android的简单计算器代码

下面是一个使用 Java 编写的 Android 简单计算器代码示例：

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView tvResult;
    private String currentNumber;
    private String nextNumber;
    private int currentOperator;

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

        currentNumber = "";
        nextNumber = "";
        currentOperator = -1;

        tvResult = findViewById(R.id.tvResult);

        Button btn0 = findViewById(R.id.btn0);
        Button btn1 = findViewById(R.id.btn1);
        Button btn2 = findViewById(R.id.btn2);
        Button btn3 = findViewById(R.id.btn3);
        Button btn4 = findViewById(R.id.btn4);
        Button btn5 = findViewById(R.id.btn5);
        Button btn6 = findViewById(R.id.btn6);
        Button btn7 = findViewById(R.id.btn7);
        Button btn8 = findViewById(R.id.btn8);
        Button btn9 = findViewById(R.id.btn9);
        Button btnClear = findViewById(R.id.btnClear);
        Button btnPlus = findViewById(R.id.btnPlus);
        Button btnMinus = findViewById(R.id.btnMinus);
        Button btnMultiply = findViewById(R.id.btnMultiply);
        Button btnDivide = findViewById(R.id.btnDivide);
        Button btnEqual = findViewById(R.id.btnEqual);

        btn0.setOnClickListener(this);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
        btn3.setOnClickListener(this);
        btn4.setOnClickListener(this);
        btn5.setOnClickListener(this);
        btn6.setOnClickListener(this);
        btn7.setOnClickListener(this);
        btn8.setOnClickListener(this);
        btn9.setOnClickListener(this);
        btnClear.setOnClickListener(this);
        btnPlus.setOnClickListener(this);
        btnMinus.setOnClickListener(this);
        btnMultiply.setOnClickListener(this);
        btnDivide.setOnClickListener(this);
        btnEqual.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.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.btnClear:
                currentNumber = "";
                nextNumber = "";
                currentOperator = -1;
                tvResult.setText("0");
                break;
            case R.id.btnPlus:
                if (currentNumber.length() > 0) {
                    nextNumber = currentNumber;
                    currentNumber = "";
                    currentOperator = 1;
                    tvResult.setText("+");
                }
                break;
            case R.id.btnMinus:
                if (currentNumber.length() > 0) {
                    nextNumber = currentNumber;
                    currentNumber = "";
                    currentOperator = 2;
                    tvResult.setText("-");
                }
                break;
            case R.id.btnMultiply:
                if (currentNumber.length() > 0) {
                    nextNumber = currentNumber;
                    currentNumber = "";
                    currentOperator = 3;
                    tvResult.setText("*");
                }
                break;
            case R.id.btnDivide:
                if (currentNumber.length() > 0) {
                    nextNumber = currentNumber;
                    currentNumber = "";
                    currentOperator = 4;
                    tvResult.setText("/");
                }
                break;
            case R.id.btnEqual:
                if (nextNumber.length() > 0 && currentNumber.length() > 0) {
                    float result = 0;
                    float num1 = Float.parseFloat(nextNumber);
                    float num2 = Float.parseFloat(currentNumber);
                    switch (currentOperator) {
                        case 1:
                            result = num1 + num2;
                            break;
                        case 2:
                            result = num1 - num2;
                            break;
                        case 3:
                            result = num1 * num2;
                            break;
                        case 4:
                            result = num1 / num2;
                            break;
                    }
                    tvResult.setText(String.valueOf(result));
                    currentNumber = String.valueOf(result);
                    nextNumber = "";
                    currentOperator = -1;
                }
                break;
        }
    }
}

这个简单计算器支持加减乘除四则运算，使用了一个 TextView 控件来显示当前输入的数字和运算结果。它由多个 Button 控件组成，每个按钮绑定了一个点击事件，根据用户的输入，动态更新 TextView 中的文本。在用户点击等于号时，会将两个数字和运算符传递给一个算法，计算出结果并显示到 TextView 中。