帮我用androidStudio写一个计算器代码

好的，下面是一个简单的计算器代码，你可以在Android Studio中创建一个新项目并将其复制到MainActivity.java文件中：

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText resultEditText;
    private Button[] numberButtons = new Button[10];
    private Button[] operatorButtons = new Button[5];
    private Button clearButton, equalButton;
    private double num1 = 0, num2 = 0;
    private String operator = "";
    private boolean isOperatorPressed = false;

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

        resultEditText = findViewById(R.id.resultEditText);
        clearButton = findViewById(R.id.clearButton);
        equalButton = findViewById(R.id.equalButton);

        for (int i = 0; i < numberButtons.length; i++) {
            numberButtons[i] = findViewById(getResources().getIdentifier("button" + i, "id", getPackageName()));
            numberButtons[i].setOnClickListener(this);
        }

        operatorButtons[0] = findViewById(R.id.additionButton);
        operatorButtons[1] = findViewById(R.id.subtractionButton);
        operatorButtons[2] = findViewById(R.id.multiplicationButton);
        operatorButtons[3] = findViewById(R.id.divisionButton);
        operatorButtons[4] = findViewById(R.id.decimalButton);

        for (int i = 0; i < operatorButtons.length; i++) {
            operatorButtons[i].setOnClickListener(this);
        }

        clearButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                resultEditText.setText("");
                num1 = 0;
                num2 = 0;
                isOperatorPressed = false;
            }
        });

        equalButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                isOperatorPressed = false;
                num2 = Double.parseDouble(resultEditText.getText().toString());

                switch (operator) {
                    case "+":
                        resultEditText.setText(String.valueOf(num1 + num2));
                        break;
                    case "-":
                        resultEditText.setText(String.valueOf(num1 - num2));
                        break;
                    case "*":
                        resultEditText.setText(String.valueOf(num1 * num2));
                        break;
                    case "/":
                        if (num2 == 0) {
                            resultEditText.setText("Error");
                        } else {
                            resultEditText.setText(String.valueOf(num1 / num2));
                        }
                        break;
                }
            }
        });
    }

    @Override
    public void onClick(View v) {
        if (isOperatorPressed) {
            resultEditText.setText("");
        }

        isOperatorPressed = false;

        switch (v.getId()) {
            case R.id.button0:
                resultEditText.append("0");
                break;
            case R.id.button1:
                resultEditText.append("1");
                break;
            case R.id.button2:
                resultEditText.append("2");
                break;
            case R.id.button3:
                resultEditText.append("3");
                break;
            case R.id.button4:
                resultEditText.append("4");
                break;
            case R.id.button5:
                resultEditText.append("5");
                break;
            case R.id.button6:
                resultEditText.append("6");
                break;
            case R.id.button7:
                resultEditText.append("7");
                break;
            case R.id.button8:
                resultEditText.append("8");
                break;
            case R.id.button9:
                resultEditText.append("9");
                break;
            case R.id.additionButton:
                operator = "+";
                num1 = Double.parseDouble(resultEditText.getText().toString());
                isOperatorPressed = true;
                break;
            case R.id.subtractionButton:
                operator = "-";
                num1 = Double.parseDouble(resultEditText.getText().toString());
                isOperatorPressed = true;
                break;
            case R.id.multiplicationButton:
                operator = "*";
                num1 = Double.parseDouble(resultEditText.getText().toString());
                isOperatorPressed = true;
                break;
            case R.id.divisionButton:
                operator = "/";
                num1 = Double.parseDouble(resultEditText.getText().toString());
                isOperatorPressed = true;
                break;
            case R.id.decimalButton:
                if (!resultEditText.getText().toString().contains(".")) {
                    resultEditText.append(".");
                }
                break;
        }
    }
}

此代码中，我们首先在onCreate方法中初始化UI元素，例如EditText和按钮。然后，我们为数字按钮和运算符按钮设置监听器，并设置相应的操作。最后，我们处理清除和等于按钮的点击事件，并执行相应的计算逻辑。