在Eclipse中使用JavaScript实现字符串运算

使用Eclipse中的JavaScript引擎实现字符串表达式计算

在Eclipse中，通过JavaScript引擎轻松实现字符串表达式的运算。我们可以利用eval()函数来执行JavaScript代码，从而实现复杂的数学运算。

安卓计算器开发实例

一、依赖管理

在build.gradle中添加必要的依赖：

implementation 'io.apisense:rhino-android:1.1.1'

二、布局配置

在activity_main.xml中定义布局：

三、功能实现

在MainActivity.java中，通过JavaScript引擎实现计算器功能：

package com.example.cal;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class MainActivity extends AppCompatActivity {
    private Button btnlim, btn0, btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9, btnp, btnadd, btnsub, btnmul, btndiv, btnequ;
    private TextView in;
    private String s = "", result = "";
    ScriptEngine j = new ScriptEngineManager().getEngineByName("javascript");
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        in = (TextView) findViewById(R.id.input);
        btnlim = (Button) findViewById(R.id.buttoneliminate);
        btn0 = (Button) findViewById(R.id.button0);
        btn1 = (Button) findViewById(R.id.button1);
        btn2 = (Button) findViewById(R.id.button2);
        btn3 = (Button) findViewById(R.id.button3);
        btn4 = (Button) findViewById(R.id.button4);
        btn5 = (Button) findViewById(R.id.button5);
        btn6 = (Button) findViewById(R.id.button6);
        btn7 = (Button) findViewById(R.id.button7);
        btn8 = (Button) findViewById(R.id.button8);
        btn9 = (Button) findViewById(R.id.button9);
        btnp = (Button) findViewById(R.id.buttonpoint);
        btnadd = (Button) findViewById(R.id.buttonadd);
        btnsub = (Button) findViewById(R.id.buttonsub);
        btnmul = (Button) findViewById(R.id.buttonmul);
        btndiv = (Button) findViewById(R.id.buttondiv);
        btnequ = (Button) findViewById(R.id.buttonequal);
        btnlim.setOnClickListener(new mclick());
        btn0.setOnClickListener(new mclick());
        btn1.setOnClickListener(new mclick());
        btn2.setOnClickListener(new mclick());
        btn3.setOnClickListener(new mclick());
        btn4.setOnClickListener(new mclick());
        btn5.setOnClickListener(new mclick());
        btn6.setOnClickListener(new mclick());
        btn7.setOnClickListener(new mclick());
        btn8.setOnClickListener(new mclick());
        btn9.setOnClickListener(new mclick());
        btnp.setOnClickListener(new mclick());
        btnadd.setOnClickListener(new mclick());
        btnsub.setOnClickListener(new mclick());
        btnmul.setOnClickListener(new mclick());
        btndiv.setOnClickListener(new mclick());
        btnequ.setOnClickListener(new mclick());
    }
    class mclick implements OnClickListener {
        public void onClick(View v) {
            if (v == btnlim) {
                s = "";
            } else if (v == btnequ) {
                try {
                    String t = s;
                    result = j.eval(t).toString();
                    s += "=" + result;
                    in.setText(s);
                    s = result;
                } catch (ScriptException e) {
                    e.printStackTrace();
                }
            } else {
                switch (v.getId()) {
                    case R.id.button0:
                        s += "0";
                        break;
                    case R.id.button1:
                        s += "1";
                        break;
                    case R.id.button2:
                        s += "2";
                        break;
                    case R.id.button3:
                        s += "3";
                        break;
                    case R.id.button4:
                        s += "4";
                        break;
                    case R.id.button5:
                        s += "5";
                        break;
                    case R.id.button6:
                        s += "6";
                        break;
                    case R.id.button7:
                        s += "7";
                        break;
                    case R.id.button8:
                        s += "8";
                        break;
                    case R.id.button9:
                        s += "9";
                        break;
                    case R.id.buttonpoint:
                        s += ".";
                        break;
                    case R.id.buttonadd:
                        s += "+";
                        break;
                    case R.id.buttonsub:
                        s += "-";
                        break;
                    case R.id.buttonmul:
                        s += "*";
                        break;
                    case R.id.buttondiv:
                        s += "/";
                        break;
                }
                in.setText(s);
            }
        }
    }
}

通过以上代码，我们可以在Android Studio中轻松实现一个功能简单的计算器。用户可以通过点击数字和操作符来构建表达式，点击"="按钮即可查看计算结果。

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