Android studio 设计简易的计算器-662P.COM

效果显示：

第一步，简单的界面布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity"
    android:background="#000000">
    <TextView
        android:id="@+id/text1"
        android:layout_width="match_parent"
        android:layout_height="170dp"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:layout_marginRight="10dp"
        android:background="#ffffff"
        android:gravity="right|bottom"
        android:hint="0"
        android:paddingRight="5dp"
        android:textColor="#000000"
        android:textSize="40sp" />
    <LinearLayout
        android:id="@+id/relative"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginLeft="10dp"
        android:orientation="vertical">
        <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
        <Button
            android:id="@+id/btn_7"
            style="@style/ButtonStyle"
            android:text="@string/btn_7" />
        <Button
            android:id="@+id/btn_8"
            style="@style/ButtonStyle"
            android:text="@string/btn_8" />
        <Button
            android:id="@+id/btn_9"
            style="@style/ButtonStyle"
            android:text="@string/btn_9" />
        <Button
            android:id="@+id/btn_clear"
            style="@style/ButtonStyle"
            android:text="@string/btn_clear"/>
    </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <Button
                android:id="@+id/btn_4"
                style="@style/ButtonStyle"
                android:text="@string/btn_4" />
            <Button
                android:id="@+id/btn_5"
                style="@style/ButtonStyle"
                android:text="@string/btn_5" />
            <Button
                android:id="@+id/btn_6"
                style="@style/ButtonStyle"
                android:text="@string/btn_6" />
            <Button
                android:id="@+id/btn_plus"
                style="@style/ButtonStyle"
                android:text="@string/btn_plus"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <Button
                android:id="@+id/btn_1"
                style="@style/ButtonStyle"
                android:text="@string/btn_1" />
            <Button
                android:id="@+id/btn_2"
                style="@style/ButtonStyle"
                android:text="@string/btn_2" />
            <Button
                android:id="@+id/btn_3"
                style="@style/ButtonStyle"
                android:text="@string/btn_3" />
            <Button
                android:id="@+id/btn_minus"
                style="@style/ButtonStyle"
                android:text="@string/btn_minus"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <Button
                android:id="@+id/btn_0"
                style="@style/ButtonStyle"
                android:text="@string/btn_0" />
            <Button
                android:id="@+id/btn_equal"
                style="@style/ButtonEqualStyle"
                android:text="@string/btn_equal" />
            <Button
                android:id="@+id/btn_divide"
                style="@style/ButtonStyle"
                android:text="@string/btn_divide" />
            <Button
                android:id="@+id/btn_multiply"
                style="@style/ButtonStyle"
                android:text="@string/btn_multiply"/>
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

string.xml文件

<resources>
    <string name="app_name">计算器</string>
    <string name="text1">显示文本框</string>
    <string name="relative">布局</string>
    <string name="btn_1">1</string>
    <string name="btn_2">2</string>
    <string name="btn_3">3</string>
    <string name="btn_4">4</string>
    <string name="btn_5">5</string>
    <string name="btn_6">6</string>
    <string name="btn_7">7</string>
    <string name="btn_8">8</string>
    <string name="btn_9">9</string>
    <string name="btn_0">0</string>
    <string name="btn_clear">C</string>
    <string name="btn_plus">+</string>
    <string name="btn_minus">-</string>
    <string name="btn_multiply">×</string>
    <string name="btn_divide">÷</string>
    <string name="btn_equal">=</string>
</resources>

采用的是LinearLayout线性布局，而因为按钮的基本属性相同，所以采用使用样式的方式来设置，代码如下

<resources>
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>
    <style name="ButtonBaseStyle">
        <item name="android:layout_width">40dp</item>
        <item name="android:layout_height">70dp</item>
        <item name="android:layout_margin">10dp</item>
        <item name="android:padding">10dp</item>
        <item name="android:textColor">@android:color/black</item>
        <item name="android:textSize">30sp</item>
    </style>
    <style name="ButtonStyle" parent="ButtonBaseStyle">
        <item name="android:background">@drawable/bg_selector</item>
        <item name="android:layout_weight">1</item>
    </style>
    <style name="ButtonEqualStyle" parent="ButtonBaseStyle">
        <item name="android:background">@drawable/ping_bg</item>
        <item name="android:layout_weight">1</item>
    </style>
</resources>

