android student写一个计算器

好的，以下是一个简单的 Android 计算器示例代码：

1. 创建 XML 布局文件 activity_main.xml，添加以下代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/tv_result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:background="#EFEFEF"
        android:gravity="end"
        android:maxLines="1"
        android:padding="16dp"
        android:textSize="32sp" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="1"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="2"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="3"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_add"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="+"
            android:textSize="24sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="4"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_5"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="5"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_6"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="6"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_subtract"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="-"
            android:textSize="24sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_7"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="7"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_8"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="8"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_9"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="9"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_multiply"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="*"
            android:textSize="24sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_clear"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="C"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_0"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="0"
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_equals"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="="
            android:textSize="24sp" />

        <Button
            android:id="@+id/btn_divide"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="/"
            android:textSize="24sp" />

    </LinearLayout>

</LinearLayout>

2. 在 MainActivity.java 中添加以下代码：

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    private TextView tvResult;

    private String currentNumber = "";
    private String lastOperation = "";
    private String operand1 = "";
    private String operand2 = "";

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

        tvResult = findViewById(R.id.tv_result);

        Button btn0 = findViewById(R.id.btn_0);
        Button btn1 = findViewById(R.id.btn_1);
        Button btn2 = findViewById(R.id.btn_2);
        Button btn3 = findViewById(R.id.btn_3);
        Button btn4 = findViewById(R.id.btn_4);
        Button btn5 = findViewById(R.id.btn_5);
        Button btn6 = findViewById(R.id.btn_6);
        Button btn7 = findViewById(R.id.btn_7);
        Button btn8 = findViewById(R.id.btn_8);
        Button btn9 = findViewById(R.id.btn_9);
        Button btnClear = findViewById(R.id.btn_clear);
        Button btnAdd = findViewById(R.id.btn_add);
        Button btnSubtract = findViewById(R.id.btn_subtract);
        Button btnMultiply = findViewById(R.id.btn_multiply);
        Button btnDivide = findViewById(R.id.btn_divide);
        Button btnEquals = findViewById(R.id.btn_equals);

        btn0.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("0");
            }
        });

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("1");
            }
        });

        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("2");
            }
        });

        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("3");
            }
        });

        btn4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("4");
            }
        });

        btn5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("5");
            }
        });

        btn6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("6");
            }
        });

        btn7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("7");
            }
        });

        btn8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("8");
            }
        });

        btn9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleNumberClick("9");
            }
        });

        btnClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                clear();
            }
        });

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleOperationClick("+");
            }
        });

        btnSubtract.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleOperationClick("-");
            }
        });

        btnMultiply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleOperationClick("*");
            }
        });

        btnDivide.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleOperationClick("/");
            }
        });

        btnEquals.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                handleEqualsClick();
            }
        });
    }

    private void handleNumberClick(String number) {
        currentNumber += number;
        tvResult.setText(currentNumber);
    }

    private void handleOperationClick(String operation) {
        if (!currentNumber.isEmpty()) {
            operand1 = currentNumber;
            currentNumber = "";
            lastOperation = operation;
        }
    }

    private void handleEqualsClick() {
        if (!currentNumber.isEmpty()) {
            operand2 = currentNumber;
            currentNumber = "";
        }

        if (!operand1.isEmpty() && !operand2.isEmpty()) {
            double num1 = Double.parseDouble(operand1);
            double num2 = Double.parseDouble(operand2);
            double result = 0;

            switch (lastOperation) {
                case "+":
                    result = num1 + num2;
                    break;
                case "-":
                    result = num1 - num2;
                    break;
                case "*":
                    result = num1 * num2;
                    break;
                case "/":
                    result = num1 / num2;
                    break;
            }

            operand1 = String.valueOf(result);
            operand2 = "";
            lastOperation = "";
            currentNumber = operand1;
            tvResult.setText(currentNumber);
        }
    }

    private void clear() {
        currentNumber = "";
        operand1 = "";
        operand2 = "";
        lastOperation = "";
        tvResult.setText("");
    }
}

这个计算器支持加、减、乘、除四种基本运算，以及清空和等于操作。希望这能帮到你！