Question

首先使用eclipse。我正在构建一个Android计算器。我有我的所有代码，除了有问题。我的一个变量没有被使用。我的total1变量基本上是程序的计数器。当我添加两个数字并按下等号时，它总是打印“0.0”，这是total1的值。这意味着由于某种原因，它在整个计划中从未改变过。我甚至使用print语句对此进行了测试。我更改了total1的值，它将打印我指定给它的值。可能是什么问题？

public class HelloAndroidActivity extends Activity {
    public EditText display;
    String display1;
    double displayValue;

    // Program is printing out total1, as if it weren't maninpulated in the code
    double total1 = 0.0;
    double total2 = 0.0;

    char theOperator;
    public String buttonText;
    public Button ButtonAdd, ButtonEqual, ButtonMultiply, ButtonDivide, ButtonMinus;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        display = (EditText) findViewById(R.id.editText1);

        // Could it have something to do with this if statement?
        if (display.length() != 0) {
            display1 = display.getText().toString();
            displayValue = Double.parseDouble(display1);
        }
    }

    //Get the operator of the multiply, divide, subtract, add buttons when they are clicked and then do the following
    public void getOperator(String btnText) {
        theOperator = btnText.charAt(0);

        total1 += displayValue;
        display.setText("");
    }

    // Display a string in the box when a number button is clicked
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.bOne:
            display.append("1");        
            break;
        case R.id.bTwo:
            display.append("2");
            break;
        case R.id.bThree:
            display.append("3");
            break;
        case R.id.bFour:
            display.append("4");
            break;
        case R.id.bFive:
            display.append("5");
            break;
        case R.id.bSix:
            display.append("6");
            break;
        case R.id.bSeven:
            display.append("7");
            break;
        case R.id.bEight:
            display.append("8");
            break;
        case R.id.bNine:
            display.append("9");
            break;
        case R.id.bZero:
            display.append("0");
            break;
        case R.id.bPoint:
            display.append(".");
            break;
        case R.id.bClear:
            total2 = 0.0;
            display.setText("");
            break;
        case R.id.bAdd:
            buttonText = "+";
            ButtonAdd = (Button) findViewById(R.id.bAdd);
            ButtonAdd.setText(buttonText);
            getOperator(buttonText);
            break;
        case R.id.bMinus:
            buttonText = "-";
            ButtonMinus = (Button) findViewById(R.id.bMinus);
            ButtonMinus.setText(buttonText);
            getOperator(buttonText);
            break;
        case R.id.bMultiply:
            buttonText = "*";
            ButtonMultiply = (Button) findViewById(R.id.bMultiply);
            ButtonMultiply.setText(buttonText);
            getOperator(buttonText);
            break;
        case R.id.bDivide:
            buttonText = "/";
            ButtonDivide = (Button) findViewById(R.id.bDivide);
            ButtonDivide.setText(buttonText);
            getOperator(buttonText);
            break;

        // Here's the equals button. When I click it it prints out "0.0", the value of total1, instead of adding the total below
        case R.id.bEqual:
            switch (theOperator) {
            case '+':
                total2 = total1 + displayValue;
                break;
            case '-':
                total2 = total1 - displayValue;
                break;
            case '*':
                total2 = total1 * displayValue;
                break;
            case '/':
                total2 = total1 / displayValue;
                break;
            }
            display.setText(Double.toString(total2));
            total1 = 0.0;
            break; 
        }                       
    }
}

Answer 1

我只看到一个位置，其中total1变量已被修改，并且其中添加了displayValue的值。 displayValue只在onCreate方法（每个活动生命周期只调用一次）中修改一次，editText1控件的内容加载total1控件（我们没有源代码）对）。

所以简而言之，我并不感到惊讶{{1}}没有被修改。这是检查应用程序的整个逻辑流程的问题。

Answer 2

您正尝试在get运算符方法中添加displayValue，但您尚未更改此值。在将其添加到total1之前，您应该从显示中削减此值。它应该是这样的：

public void getOperator(String btnText){
    theOperator = btnText.charAt(0);



    total1+=Double.parseDouble(display.getText().ToString());
    display.setText("");
}

如果您需要保存当前显示值，可以这样：

public void getOperator(String btnText){
    theOperator = btnText.charAt(0);


    displayValue = Double.parseDouble(display.getText().ToString());
    total1+=displayValue;
    display.setText("");
}

Android计算器中未使用变量

2 个答案: