Android开发之简易计算器

使用GridLayout对计算器按键进行布局，大致代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="5dp"
    tools:context=".MainActivity">

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

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="计算器"
                android:gravity="center"
                android:textColor="@color/colorPrimaryDark"
                android:textSize="30sp"/>
            <TextView
                android:id="@+id/tv_result"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="#FFFF"
                android:text="0"
                android:textSize="25sp"
                android:lines="7"
                android:gravity="bottom|right"/>
            <GridLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:columnCount="4"
                android:rowCount="5">
                <Button
                    android:id="@+id/btn_cancel"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="C"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_percentage"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="%"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <ImageButton
                    android:id="@+id/btn_backspace"
                    android:width="0dp"
                    android:layout_height="75dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:scaleType="centerInside"
                    android:src="@drawable/backspace"
                    />
                <Button
                    android:id="@+id/btn_divider"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="/"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_seven"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="7"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_eight"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="8"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_nine"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="9"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_multiply"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="*"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_four"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="4"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_five"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="5"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_six"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="6"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_minus"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="-"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_one"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="1"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_two"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="2"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_three"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="3"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_plus"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="+"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_doublezero"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="00"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_zero"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="0"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_point"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="."
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
                <Button
                    android:id="@+id/btn_equal"
                    android:width="0dp"
                    android:height="@dimen/button_height_size"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="="
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="@dimen/button_font_size"/>
            </GridLayout>
        </LinearLayout>
    </ScrollView>

</LinearLayout>

主要逻辑代码如下：

package com.njyd.calculatoractivity;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_result;
    //第一个操作数
    private String firstNum = "";
    //运算符
    private String operator = "";
    //第二个操作数
    private String secondNum = "";
    //当前的计算结果
    private String result = "";
    //显示的文本内容
    private String showText = "";

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

    private void initView() {
        //获取布局文件中的组件
        tv_result = findViewById(R.id.tv_result);
        findViewById(R.id.btn_cancel).setOnClickListener(this);
        findViewById(R.id.btn_percentage).setOnClickListener(this);
        findViewById(R.id.btn_backspace).setOnClickListener(this);
        findViewById(R.id.btn_divider).setOnClickListener(this);
        findViewById(R.id.btn_seven).setOnClickListener(this);
        findViewById(R.id.btn_eight).setOnClickListener(this);
        findViewById(R.id.btn_nine).setOnClickListener(this);
        findViewById(R.id.btn_multiply).setOnClickListener(this);
        findViewById(R.id.btn_four).setOnClickListener(this);
        findViewById(R.id.btn_five).setOnClickListener(this);
        findViewById(R.id.btn_six).setOnClickListener(this);
        findViewById(R.id.btn_minus).setOnClickListener(this);
        findViewById(R.id.btn_one).setOnClickListener(this);
        findViewById(R.id.btn_two).setOnClickListener(this);
        findViewById(R.id.btn_three).setOnClickListener(this);
        findViewById(R.id.btn_plus).setOnClickListener(this);
        findViewById(R.id.btn_doublezero).setOnClickListener(this);
        findViewById(R.id.btn_zero).setOnClickListener(this);
        findViewById(R.id.btn_point).setOnClickListener(this);
        findViewById(R.id.btn_equal).setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        String inputText;
            if (v.getId() == R.id.btn_backspace){
                inputText = "X";
            }else{
                inputText = ((TextView) v).getText().toString();
            }
        switch (v.getId()) {
            //点击了退格按钮
            case R.id.btn_backspace:
                if (operator.equals("")) {
                    firstNum = String.valueOf((int)(Double.parseDouble(firstNum) / 10));
                    updateText(firstNum);
                }else if(secondNum ==""){
                    operator = "";
                    updateText(firstNum + operator + secondNum);
                }else {
                    secondNum = String.valueOf((int)(Double.parseDouble(firstNum) / 10));
                    updateText(firstNum + operator + secondNum);
                }
                break;
            //点击了清除按钮
            case R.id.btn_cancel:
                clear();
                break;
            //点击了加减乘除
            case R.id.btn_plus:
            case R.id.btn_minus:
            case R.id.btn_multiply:
            case R.id.btn_divider:
                operator = inputText;//运算符
                updateText(showText + operator);
                break;
            //点击了等号按钮
            case R.id.btn_equal:
                //加减乘除四则运算
                double calculate_result = calculate();
                updateOperate(String.valueOf(calculate_result));
                updateText(showText + "=" + result);
                break;
            //点击了百分号按钮
            case R.id.btn_percentage:
                if (operator.equals("")) {
                    firstNum = String.valueOf(Double.parseDouble(firstNum) * 0.01);
                    updateText(firstNum);
                } else {
                    //有运算符，则继续拼接第二个操作数
                    secondNum = String.valueOf(Double.parseDouble(secondNum) * 0.01);
                    updateText(firstNum + operator + secondNum);
                }
                break;

            //点击了其他按钮
            default:
                //上次的运算结果已经出来了
                if (result.length() > 0 && operator.equals("")){
                    clear();
                }
                //无运算符，则继续拼接第一个操作数
                if (operator.equals("")) {
                    firstNum = firstNum + inputText;
                } else {
                    //有运算符，则继续拼接第二个操作数
                    secondNum = secondNum + inputText;
                }
                //整数前不需要0
                if (showText.equals("0") && !inputText.equals(".")){
                    updateText(inputText);
                }else {
                    updateText(showText + inputText);
                }
                break;

        }

    }

    private double calculate() {
        switch (operator){
            case "+":
                return Double.parseDouble(firstNum) + Double.parseDouble(secondNum);
            case "-":
                return Double.parseDouble(firstNum) - Double.parseDouble(secondNum);
            case "*":
                return Double.parseDouble(firstNum) * Double.parseDouble(secondNum);
            case "/":
                return Double.parseDouble(firstNum) / Double.parseDouble(secondNum);
        }
        return 0;
    }

    private void clear() {
        updateOperate("");
        updateText("");
    }
    //刷新运算结果
    private void updateOperate(String new_result){
        result = new_result;
        firstNum = result;
        secondNum = "";
        operator = "";
    }
    //刷新文本显示
    private void updateText(String text){
        showText = text;
        tv_result.setText(showText);
    }
}

运行效果如下：

clear() {
updateOperate(“”);
updateText(“”);
}
//刷新运算结果
private void updateOperate(String new_result){
result = new_result;
firstNum = result;
secondNum = “”;
operator = “”;
}
//刷新文本显示
private void updateText(String text){
showText = text;
tv_result.setText(showText);
}
}

运行效果如下：
![在这里插入图片描述](https://img-blog.csdnimg.cn/c1849ce38aec4088acc92d2c83579118.png#pic_center)