse debugger. What is causing this?
I'm using this AsyncTask for getting a request token from twitter using twitter4j 3.0.3.
public class TwitterRequestAsync extends AsyncTask<Void, Void, RequestToken> {
private Context context;
public TwitterRequestAsync(Context context) {
this.context = context;
}
@Override
protected RequestToken doInBackground( Void... params ) {
Twitter twitter = getTwitter(); // getTwitter() is in enclosing class
try {
RequestToken token = twitter.getOAuthRequestToken();
return token;
}
catch (TwitterException e) {
Log.e( TAG, e.getMessage(), e );
return null;
}
}
@Override
protected void onPostExecute( RequestToken result ) {
super.onPostExecute( result );
if ( result != null ) {
// stuffs concerning request token here
}
}
}
When I debug this code it appears that there is an exception thrown when getOAuthRequestToken() executes and the next line that the debugger shows executing is in the catch clause, return null;
However, the result that is returned to onPostExecute(...) is a valid request token, so the debugger is doing something weird. I've cleaned my project and restarted Eclipse each multiple times with no change in this behavior. Am I broken?
回答1:
This is a known issue. It appears that it could be a problem with the Dalvik VM. The last return statement of the method is shown to execute in the debugger.
Changing the doInBackground body to:
@Override
protected RequestToken doInBackground( Void... params ) {
Twitter twitter = getTwitter();
RequestToken token = null;
try {
token = twitter.getOAuthRequestToken();
}
catch (TwitterException e) {
Log.e( TAG, e.getMessage(), e );
}
return token;
}
Causes execution to appear to proceed as expected.
See https://groups.google.com/forum/?fromgroups=#!topic/android-developers/DEU6JmdyFyM for an old mention of the problem with a link to an even older mention. Someone finally created an issue for this at https://code.google.com/p/android/issues/detail?id=34193.
回答2:
As your self-answer notes, this is a known issue. I wanted to point out that it (and other quirks) are documented in the Dalvik docs. You can find it in the official but raw form, or unofficial but formatted -- skip down to "Known Issues and Limitations".
It would be nice if the documentation was more prominent.
来源：https://stackoverflow.com/questions/15604674/eclipse-debugging-android-app-debugger-shows-wrong-line-executing