我试图随机生成一个方程，也有50%的机会是错误的，并显示不正确的答案。不正确的答案应该有一个错误-2、-1、+1或+2。
有时我的代码会打印这样的除法方程（我不能发布图像）：2/10=13 1/5=43等等。
我搞不懂为什么这个等式显示的是一组没有一起检查的数字？
（它首先调用oncreateview方法中的generateEnumbers（）

public void generateNumbers() {
    //randomly generate 2 numbers and an operator
    number1 = (int) (Math.random() * 10) + 1;
    number2 = (int) (Math.random() * 10) + 1;
    operator = (int) (Math.random() * 4) + 1;
    //50% chance whether the displayed answer will be right or wrong
    rightOrWrong = (int) (Math.random() * 2) + 1;
    //calculate the offset of displayed answer for a wrong equation (Error)
    error = (int) (Math.random() * 4) + 1;
    generateEquation();
}

public void generateEquation() {
    StringBuilder equation = new StringBuilder();
    //append the first number
    equation.append(number1);
    //generate/append the operator and calculate the real answer
    if (operator == 1) {
        equation.append(" + ");
        actualAnswer = number1 + number2;
    } else if (operator == 2) {
        equation.append(" - ");
        actualAnswer = number1 - number2;
    } else if (operator == 3) {
        equation.append(" x ");
        actualAnswer = number1 * number2;
    } else if (operator == 4) {
        if ((number1%number2==0) && (number1>number2)) {
            actualAnswer = number1 / number2;
        } else {
            generateNumbers();
        }
        equation.append(" / ");

    }
    //append the second number and the equals sign
    equation.append(number2 + " = ");

    //we will display the correct answer for the equation
    if (rightOrWrong == 1) {
        displayedAnswer = actualAnswer;
        equation.append(displayedAnswer);
    }
    //we will display an incorrect answer for the equation
    //need to calculate error (-2, -1, +1, +2)
    else {
        if (error == 1) {
            displayedAnswer = actualAnswer - 1;
        } else if (error == 2) {
            displayedAnswer = actualAnswer - 2;
        }else if (error == 3) {
            displayedAnswer = actualAnswer + 1;
        }else {
            displayedAnswer = actualAnswer + 2;
        }
        //append the displayed answer with error
        equation.append(displayedAnswer);

    }
    questionNumber.setText("You have answered " + count + " out of 20 questions");
    finalEquation.setText(equation.toString());
}