0xA1 Android开发之简易四则计算器

0x00 功能

基于Java的Android四则运算器，可以进行浮点数的四则运算

计算器

0x01 开发工具

Android Studio、雷电模拟器、Android手机

0x02 基本简介

总体使用网格布局（七行四列）使用了两个TextView和十八个按钮,其中TextVIew采用滚动设计（跑马灯）解决TextView文本过长的显示问题，支持浮点数的+ - * / 以及百分比运算

0x03 踩坑经历

1.布局,由于不熟练导致的布局频频受阻
2.按钮监听,逐个按钮监听工作量有点大，故采用Button数组批量绑定并且监听，但是此举必先定义Button
3.逻辑代码,为了APP有更友好的交互，逻辑代码方面实在浪费了n多时间

0x04 核心代码

activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.feng.learn3.MainActivity"

    >

    <GridLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:rowCount="7"
        android:columnCount="4"
        android:id="@+id/gridLayout"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">

        <TextView
            android:gravity="right"
            android:textColor="#292828"
            android:text="0"
            android:layout_width="match_parent"
            android:ellipsize="marquee"
            android:singleLine="true"
            android:marqueeRepeatLimit="marquee_forever"
            android:textSize="60sp"
            android:layout_height="@dimen/button_height"
            android:layout_columnSpan="4"
            android:layout_column="0"
            android:layout_row="1"
            android:id="@+id/textView"
            android:layout_below="@+id/gridLayout"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true" />
    
        <Button
            android:text="@string/clear"
            android:layout_column="0"
            android:layout_row="2"
            android:layout_columnSpan="1"
            android:layout_gravity="fill"
            android:layout_width="wrap_content"
            android:layout_height="@dimen/button_height"
            android:id="@+id/buttonC" />
                    
        <!--……以下省略-->
    </GridLayout>
</RelativeLayout>

MainActivity.java文件

package com.feng.learn3;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;
    
    public class MainActivity extends AppCompatActivity implements View.OnClickListener {
        //按钮0~9
        private Button buttonP;
        private Button button0;
        private Button button1;
        private Button button2;
        private Button button3;
        private Button button4;
        private Button button5;
        private Button button6;
        private Button button7;
        private Button button8;
        private Button button9;
        //按钮 + - * / =
        private Button buttonA;
        private Button buttonS;
        private Button buttonM;
        private Button buttonD;
        private Button buttonE;
        //按钮 CE C
        private Button buttonB;
        private Button buttonC;
        //百分号按钮
        private Button buttonPer;
        //TextView
        private TextView textView;
        private TextView hintTestView;
        //左右操作数
        private Double left = 0.0;
        private Double right = 0.0;
        //操作符
        private String operator = "#";
        //操作符选中标志
        private byte tag = 0;
    
        Button[] buttons = {buttonP,button0,button1,button2,button3,button4,button5,button6,button7,
                button8,button9,buttonA,buttonS,buttonM,buttonD,buttonE,buttonB,buttonC,buttonPer};
        Integer[] ids = {R.id.buttonP,R.id.button0,R.id.button1,R.id.button2,R.id.button3,R.id.button4,R.id.button5,
                R.id.button6,R.id.button7,R.id.button8,R.id.button9,R.id.buttonA,R.id.buttonS,
                R.id.buttonM,R.id.buttonD,R.id.buttonE,R.id.buttonB,R.id.buttonC,R.id.buttonPer};
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            //绑定Textiews
            textView = (TextView) findViewById(R.id.textView);
            hintTestView = (TextView) findViewById(R.id.textView1);
            textView.setSelected(true);
            hintTestView.setSelected(true);
            //绑定Buttons并监听之
            for (int i = 0; i < 19; i++){
                buttons[i] = (Button) findViewById(ids[i]);
                buttons[i].setOnClickListener(this);
            }
        }
    
        @Override
        public void onClick(View view) {
            //逻辑代码
            String op = (String) ((Button)view).getText();
            switch (op){
                case "0":
                case "1":
                case "2":
                case "3":
                case "4":
                case "5":
                case "6":
                case "7":
                case "8":
                case "9":
                    for (int i = 11; i < 17; i++){
                        buttons[i].setEnabled(true);
                    }
                    if (tag == 1){
                        tag = 0;
                        textView.setText("");
                    }
                    if (textView.getText().toString().startsWith("0") && !textView.getText().toString().startsWith("0.")){
                        textView.setText(op);
                    } else {
                        textView.setText(textView.getText().toString().concat(op));
                    }
                    break;
                case ".":
                    if (tag == 1){
                        tag = 0;
                        textView.setText("0.");
                    } else {
                        textView.setText(textView.getText().toString().concat(op));
                    }
                    buttons[0].setEnabled(false);//"."点按钮在每个操作数仅可使用一次
                    break;
                case "%":
                    Double temp = 0.0;
                    temp = temp.valueOf(textView.getText().toString());
                    temp /= 100;
                    textView.setText(temp.toString());
                    break;
                case "+":
                case "-":
                case "*":
                case "/":
                    setOperator(op);break;
                case "=":
                    setOperator(op);
                    textView.setText(left.toString());
                    hintTestView.setText("");
                    for (int i = 11; i < 17; i++){
                        buttons[i].setEnabled(false);
                    }
                    left = 0.0;
                    right = 0.0;
                    break;
                case "CE"://后退一位
                    textView.setText(textView.getText().subSequence(0,textView.getText().length()-1));
                    break;
                case "C"://清零
                    textView.setText("0");
                    hintTestView.setText("");
                    buttons[0].setEnabled(true);
                    for (int i = 11; i < 17; i++){
                        buttons[i].setEnabled(true);
                    }
                    left = 0.0;
                    right = 0.0;
                    tag = 0;
                    break;
            }
        }
    
        //选中对应操作符计算左右操作数结果
        public void setOperator(String op){
            if (tag == 1){
                //临时更换操作符
                hintTestView.setText(hintTestView.getText().subSequence(0,hintTestView.getText().length()-2) + op + " ");
            } else {
                if (hintTestView.getText().toString().equals("")){
                    hintTestView.setText(textView.getText() + " " + op + " ");
                } else {
                    hintTestView.setText(hintTestView.getText().toString() + textView.getText() +  " " + op + " ");
                }
                right = right.valueOf(textView.getText().toString());
                left = new Cal().cal(operator,left,right);
                textView.setText(left.toString());
                tag = 1;
            }
            buttons[0].setEnabled(true);
            operator = op;
        }
    
    }

Cal.java文件

package com.feng.learn3;

/**
 * Created by 枫 on 2019/2/10.
 */

public class Cal {
    public double cal (String op,double left,double right){
        double ans = 0.0;
        switch (op){
            case "+":ans = add(left,right);break;
            case "-":ans = sub(left, right);break;
            case "*":ans = mul(left, right);break;
            case "/":ans = div(left, right);break;
        }
        return ans;
    }

    public double add (double left,double right){
        return left + right;
    }

    public double sub (double left,double right){
        return left - right;
    }

    public double mul (double left,double right){
        return left * right;
    }

    public double div (double left,double right){
        if (right != 0){
            return left/right;
        } else {
            return 0;
        }
    }
}