java - 计算器中的等于按钮什么都不做(Android 开发者工具)

Question

我真的想不通，我是编程初学者，做了大约 2 个月。我为 Android 制作了计算器，但问题是等于按钮什么都不做。

设置不同的变量:

Button one,two,three,four,five,six,seven,eight,nine,zero,plus,minus,divide,multiply,dot,equals;
ImageButton clear;
TextView result;
String theresult;

除了等号之外的所有按钮都只是将各自的文本附加到变量结果。

这里是只有等号按钮的代码(创建只是为了测试，但失败了):

    equals = (Button) findViewById(R.id.equals);
    equals.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            String expression = String.valueOf(result);

            if(expression.contains("+")){
            String[] numbers = expression.split("\\+");
            String no1 = numbers[0];
            String no2 = numbers[1];

            Double numb1 = Double.valueOf(no1);
            Double numb2 = Double.valueOf(no2);
            Double added = numb1+numb2;

            theresult = String.valueOf(added);
            result.setText(theresult);


            }
        }
    });

我在这里使用了 if ，这样我就可以使用 else if 来使其他操作起作用。稍后我也会使用 Try-Catch block 。感谢您的宝贵时间!

MainActivity.java 完整代码

package org.example.calc;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.TextView;

public class MainActivity extends Activity {

Button one,two,three,four,five,six,seven,eight,nine,zero,plus,minus,divide,multiply,dot,equals;
ImageButton clear;
TextView result;
String theresult;




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

    result = (TextView) findViewById(R.id.result);

    one = (Button) findViewById(R.id.one);
    one.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("1");
        }
    });


    two = (Button) findViewById(R.id.two);
    two.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("2");
        }
    });

    three = (Button) findViewById(R.id.three);
    three.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("3");
        }
    });

    four = (Button) findViewById(R.id.four);
    four.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("4");
        }
    });

    five = (Button) findViewById(R.id.five);
    five.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("5");
        }
    });


    six = (Button) findViewById(R.id.six);
    six.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("6");
        }
    });


    seven = (Button) findViewById(R.id.seven);
    seven.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("7");
        }
    });

    eight = (Button) findViewById(R.id.eight);
    eight.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("8");
        }
    });

    nine = (Button) findViewById(R.id.nine);
    nine.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("9");
        }
    });


    zero = (Button) findViewById(R.id.zero);
    zero.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("0");
        }
    });

    dot = (Button) findViewById(R.id.dot);
    dot.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append(".");
        }
    });


    clear = (ImageButton) findViewById(R.id.clear);
    clear.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.setText("");
        }
    });


    plus = (Button) findViewById(R.id.plus);
    plus.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("+");
        }
    });

    minus = (Button) findViewById(R.id.minus);
    minus.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("-");
        }
    });

    divide = (Button) findViewById(R.id.divide);
    divide.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("/");
        }
    });


    multiply = (Button) findViewById(R.id.multiply);
    multiply.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            result.append("x");
        }
    });


    equals = (Button) findViewById(R.id.equals);
    equals.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            result.getText();
            String expression = String.valueOf(result);

            if(expression.contains("+")){
            String[] numbers = expression.split("\\+");
            String no1 = numbers[0];
            String no2 = numbers[1];

            Double numb1 = Double.valueOf(no1);
            Double numb2 = Double.valueOf(no2);
            Double added = numb1+numb2;

            theresult = String.valueOf(added);
            result.setText(theresult);


            }
        }
    });




}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

Answer 1

就这样做:

@Override
public void onClick(View v) {
    String expression = result.getText().toString();
    // Log.d("LOG", expression);

    if(expression.contains("+")){
        (...)

也许工作。无需使用 String.valueOf()