Android计算器无法解决某些方程式

Question

大家好，我有这个Android计算器，它包含2个文本视图命名，计算器（所有计算发生，visibilty设置为无敌）和texview（显示方程）。算术运算符似乎运行良好，例如3 + 3 + 5 = 11,5 + 5-1 = 9,5 / 5-1 = 0。我遇到的问题是，无论何时方程看起来像上面的例子，它给出了正确的答案，但当我有3-2 + 1,5,5 + 1,2 + 2/4的东西时，我得到了非常错误的答案。相关按钮的代码是......

        button1.Click += delegate {
            textveiw.Text += button1.Text;
            calculator.Text += button1.Text;
            if (equalToClick==true){
                total1=0;
                total2=0;
                calculator.Text="";
                calculator.Text += button1.Text;
                textveiw.Text=button1.Text;
                equalToClick=false;
            }
        };
        plus.Click += delegate {
        textveiw.Text += plus.Text;            
   total1=total1+double.Parse
   (calculator.Text);
        calculator.Text=("");
            equalToClick=false;
         operatorSelected="+";
            plusClick=true;

        };
        sub.Click += delegate {
            textveiw.Text += sub.Text;    
    total1=total1+double.Parse
    (calculator.Text);
            calculator.Text=("");
            equalToClick=false;
            operatorSelected="-";
            subClick = true;
         };
        multiplication.Click += delegate {
        textveiw.Text += multiplication.Text;
        total1= total1+double.Parse
   (calculator.Text);
         calculator.Text=("");
         equaltoclick=false;
         operatorSelected="*";
         mulClick = true;

        };
        divide.Click += delegate {
            textveiw.Text += divide.Text;
            total1 = total1 + double.Parse
     (calculator.Text);
            calculator.Text=("");
            equalToClick=false;
            operatorSelected="/";
            divClick = true;

        };
        //equals button
        equalto.Click+=delegate {
            switch(operatorSelected)
            {

            case "+" :
                total2=total1+double.Parse
       (calculator.Text);
                textveiw.Text=total2.ToString();
                equalToClick=true;
                plusClick=false;
                break;

            case "-":
                total2=total1 - double.Parse
       (calculator.Text);
                textveiw.Text=total2.ToString();
                equalToClick=true;
                subClick=false;
                break;
            case "*":
                total2=total1 * double.Parse
       (calculator.Text);
                textveiw.Text=total2.ToString();
                equalToClick=true;
                mulClick=false;
                break;

             case "/":

                total2=total1 / double.Parse
       (calculator.Text);
                textveiw.Text=total2.ToString();
                equalToClick=true;
                divClick=false;
                break;

                default :
                if(subClick==false && 
         plusClick==false && 
        mulClick==false && 
        divClick==false){
                    Toast.MakeText
   (this,"please select an   
   operator",ToastLength.Short)
   .Show();
                }
                break;

                }
            };

        cancel.Click += delegate {
            textveiw.Text=("");
            calculator.Text=("");
            total1=0;
            total2=0;


        };