Android实现加法计算器

<?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>

<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>

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;
 }
 }
 };
}