【Android】Introduction to Controls and Layout-Simple Calculator

Enterprise 2023-09-30 04:07:45 views: null

Table of contents

1. Basic development environment

2. Calculator layout and related buttons

3. The main operation logic of the calculator

4. APK files

5. Project source code

1. Basic development environment

JDK：JDK17

Android Studio：Android Studio Giraffe | 2022.3.1

Android SDK：Android API 34

Gradle: gradle-8.0-bin.zip

2. Calculator layout and related buttons

Use LinearLayout and GridLayout to implement the interactive front end of the calculator.

The layout file is as follows

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#EEEEEE"
    android:orientation="vertical"
    android:padding="5dp">

    <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="match_parent"
                android:gravity="center"
                android:text="@string/simple_calculator"
                android:textColor="@color/black"
                android:textSize="20sp"/>

            <TextView
                android:id="@+id/tv_result"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@color/white"
                android:lines="3"
                android:text="@string/filler"
                android:gravity="end|bottom"
                android:textColor="@color/black"
                android:textSize="25sp"/>

            <GridLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:columnCount="4"
                android:rowCount="5">

                <Button
                    android:id="@+id/btn_clear_entry"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/cancel"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_divide"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/divide"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_multiply"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/multiply"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_clear"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/delete"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_seven"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/seven"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_eight"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/eight"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_nine"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/nine"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_plus"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/plus"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_four"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/four"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_five"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/five"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_six"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/six"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_minus"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/minus"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_one"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/one"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_two"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/two"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_three"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/three"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_sqrt"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/sqrt"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_reciprocal"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/reciprocal"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_zero"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/zero"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_dot"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/dot"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

                <Button
                    android:id="@+id/btn_equal"
                    android:layout_width="0dp"
                    android:layout_height="@dimen/button_height"
                    android:layout_columnWeight="1"
                    android:gravity="center"
                    android:text="@string/equal"
                    android:textColor="@color/black"
                    android:textSize="@dimen/button_font_size"/>

            </GridLayout>

        </LinearLayout>

    </ScrollView>


</LinearLayout>

The relevant values ​​are as follows:

  • strings.xml
<resources>
    <string name="app_name">calculator</string>
    <string name="simple_calculator">计算器</string>
    <string name="filler">0</string>
    <string name="cancel">CE</string>
    <string name="divide">÷</string>
    <string name="multiply">×</string>
    <string name="plus">+</string>
    <string name="minus">-</string>
    <string name="delete">C</string>
    <string name="zero">0</string>
    <string name="one">1</string>
    <string name="two">2</string>
    <string name="three">3</string>
    <string name="four">4</string>
    <string name="five">5</string>
    <string name="six">6</string>
    <string name="seven">7</string>
    <string name="eight">8</string>
    <string name="nine">9</string>
    <string name="sqrt">√</string>
    <string name="dot">.</string>
    <string name="equal">=</string>
    <string name="reciprocal">1/X</string>
</resources>
  • dimens.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <dimen name="button_font_size">30sp</dimen>
    <dimen name="button_height">75dp</dimen>
</resources>

actual effect:

 

3. The main operation logic of the calculator

package com.example.calculator;

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

import androidx.appcompat.app.AppCompatActivity;

import java.util.Arrays;
import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tvResult;

    private String firstNum = "";
    private String secondNum = "";
    private String operator = "";
    private String result = "";
    private String showText = "";

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

        // 从布局文件中获取文本视图
        tvResult = findViewById(R.id.tv_result);

        // 为所有按钮注册点击监听器
        findViewById(R.id.btn_clear_entry).setOnClickListener(this);
        findViewById(R.id.btn_divide).setOnClickListener(this);
        findViewById(R.id.btn_multiply).setOnClickListener(this);
        findViewById(R.id.btn_clear).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_plus).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_sqrt).setOnClickListener(this);
        findViewById(R.id.btn_reciprocal).setOnClickListener(this);
        findViewById(R.id.btn_zero).setOnClickListener(this);
        findViewById(R.id.btn_dot).setOnClickListener(this);
        findViewById(R.id.btn_equal).setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        String inputText = ((TextView) view).getText().toString();

        List<Integer> fourOperations = Arrays.asList(R.id.btn_plus, R.id.btn_minus, R.id.btn_multiply, R.id.btn_divide);
        int id = view.getId();

        if (id == R.id.btn_clear) {
            // 清除
            clear();
        } else if (id == R.id.btn_clear_entry) {
            // 清除输入
            clearEntryOperate();
        } else if (fourOperations.contains(id)) {
            operator = inputText;
            refreshShowText(showText + operator);
            // 四则运算
        } else if (id == R.id.btn_equal) {
            // 等号
            if (!secondNum.equals("")) {
                double calculateResult = calculateFour();
                refreshOperateResult(String.valueOf(calculateResult));
                refreshShowText(result);
            }
        } else if (id == R.id.btn_sqrt) {
            // 根号
            double sqrtResult = Math.sqrt(Double.parseDouble(firstNum));
            refreshOperateResult(String.valueOf(sqrtResult));
            refreshShowText(result);
        } else if (id == R.id.btn_reciprocal) {
            // 倒数
            double reciprocalResult = 1.0 / Double.parseDouble(firstNum);
            refreshOperateResult(String.valueOf(reciprocalResult));
            refreshShowText(result);
        } else {
            // 其它
            if (result.length() > 0 && operator.equals("")) {
                clear();
            }

            if (operator.equals("")) {
                firstNum += inputText;
            } else {
                secondNum += inputText;
            }
            if (showText.equals("0") && !inputText.equals(".")) {
                refreshShowText(inputText);
            } else {
                refreshShowText(showText + inputText);
            }

        }
    }

    private double calculateFour() {
        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);
            default:
                return Double.parseDouble(firstNum) / Double.parseDouble(secondNum);
        }
    }

    private void clear() {
        refreshOperateResult("");
        refreshShowText("0");
    }

    private void refreshOperateResult(String newResult) {
        result = newResult;
        firstNum = result;
        secondNum = "";
        operator = "";

    }

    private void clearEntryOperate() {
        String tmp = showText.substring(0, showText.length() - 1);
        if (tmp.equals("")) {
            tmp = "0";
        }
        refreshShowText(tmp);
    }

    // 刷新显示文本
    private void refreshShowText(String text) {
        showText = text;
        integerRemoveDot();
        tvResult.setText(showText);
    }

    private void integerRemoveDot() {
        int start = showText.indexOf(".");
        if (start != -1) {
            int end = showText.length();
            String value = showText.substring(start + 1, end);
            if (Double.parseDouble(value) == 0.0) {
                showText = showText.substring(0, start);
            }
        }
    }
}

4. APK files

The built APK file can be found at the beginning of the file and can be downloaded and installed directly.

5. Project source code

https://gitee.com/hl0929/calculator

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