安卓加法计算器

布局

<?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:orientation="vertical">
    <!-- 加法器名称-->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="加法器"
        android:textSize="40sp"
        android:textColor="#E6BD1A"
        android:gravity="center"
        android:layout_marginTop="20sp"
        android:textStyle="bold"/>

    <!-- 第1个数字输入框 -->
    <EditText
        android:id="@+id/input1"
        style="@style/input_style" />

    <!-- 加法符号 -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="+"
        android:textStyle="bold"
        android:textSize="40sp"
        android:textColor="#1A94E6"
        android:gravity="center"
        android:layout_marginTop="50sp"/>

    <!-- 第2个数字输入框-->
    <EditText
        android:id="@+id/input2"
        style="@style/input_style" />

    <!-- 等于和归零符号 -->
    <LinearLayout

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_gravity="center"
        android:layout_marginTop="20sp"
        android:layout_marginBottom="20sp">
        <!-- 等于符号 -->
        <Button
            android:id="@+id/btn1"
            style="@style/button_style"
            android:text="="
            android:layout_marginRight="20sp"/>
        <!-- 归零符号 -->
        <Button
            android:id="@+id/btn2"
            style="@style/button_style"
            android:text="C"/>

    </LinearLayout>

    <!-- 结果输入框 -->
    <EditText
        android:id="@+id/input3"
        style="@style/input_style"
        android:enabled="false"/>

</LinearLayout>

样式

<resources>

    <!-- Base application theme. -->
    <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>

    <!-- 3个输入框的样式 -->
    <style name="input_style">
        <item name="android:layout_gravity">center</item>
        <item name="android:gravity">center</item>
        <item name="android:layout_width">350sp</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:color">#000000</item>
        <item name="android:layout_marginTop">15sp</item>
        <item name="android:inputType">number</item>
    </style>

    <!-- 等于和归零按钮样式 -->
    <style name="button_style">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textSize">30sp</item>
        <item name="android:gravity">center</item>
    </style>

</resources>

java代码

package cn.itcast.totalizator;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    //输入框input1 input2
    // 结果框input3
    private EditText input1 = null;
    private EditText input2 = null;
    private EditText input3 = null;
    //等于按钮btn1
    //归零按钮btn2
    private Button btn1 = null;
    private Button btn2 = null;


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

        input1 = (EditText) findViewById(R.id.input1);
        input2 = (EditText) findViewById(R.id.input2);
        input3 = (EditText) findViewById(R.id.input3);

        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);

        //点击等于按钮触发监听事件
        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String input1Str = input1.getText().toString();
                String input2Str = input2.getText().toString();

                if (! input1Str.equals("") && ! input2Str.equals("")) {
                     double number1 = Double.parseDouble(input1Str);
                     double number2 = Double.parseDouble(input2Str);
                     double result = number1 + number2;

                     input3.setText(result + "");
                }
                else{
                    Toast.makeText(getApplicationContext(),"请输入合法的数字",Toast.LENGTH_SHORT).show();
                }
            }
        });
        //点击归零按钮触发监听事件
        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //把三个输入框都设置为空
                input1.setText("");
                input2.setText("");
                input3.setText("");
            }
        });


    }

    //点击退出按钮，弹出是否确认退出对话框
    @Override
    public void onBackPressed() {
        //声明对象
        AlertDialog dialog;
        //绑定当前界面窗口，设置标题
        dialog = new AlertDialog.Builder(this)
                .setTitle("Dialog对话框")
                .setMessage("是否确定退出")
                .setIcon(R.mipmap.ic_launcher)
                .setPositiveButton("确定",listener)
                .setNegativeButton("取消", listener)
                .create();
        dialog.show();

    }

    //监听对话框里面的button点击事件
    DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener()
    {
        public void onClick(DialogInterface dialog, int which)
        {
            switch (which)
            {
                case AlertDialog.BUTTON_POSITIVE:// "确认"按钮退出程序
                    finish();
                    break;
                case AlertDialog.BUTTON_NEGATIVE:// "取消"第二个按钮取消对话框
                    break;
                default:
                    break;
            }
        }
    };
}