[Basics of Android development] Calculator logic layer code supplement

I. Introduction

• Description: Regarding the blog published on June 12th [Basics of Android Development] SQLite development to replicate address books, notepads, and computers , a fan asked me if the last calculator assignment has logic layer code. I will give it here. Provide specific code.
• Difficulty: Beginner
• Effect
  

2. Design

1. Case

For beginners or friends who are not good at algorithms, I think it is necessary to take a look at such a calculation method first.
It seems to be called function nesting method (I forgot the professional term, if you know it, you can tell everyone in the comment area)

	public static void main(String[] args) {
    
    
		System.out.print("输入一个数，计算1~n的数和：");
		Scanner input = new Scanner(System.in);
		int max = input.nextInt();
		System.out.print("结果：" + add(0, 1, max));
	}

	private static int add(int S, int min, int max) {
    
    
		if(min <= max) {
    
    
			S += min;
			return add(S, ++min, max);
		}
		return S;
	}

2. Algorithm design

public class alg {
    
    

    public static double parse(String formula) {
    
    

        int temp = formula.indexOf("+");
        if (temp != -1) {
    
    
            return parse(formula.substring(0, temp)) + parse(formula.substring(temp + 1));
        }

        temp = formula.lastIndexOf("-");
        if (temp != -1) {
    
    
            return parse(formula.substring(0, temp)) - parse(formula.substring(temp + 1));
        }

        temp = formula.indexOf("*");
        if (temp != -1) {
    
    
            return parse(formula.substring(0, temp)) * parse(formula.substring(temp + 1));
        }

        temp = formula.lastIndexOf("/");
        if (temp != -1) {
    
    
            return parse(formula.substring(0, temp)) / parse(formula.substring(temp + 1));
        }

        return Double.parseDouble(formula);
    }

}

3. Encoding

1. UI interface design

An elegant computing interface might have buttons with similar functions using the same UI style.

(1) Button style design

• Calculation symbols

For example, basic addition, subtraction, multiplication and division (+, -, *, /) and equals (=)

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--设置颜色-->
    <solid android:color="#A7DD4E2E"
        />
    <!--设置圆角-->

    <corners android:radius="90dp"/>

    <size
        android:width="90dp"
        android:height="90dp"/>

</shape>

• number

I looked at some calculators and there are number buttons like 00, Teku La

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--设置颜色-->
    <solid android:color="#A6282828"
        />
    <!--设置圆角-->

    <corners android:radius="90dp"/>

    <size
        android:width="90dp"
        android:height="90dp"/>

</shape>

• special

For example, AC: clear

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--设置颜色-->
    <solid android:color="#A7989595"
        />
    <!--设置圆角-->

    <corners android:radius="90dp"/>

    <size
        android:width="90dp"
        android:height="90dp" />

</shape>

(2) Main interface layout design

        Regarding the main interface, I further optimized it, mainly referring to the computer styles of many mobile phones, and found that this style looks very friendly to the eyes.

<?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"
    tools:context=".MainActivity"
    android:orientation="vertical"
    android:background="#6F6A6A">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:id="@+id/jsq_text"
            android:layout_width="match_parent"
            android:layout_height="60dp"
            android:background="#FFFFFF"
            android:textSize="25dp"
            android:gravity="right"
            android:layout_marginTop="30dp"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:gravity="center">

        <Button
            android:id="@+id/ac"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="AC"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape"/>

        <Button
            android:id="@+id/fang"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+/-"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape"/>

        <Button
            android:id="@+id/yu"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="%"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape" />

        <Button
            android:id="@+id/chu"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="/"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ceng"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <Button
            android:id="@+id/one"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="1"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/two"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="2"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/there"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="3"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei" />

        <Button
            android:id="@+id/jia"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ceng"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <Button
            android:id="@+id/four"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="4"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/five"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="5"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/six"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="6"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei" />

        <Button
            android:id="@+id/jiang"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="-"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ceng"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <Button
            android:id="@+id/seven"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="7"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/event"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="8"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei"/>

        <Button
            android:id="@+id/nine"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="9"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei" />

        <Button
            android:id="@+id/cheng"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="*"
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ceng"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <Button
            android:id="@+id/zero"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0"
            android:layout_margin="10dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ling"/>

        <Button
            android:id="@+id/dian"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="."
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_hei" />

        <Button
            android:id="@+id/dengyu"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="="
            android:layout_margin="5dp"
            android:textSize="25dp"
            android:background="@drawable/shape_ceng"/>

    </LinearLayout>

</LinearLayout>

2. Encoding

(1) Control initialization

Those who are familiar with my coding style will know that it is bound control information without looking at it.

