Android 科学计算器代码

这是一个简单的 Android 科学计算器代码示例：

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 implements View.OnClickListener {

    EditText editText;
    Button button0, button1, button2, button3, button4, button5, button6, button7, button8, button9;
    Button buttonAdd, buttonSub, buttonMul, buttonDiv, buttonEqual, buttonClear;

    float value1, value2;
    boolean add, sub, mul, div;

    @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);
        buttonSub = findViewById(R.id.buttonSub);
        buttonMul = findViewById(R.id.buttonMul);
        buttonDiv = findViewById(R.id.buttonDiv);
        buttonEqual = findViewById(R.id.buttonEqual);
        buttonClear = findViewById(R.id.buttonClear);

        button0.setOnClickListener(this);
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
        button4.setOnClickListener(this);
        button5.setOnClickListener(this);
        button6.setOnClickListener(this);
        button7.setOnClickListener(this);
        button8.setOnClickListener(this);
        button9.setOnClickListener(this);
        buttonAdd.setOnClickListener(this);
        buttonSub.setOnClickListener(this);
        buttonMul.setOnClickListener(this);
        buttonDiv.setOnClickListener(this);
        buttonEqual.setOnClickListener(this);
        buttonClear.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button0:
                editText.setText(editText.getText() + "0");
                break;
            case R.id.button1:
                editText.setText(editText.getText() + "1");
                break;
            case R.id.button2:
                editText.setText(editText.getText() + "2");
                break;
            case R.id.button3:
                editText.setText(editText.getText() + "3");
                break;
            case R.id.button4:
                editText.setText(editText.getText() + "4");
                break;
            case R.id.button5:
                editText.setText(editText.getText() + "5");
                break;
            case R.id.button6:
                editText.setText(editText.getText() + "6");
                break;
            case R.id.button7:
                editText.setText(editText.getText() + "7");
                break;
            case R.id.button8:
                editText.setText(editText.getText() + "8");
                break;
            case R.id.button9:
                editText.setText(editText.getText() + "9");
                break;
            case R.id.buttonAdd:
                if (editText == null) {
                    editText.setText("");
                } else {
                    value1 = Float.parseFloat(editText.getText() + "");
                    add = true;
                    editText.setText(null);
                }
                break;
            case R.id.buttonSub:
                if (editText == null) {
                    editText.setText("");
                } else {
                    value1 = Float.parseFloat(editText.getText() + "");
                    sub = true;
                    editText.setText(null);
                }
                break;
            case R.id.buttonMul:
                if (editText == null) {
                    editText.setText("");
                } else {
                    value1 = Float.parseFloat(editText.getText() + "");
                    mul = true;
                    editText.setText(null);
                }
                break;
            case R.id.buttonDiv:
                if (editText == null) {
                    editText.setText("");
                } else {
                    value1 = Float.parseFloat(editText.getText() + "");
                    div = true;
                    editText.setText(null);
                }
                break;
            case R.id.buttonEqual:
                value2 = Float.parseFloat(editText.getText() + "");

                if (add) {
                    editText.setText(value1 + value2 + "");
                    add = false;
                }

                if (sub) {
                    editText.setText(value1 - value2 + "");
                    sub = false;
                }

                if (mul) {
                    editText.setText(value1 * value2 + "");
                    mul = false;
                }

                if (div) {
                    editText.setText(value1 / value2 + "");
                    div = false;
                }
                break;

            case R.id.buttonClear:
                editText.setText("");
                break;
        }
    }
}

代码中使用了 `EditText` 控件来显示计算结果，并使用了多个 `Button` 控件作为计算器的按钮。计算器支持加、减、乘、除四则运算，以及清除和等号操作。