android应用程序--计算器

计算器在日常生活中用处还是比较大的，而且将其置入手机中，用起来更方便。而本次的任务是要运用MVC模式实现一个简易计算器。

阶段1、进行计算器的界面布局--V，这一阶段相对来说没有难度。

activity_calculate.xml文件：

 

string.xml文件中对各个控件的具体显示内容进行设置

    Calculate
    Hello world!
    Settings
    CalculateActivity
    运算符
     = 
    +
    -
    *
    /
     关于
    退出
    作者：牛灵玉\n版本:2.0
    确定
    取消
    

 

阶段2、编写计算器的业务逻辑类--M，实现计算器的加、减、乘、除基本功能

package com.edu.nly.model;

public class Calculator {
  public double add(double a,double b){
	  return a+b;
  }
  public double sub(double a,double b){
	  return a-b;
  }
  public double mul(double a,double b){
	  return a*b;
  }
  public double div(double a,double b){
	  return a/b;
  }
}

阶段3、4、5、编写Activity---C，查找组件并进行事件处理

package com.edu.nly;

import java.text.DecimalFormat;

import com.edu.nly.model.Calculator;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class CalculateActivity extends Activity {
	// 定义组件
	private EditText number1;// 操作数1文本框
	private EditText number2;// 操作数2文本框
	private TextView operate;// 运算符组件
	private TextView result;// 存放结果的组件
	private Button addButton;// 加法按钮组件
	private Button subButton;// 减法按钮组件
	private Button mulButton;// 乘法按钮组件
	private Button divButton;// 除法按钮组件
	private final static int MENU_ABOUT=1;
	private final static int MENU_EXIT=2;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_calculate);
		initialComponents();
		registerListener();
	}
    /*
     * 注册监听事件
     */
	private void registerListener() {
		
		addButton.setOnClickListener(new OnClickListener() {
			
			public void onClick(View v) {
				String num1String = number1.getText().toString().trim();
				String num2String = number2.getText().toString().trim();
				Log.e("第一个数：",num1String);
				Log.d("第二个数：",num2String);
				operate.setText("+");
				result.setText(Double.valueOf(new Calculator().add(
						Double.parseDouble(num1String),
						Double.parseDouble(num2String))).toString()  );
				
			}
		});
		subButton.setOnClickListener(new ButtonHander(){
			public void onClick(View v) {
				String num1String = number1.getText().toString().trim();
				String num2String = number2.getText().toString().trim();
				Log.e("第一个数：",num1String);
				Log.d("第二个数：",num2String);
				operate.setText("-");
				result.setText(Double.valueOf(calculator.sub(
						Double.parseDouble(num1String),
						Double.parseDouble(num2String))).toString());
				
			}
		});
		mulButton.setOnClickListener(new ButtonHander(){
			public void onClick(View v) {
				String num1String = number1.getText().toString().trim();
				String num2String = number2.getText().toString().trim();
				Log.e("第一个数：",num1String);
				Log.d("第二个数：",num2String);
				operate.setText("*");
				result.setText(format(calculator.mul(
						Double.parseDouble(num1String),
						Double.parseDouble(num2String))));
				
			}
		});
		divButton.setOnClickListener(new ButtonHander(){
			public void onClick(View v) {
				String num1String = number1.getText().toString().trim();
				String num2String = number2.getText().toString().trim();
				Log.e("第一个数：",num1String);
				Log.d("第二个数：",num2String);
				if("0".equals(num2String.trim())){
					Toast.makeText(CalculateActivity.this, "除数不能为零", Toast.LENGTH_LONG).show();
				}
				operate.setText("/");
				result.setText(format(calculator.div(
						Double.parseDouble(num1String),
						Double.parseDouble(num2String))));
				
			}
		});
		
	}

	/*
	 * 自定义初始化组件
	 */
	private void initialComponents() {
		number1 = (EditText) this.findViewById(R.id.num1);
		number2 = (EditText) this.findViewById(R.id.num2);
		operate = (TextView) this.findViewById(R.id.operate);
		result = (TextView) this.findViewById(R.id.result);
		addButton = (Button) this.findViewById(R.id.add);
		subButton = (Button) this.findViewById(R.id.sub);
		mulButton = (Button) this.findViewById(R.id.mul);
		divButton = (Button) this.findViewById(R.id.div);

	}

	private class ButtonHander implements OnClickListener {

		String num1String = number1.getText().toString().trim();
		String num2String = number2.getText().toString().trim();
     
		Calculator calculator = new Calculator();

		public void onClick(View v) {
			switch (v.getId()) {
			case R.id.add:
				operate.setText("+");
				break;
			case R.id.sub:
				operate.setText("-");
				break;
			case R.id.mul:
				operate.setText("*");
				break;
			case R.id.div:
				if("0".equals(num2String.trim())){
					Toast.makeText(CalculateActivity.this, "除数不能为零", Toast.LENGTH_LONG).show();
					break;
				}
				operate.setText("/");
				break;
			}

		}

	}
 
	public String format(double result) {
		DecimalFormat decimalFormat = new DecimalFormat("0.00");
		return decimalFormat.format(result);
	}
	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		int itemId=item.getItemId();
		switch(itemId){
		case MENU_ABOUT:
			AlertDialog.Builder alertDialog=new AlertDialog.Builder(this);
			alertDialog.setIcon(android.R.drawable.ic_menu_help);//引用系统自带的图标
			alertDialog.setTitle(R.string.about);//给对话框设置标题
			alertDialog.setMessage(R.string.info);//设置对话框的提示信息
			alertDialog.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
				
				
				public void onClick(DialogInterface dialog, int which) {
					Toast.makeText(CalculateActivity.this, "欢迎你的使用", Toast.LENGTH_LONG).show();
				}
			});
			alertDialog.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
				
				public void onClick(DialogInterface dialog, int which) {
				}
			});
			alertDialog.create().show();
			break;
		case MENU_EXIT:
			this.finish();
			break;
		}
		return true;
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		menu.add(0, MENU_ABOUT, 1, R.string.about);
		menu.add(0, MENU_EXIT, 2, R.string.exit);
		return true;
	}

}

经过上述操作之后的运行结果：

点击确定之后的运行结果：