	Button zero,one,two,there,four,five,six,seven,event,nine;
    Button jia,jiang,cheng,chu;
    Button dian,dengyu,ac;
    TextView text;

    private void init() {
    
    
        zero = findViewById(R.id.zero);
        one = findViewById(R.id.one);
        two = findViewById(R.id.two);
        there = findViewById(R.id.there);
        four = findViewById(R.id.four);
        five = findViewById(R.id.five);
        six = findViewById(R.id.six);
        seven = findViewById(R.id.seven);
        event = findViewById(R.id.event);
        nine = findViewById(R.id.nine);

        jia = findViewById(R.id.jia);
        jiang = findViewById(R.id.jiang);
        cheng = findViewById(R.id.cheng);
        chu = findViewById(R.id.chu);

        dian = findViewById(R.id.dian);
        dengyu = findViewById(R.id.dengyu);

        text = findViewById(R.id.jsq_text);
        ac = findViewById(R.id.ac);

        zero.setOnClickListener(clickListener);
        one.setOnClickListener(clickListener);
        two.setOnClickListener(clickListener);
        there.setOnClickListener(clickListener);
        four.setOnClickListener(clickListener);
        five.setOnClickListener(clickListener);
        six.setOnClickListener(clickListener);
        seven.setOnClickListener(clickListener);
        event.setOnClickListener(clickListener);
        zero.setOnClickListener(clickListener);
        nine.setOnClickListener(clickListener);
        jia.setOnClickListener(clickListener);
        jiang.setOnClickListener(clickListener);
        cheng.setOnClickListener(clickListener);
        chu.setOnClickListener(clickListener);
        dian.setOnClickListener(clickListener);
        dengyu.setOnClickListener(clickListener);
        ac.setOnClickListener(clickListener);
    }

(2) Event listener

Mainly responsible for data rendering and algorithm reference

    public View.OnClickListener clickListener = new View.OnClickListener() {
    
    
        /**
         * Called when a view has been clicked.
         *
         * @param v The view that was clicked.
         */
        @Override
        public void onClick(View v) {
    
    
            switch (v.getId()) {
    
    
                case R.id.zero:
                    js += "0";
                    text.setText(js);
                    break;
                case R.id.one:
                    js += "1";
                    text.setText(js);
                    break;
                case R.id.two:
                    js += "2";
                    text.setText(js);
                    break;
                case R.id.there:
                    js += "3";
                    text.setText(js);
                    break;
                case R.id.four:
                    js += "4";
                    text.setText(js);
                    break;
                case R.id.five:
                    js += "5";
                    text.setText(js);
                    break;
                case R.id.six:
                    js += "6";
                    text.setText(js);
                    break;
                case R.id.seven:
                    js += "7";
                    text.setText(js);
                    break;
                case R.id.event:
                    js += "8";
                    text.setText(js);
                    break;
                case R.id.nine:
                    js += "9";
                    text.setText(js);
                    break;
                case R.id.jia:
                    js += "+";
                    text.setText(js);
                    break;
                case R.id.jiang:
                    js += "-";
                    text.setText(js);
                    break;
                case R.id.cheng:
                    js += "*";
                    text.setText(js);
                    break;
                case R.id.chu:
                    js += "/";
                    text.setText(js);
                    break;
                case R.id.dian:
                    js += ".";
                    text.setText(js);
                    break;
                case R.id.dengyu:
                    double a = alg.parse(js);
                    text.setText(String.valueOf(a));
                    break;
                case R.id.ac:
                    js = "";
                    text.setText(js);
                    break;
            }
        }
    };

4. Accessories

Source code: https://download.csdn.net/download/weixin_48916759/87935078