android 这段代码啥意思？

Question

public void callResult(MtopResult result) {
        Message msg = Message.obtain();
        msg.what = 500;
        msg.obj = result;
        this.mHandler.sendMessage(msg);
    }

    public boolean handleMessage(Message msg) {
        switch (msg.what) {
            case 0:
                if (this.isUserLogin) {
                    MtopResult result = new MtopResult();
                    result.addData(ApiConstants.RET, new JSONArray().put("ERR_SID_INVALID"));
                    if (this.jsContext instanceof WVCallBackContext) {
                        ((WVCallBackContext) this.jsContext).error(result.toString());
                    }
                    if (TaoLog.getLogStatus()) {
                        TaoLog.d("WVServer", "login fail, call result, " + result.toString());
                    }
                    this.isUserLogin = false;
                }
                notifyNext();
                return true;
            case 1:
                notifyNext();
                this.isUserLogin = false;
                this.singleExecutor.execute(new ServerRequestTask(this.jsContext, this.mParams));
                if (!TaoLog.getLogStatus()) {
                    return true;
                }
                TaoLog.d("WVServer", "login success, execute task, mParams:" + this.mParams);
                return true;
            case 500:
                if (msg.obj instanceof MtopResult) {
                    MtopResult result2 = (MtopResult) msg.obj;
                    if (result2.isSuccess()) {
                        if (result2.getJsContext() instanceof WVCallBackContext) {
                            ((WVCallBackContext) result2.getJsContext()).success(result2.toString());
                        }
                    } else if (result2.getJsContext() instanceof WVCallBackContext) {
                        ((WVCallBackContext) result2.getJsContext()).error(result2.toString());
                    }
                    if (TaoLog.getLogStatus()) {
                        TaoLog.d("WVServer", "call result, retString: " + result2.toString());
                    }
                }
                notifyNext();
                return true;
            case NOT_REG_LOGIN /*510*/:
                MtopResult result3 = new MtopResult();
                result3.addData(ApiConstants.RET, new JSONArray().put("HY_FAILED"));
                result3.addData("code", "-1");
                if (this.jsContext instanceof WVCallBackContext) {
                    ((WVCallBackContext) this.jsContext).error(result3.toString());
                }
                if (TaoLog.getLogStatus()) {
                    TaoLog.d("WVServer", "not reg login, call fail, " + result3.toString());
                }
                notifyNext();
                return true;
            default:
                return false;
        }
    }

这里的WVCALLBACKCONTEXT 估计是啥意思？