volley 发送post请求

public static void postNewComment(Context context,final UserAccount userAccount,final String comment,final int blogId,final int postId){
mPostCommentResponse.requestStarted();
RequestQueue queue = Volley.newRequestQueue(context);
StringRequest sr = new StringRequest(Request.Method.POST,"http://api.someservice.com/post/comment", new Response.Listener<String>() {
@Override
public void onResponse(String response) {
mPostCommentResponse.requestCompleted();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
mPostCommentResponse.requestEndedWithError(error);
}
}){
@Override
protected Map<String,String> getParams(){
Map<String,String> params = new HashMap<String, String>();
params.put("user",userAccount.getUsername());
params.put("pass",userAccount.getPassword());
params.put("comment", Uri.encode(comment));
params.put("comment_post_ID",String.valueOf(postId));
params.put("blogId",String.valueOf(blogId));

return params;
}

@Override
public Map<String, String> getHeaders() throws AuthFailureError {
Map<String,String> params = new HashMap<String, String>();
params.put("Content-Type","application/x-www-form-urlencoded");
return params;
}
};
queue.add(sr);
}

public interface PostCommentResponseListener {
public void requestStarted();
public void requestCompleted();
public void requestEndedWithError(VolleyError error);
}