white_bg.xml文件

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<corners android:radius="5dp"/>
    <solid android:color="#ffffff"/>
</shape>

pink_bg.xml文件

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<corners android:radius="5dp"></corners>
    <solid android:color="#ee82ee"></solid>
</shape>

selector_bg.xml文件

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/white_bg" android:state_pressed="false"></item>
    <item android:drawable="@drawable/ping_bg"
        android:state_pressed="true"></item>
</selector>

事件Java代码

为了简单快捷的给各个按钮设置监听事件，将按钮都放在一个数组里面，然后使用for语句给按钮添加监听事件。

在onClick()放中，首先会获取文本框的id（注意是文本框的id）。

然后获取文本框里面的输入。获取字符串后，使用switch或者for语句对点击的按钮进行判断，当只点击数字按钮0到9时，输入不会break掉，只会将前面所有的字符连接组成字符串显示在文本框里。

注意：如果点击的第一个数字是0，那么就只显示0后面输入的数字。

package com.example.exp3;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        int[] ids = {R.id.btn_0, R.id.btn_1, R.id.btn_2, R.id.btn_3, R.id.btn_4, R.id.btn_4,
                R.id.btn_5, R.id.btn_6, R.id.btn_7, R.id.btn_8, R.id.btn_9, R.id.btn_equal,
                R.id.btn_clear, R.id.btn_multiply, R.id.btn_minus, R.id.btn_divide, R.id.btn_plus};
        //将所有按钮整合成一个数组
        for (int i = 0; i < ids.length; i++)
            findViewById(ids[i]).setOnClickListener(this);//给每个按钮设置一个监听事件
    }
    @Override
    public void onClick(View v) {
        TextView tv_input = (TextView) findViewById(R.id.text1);
        Button btn = (Button)v;
        String str=tv_input.getText().toString();//获取xml那里的输入
        String strButton =btn.getText().toString();//点击按钮得到的文本
        switch (v.getId()){
            case R.id.btn_0:
            case R.id.btn_1:
            case R.id.btn_2:
            case R.id.btn_3:
            case R.id.btn_4:
            case R.id.btn_5:
            case R.id.btn_6:
            case R.id.btn_7:
            case R.id.btn_8:
            case R.id.btn_9:
                if (str.equals("0"))
                    tv_input.setText(strButton);
                else
                    tv_input.setText(str+strButton);
                break;
            case R.id.btn_clear:
                tv_input.setText("0");
                break;
            case R.id.btn_plus:
            case R.id.btn_minus:
            case R.id.btn_multiply:
            case R.id.btn_divide:
                tv_input.setText(str+strButton);
                break;
            case R.id.btn_equal:
                MyCalc obj=new MyCalc(str);
                double ret = obj.Calc();
                int Ret = (int)ret;
                if (ret == Ret)
                    tv_input.setText(String.valueOf(Ret));
                else
                    tv_input.setText(String.valueOf(ret));
                break;
        }
    }
    class MyCalc {
        private String input;
        public MyCalc(String input) {
            this.input = input;
        }
        public double Calc() {
            if (TextUtils.isEmpty(input))
                return 0;
            Pattern pattern = Pattern.compile("[+(×)(÷)/-]");
            String[] nums = pattern.split(input);
            Matcher matcher = pattern.matcher(input);
            if (matcher.find() == false)
                return 0;
            String op = matcher.group(0);
            double first = Double.parseDouble(nums[0]);
            double second = Double.parseDouble(nums[1]);
            double sum = 0;
            try {
                switch (op) {
                    case "+":
                        sum = first + second;
                        break;
                    case "-":
                        sum = first - second;
                        break;
                    case "×":
                        sum = first * second;
                        break;
                    case "÷":
                        sum = first / second;
                        break;
                }
            } catch (Exception e) {
                Toast.makeText(MainActivity.this, "出错", Toast.LENGTH_LONG).show();
            }
            return sum;
        }
    }
}

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