diff --git a/SoftwareDesign/Code/2-2-5_enhanced/mainwindow.cpp b/SoftwareDesign/Code/2-2-5_enhanced/mainwindow.cpp
index 4ae1ea6..0859933 100644
--- a/SoftwareDesign/Code/2-2-5_enhanced/mainwindow.cpp
+++ b/SoftwareDesign/Code/2-2-5_enhanced/mainwindow.cpp
@@ -22,8 +22,8 @@ void MainWindow::abortOperation() {
   result = 0.0;
   pendingOperator.clear();
   ui->lineEdit->setText("0");
-  waitForOperand = true;
-  QMessageBox::warning(this, "运算错误", "除数不能为零");
+  isFinished = false;
+  QMessageBox::warning(this, "运算错误", "算式不合法");
 }
 
 //数字被点击
@@ -55,7 +55,13 @@ void MainWindow::on_clearAllBtn_clicked() {
 }
 
 void MainWindow::on_equalBtn_clicked() {
-  result = cal(displayText.toStdString());
+  try {
+    result = cal(displayText.toStdString());
+  }
+
+  catch (...) {
+    abortOperation();
+  }
   isFinished = 1;
   ui->lineEdit->setText(QString::number(result));
 }