java创建计算器

Question

我正在尝试在安卓 studio上构建一个计算器。我的问题是，为了从任一值中获得解决方案，用户必须按下“等于”按钮。我试图避免这种情况，并在TextView中显示实时计算（当两个数字与加法符号组合时，一旦调用第二个运算符，总和就会出现）。如果有人能给我提供一些很好的见解，我还不是一个经验丰富的安卓开发者。谢谢

public class MainActivity extends AppCompatActivity {

Button button0, button1, button2, button3, button4, button5, button6, button7, button8,
button9, buttonAdd, buttonSub, buttonMult, buttonDiv, buttonDec, buttonEqual, buttonAC;

TextView calculate;

boolean addition, subtraction, division, multiplication;

float first, second;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    button0 = (Button) findViewById(R.id.button_num0);
    button1 = (Button) findViewById(R.id.button_num1);
    button2 = (Button) findViewById(R.id.button_num2);
    button3 = (Button) findViewById(R.id.button_num3);
    button4 = (Button) findViewById(R.id.button_num4);
    button5 = (Button) findViewById(R.id.button_num5);
    button6 = (Button) findViewById(R.id.button_num6);
    button7 = (Button) findViewById(R.id.button_num7);
    button8 = (Button) findViewById(R.id.button_num8);
    button9 = (Button) findViewById(R.id.button_num9);
    buttonAdd = (Button) findViewById(R.id.button_add);
    buttonSub = (Button) findViewById(R.id.button_subtract);
    buttonDiv = (Button) findViewById(R.id.button_divide);
    buttonMult = (Button) findViewById(R.id.button_multiply);
    buttonDec = (Button) findViewById(R.id.button_decimal);
    buttonEqual = (Button) findViewById(R.id.button_equal);
    buttonAC = (Button) findViewById(R.id.button_clear);

    calculate = (TextView) findViewById(R.id.text_current);

    button0.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button0.getText().toString());
        }
    });
    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button1.getText().toString());
        }
    });
    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button2.getText().toString());
        }
    });
    button3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button3.getText().toString());
        }
    });
    button4.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button4.getText().toString());
        }
    });
    button5.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button5.getText().toString());
        }
    });
    button6.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button6.getText().toString());
        }
    });
    button7.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button7.getText().toString());
        }
    });
    button8.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button8.getText().toString());
        }
    });
    button9.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button9.getText().toString());
        }
    });
    buttonAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (calculate.getText().equals(null)) {
                calculate.setText("");
            }
            else {
                first = Float.parseFloat(calculate.getText() + "");
                calculate.setText(calculate.getText() + "+");
                addition = true;
                calculate.setText(null);
            }
        }
    });
    buttonDec.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (calculate.getText().equals(null)) {
                calculate.setText("");
            }
            else {
                calculate.setText(calculate.getText() + ".");
            }
        }
    });
    buttonMult.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (calculate.getText().equals(null)) {
                calculate.setText("");
            }
            else {
                first = Float.parseFloat(calculate.getText() + "");
                calculate.setText(calculate.getText() + "*");
                multiplication = true;
                calculate.setText(null);
            }
        }
    });
    buttonSub.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (calculate.getText().equals(null)) {
                calculate.setText("");
            }
            else {
                first = Float.parseFloat(calculate.getText() + "");
                calculate.setText(calculate.getText() + "-");
                subtraction = true;
                calculate.setText(null);
            }
        }
    });
    buttonDiv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (calculate.getText().equals(null)) {
                calculate.setText("");
            }
            else {
                first = Float.parseFloat(calculate.getText() + "");
                calculate.setText(calculate.getText() + "/");
                division = true;
                calculate.setText(null);
            }
        }
    });
    buttonEqual.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            second = Float.parseFloat(calculate.getText() + "");

            if (addition ==  true) {
                calculate.setText(first + second + "");
                addition = false;
            }
            if (subtraction ==  true) {
                calculate.setText(first - second + "");
                subtraction = false;
            }
            if (multiplication ==  true) {
                calculate.setText(first * second + "");
                multiplication = false;
            }
            if (division ==  true) {
                calculate.setText(first / second + "");
                division = false;
            }
        }
    });
}
}

Answer 1

试着先建立逻辑，总是问自己，能做什么，怎么做

在工程或学校里，你可能听过这样的话：

1. 运算符( +, - , *, / )
2. 操作数( 0 to 9 )

What should happen when operands ( Numbers ) are pressed ?

首先将布尔变量operandAdded设为false。比如：

operandAdded = false;

无论何时在每个数字事件中按下，都要使其成为现实

What should happen when operators ( +, -, *, / ) are pressed ?

首先将布尔变量operatorAdded设为false。比如：

operatorAdded = false;

无论何时在每个操作员按下事件中，都要使其为真

现在，每当按下数字时，调用一个函数，该函数将检查2个布尔值：

if (operatorAdded && operandAdded) {
     // this is where you will perform maths
     // this is where you show it in the textView
     // this is where make both false again
}

希望能有帮助

Answer 2

你有很多重复。 因此，当您要为任何按钮更改某些内容时，您必须为其他按钮进行修改。尽量减少代码行数，方法是为每个按钮添加整个侦听器。通过这种方式，您还将拥有一个cleaneronCreate方法

private void addListenerTo(int buttonId) {
    final Button button = (Button) findViewById(buttonId);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculate.setText(calculate.getText() + button.getText().toString());
        }
    });
}

然后，您可以像这样轻松添加所有按钮：

addListenerTo(R.id.button_num0);
addListenerTo(R.id.button_num1);
addListenerTo(R.id.button_num2);
addListenerTo(R.id.button_num3);
addListenerTo(R.id.button_num4);
addListenerTo(R.id.button_num5);
addListenerTo(R.id.button_num6);
addListenerTo(R.id.button_num7);
addListenerTo(R.id.button_num8);
addListenerTo(R.id.button_num9);

您还应该能够使用运算符按钮执行类似的操作。 如果你需要帮忙，我会帮你的。 通过这样做，您的代码将更易于阅读，这对我们是一个很大的帮助

Answer 3

您可以使用Edittext而不是textview，并在其上实现文本更改侦听器。 因此，每当文本发生更改时，您都可以获得更改并进行实时计算

您可以使用以下URL作为参考：-

https://developer.android.com/reference/android/text/TextWatcher

android on Text Change Listener