android studio简易计算器的代码实现,功能包括加，减，乘，除，平方根，倒数

下面是Android Studio简易计算器的代码实现：

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private EditText editText;
    private Button button0, button1, button2, button3, button4, button5,
            button6, button7, button8, button9, buttonAdd, buttonMinus,
            buttonDivide, buttonMultiply, buttonClear, buttonEqual, buttonSquareRoot, buttonInverse, buttonDot;
    private double num1 = 0, num2 = 0;
    private String operator = "";

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

        editText = findViewById(R.id.editText);
        button0 = findViewById(R.id.button0);
        button1 = findViewById(R.id.button1);
        button2 = findViewById(R.id.button2);
        button3 = findViewById(R.id.button3);
        button4 = findViewById(R.id.button4);
        button5 = findViewById(R.id.button5);
        button6 = findViewById(R.id.button6);
        button7 = findViewById(R.id.button7);
        button8 = findViewById(R.id.button8);
        button9 = findViewById(R.id.button9);
        buttonAdd = findViewById(R.id.buttonAdd);
        buttonMinus = findViewById(R.id.buttonMinus);
        buttonDivide = findViewById(R.id.buttonDivide);
        buttonMultiply = findViewById(R.id.buttonMultiply);
        buttonClear = findViewById(R.id.buttonClear);
        buttonEqual = findViewById(R.id.buttonEqual);
        buttonSquareRoot = findViewById(R.id.buttonSquareRoot);
        buttonInverse = findViewById(R.id.buttonInverse);
        buttonDot = findViewById(R.id.buttonDot);

        button0.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "0");
            }
        });

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "1");
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "2");
            }
        });

        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "3");
            }
        });

        button4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "4");
            }
        });

        button5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "5");
            }
        });

        button6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "6");
            }
        });

        button7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "7");
            }
        });

        button8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "8");
            }
        });

        button9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + "9");
            }
        });

        buttonAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                operator = "+";
                num1 = Double.parseDouble(editText.getText().toString());
                editText.setText("");
            }
        });

        buttonMinus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                operator = "-";
                num1 = Double.parseDouble(editText.getText().toString());
                editText.setText("");
            }
        });

        buttonDivide.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                operator = "/";
                num1 = Double.parseDouble(editText.getText().toString());
                editText.setText("");
            }
        });

        buttonMultiply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                operator = "*";
                num1 = Double.parseDouble(editText.getText().toString());
                editText.setText("");
            }
        });

        buttonClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText("");
            }
        });

        buttonEqual.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                num2 = Double.parseDouble(editText.getText().toString());
                if (operator.equals("+")) {
                    double result = num1 + num2;
                    editText.setText(String.valueOf(result));
                } else if (operator.equals("-")) {
                    double result = num1 - num2;
                    editText.setText(String.valueOf(result));
                } else if (operator.equals("/")) {
                    double result = num1 / num2;
                    editText.setText(String.valueOf(result));
                } else if (operator.equals("*")) {
                    double result = num1 * num2;
                    editText.setText(String.valueOf(result));
                }
            }
        });

        buttonSquareRoot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                num1 = Double.parseDouble(editText.getText().toString());
                double result = Math.sqrt(num1);
                editText.setText(String.valueOf(result));
            }
        });

        buttonInverse.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                num1 = Double.parseDouble(editText.getText().toString());
                double result = 1 / num1;
                editText.setText(String.valueOf(result));
            }
        });

        buttonDot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                editText.setText(editText.getText() + ".");
            }
        });
    }
}

在这个代码中，我们设置了一个`operator`变量来存储操作符，并在每次点击加减乘除按钮时将第一个数字存储在`num1`变量中，清空文本框中的文本。然后，当点击等号按钮时，我们将第二个数字存储在`num2`变量中，执行所需的操作并将答案显示在文本框中。

对于“平方根”和“倒数”按钮，我们只需从文本框中获取第一个数字，并执行所需的操作即可。