写一个完善的android计算器代码

下面是一个完善的Android计算器代码，实现简单的加、减、乘、除功能，以及清除和删除功能：

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

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tvResult;
    private String currentNumber = "";
    private String lastOperation = "";
    private double result = 0;

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

        tvResult = findViewById(R.id.tvResult);

        findViewById(R.id.btn0).setOnClickListener(this);
        findViewById(R.id.btn1).setOnClickListener(this);
        findViewById(R.id.btn2).setOnClickListener(this);
        findViewById(R.id.btn3).setOnClickListener(this);
        findViewById(R.id.btn4).setOnClickListener(this);
        findViewById(R.id.btn5).setOnClickListener(this);
        findViewById(R.id.btn6).setOnClickListener(this);
        findViewById(R.id.btn7).setOnClickListener(this);
        findViewById(R.id.btn8).setOnClickListener(this);
        findViewById(R.id.btn9).setOnClickListener(this);
        findViewById(R.id.btnAdd).setOnClickListener(this);
        findViewById(R.id.btnSubtract).setOnClickListener(this);
        findViewById(R.id.btnMultiply).setOnClickListener(this);
        findViewById(R.id.btnDivide).setOnClickListener(this);
        findViewById(R.id.btnClear).setOnClickListener(this);
        findViewById(R.id.btnDelete).setOnClickListener(this);
        findViewById(R.id.btnEqual).setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn0:
                currentNumber += "0";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn1:
                currentNumber += "1";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn2:
                currentNumber += "2";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn3:
                currentNumber += "3";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn4:
                currentNumber += "4";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn5:
                currentNumber += "5";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn6:
                currentNumber += "6";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn7:
                currentNumber += "7";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn8:
                currentNumber += "8";
                tvResult.setText(currentNumber);
                break;
            case R.id.btn9:
                currentNumber += "9";
                tvResult.setText(currentNumber);
                break;
            case R.id.btnAdd:
                performOperation();
                lastOperation = "+";
                break;
            case R.id.btnSubtract:
                performOperation();
                lastOperation = "-";
                break;
            case R.id.btnMultiply:
                performOperation();
                lastOperation = "*";
                break;
            case R.id.btnDivide:
                performOperation();
                lastOperation = "/";
                break;
            case R.id.btnClear:
                clear();
                break;
            case R.id.btnDelete:
                delete();
                break;
            case R.id.btnEqual:
                calculate();
                break;
        }
    }

    private void performOperation() {
        if (!currentNumber.isEmpty()) {
            double number = Double.parseDouble(currentNumber);
            if (result == 0) {
                result = number;
            } else {
                switch (lastOperation) {
                    case "+":
                        result += number;
                        break;
                    case "-":
                        result -= number;
                        break;
                    case "*":
                        result *= number;
                        break;
                    case "/":
                        result /= number;
                        break;
                }
            }
            currentNumber = "";
        }
    }

    private void calculate() {
        if (!currentNumber.isEmpty()) {
            performOperation();
        }
        tvResult.setText(String.valueOf(result));
        result = 0;
        lastOperation = "";
    }

    private void clear() {
        currentNumber = "";
        result = 0;
        lastOperation = "";
        tvResult.setText("");
    }

    private void delete() {
        if (!currentNumber.isEmpty()) {
            currentNumber = currentNumber.substring(0, currentNumber.length() - 1);
            tvResult.setText(currentNumber);
        }
    }
}

在xml中，我们可以使用如下代码布局：

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/tvResult"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:padding="16dp"
        android:background="@color/colorPrimaryDark"
        android:textColor="@android:color/white"
        android:gravity="right"/>

    <GridLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:rowCount="5"
        android:columnCount="4"
        android:padding="8dp">

        <Button
            android:id="@+id/btnClear"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="C"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnDelete"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="DEL"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnDivide"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="/"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnMultiply"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="×"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn7"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="7"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn8"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="8"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn9"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="9"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnSubtract"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="-"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="4"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn5"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="5"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn6"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="6"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnAdd"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="+"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="1"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="2"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btn3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="3"
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnEqual"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="="
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="2"
            android:layout_gravity="fill"/>
        
        <Button
            android:id="@+id/btn0"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="0"
            android:textSize="24sp"
            android:layout_columnWeight="2"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>

        <Button
            android:id="@+id/btnDecimal"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="."
            android:textSize="24sp"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:layout_gravity="fill"/>
    </GridLayout>
</LinearLayout>

这里使用了GridLayout来实现按钮的布局，代码中使用了字符串转换成数字的方法实现计算功能。