实战-Swing实现计算器

1 Swing实现计算器

我们可以借助Swing的事件处理功能来开发Java计算器。让我们看看在Java中创建计算器的代码。

package com.yiidian;

/*********************************************
Save this file as MyCalculator.java
to compile it use
	javac MyCalculator.java
to use the calcuator do this
	java MyCalculator

**********************************************/
import java.awt.*;
import java.awt.event.*;
/*********************************************/

public class MyCalculator extends Frame
{

public boolean setClear=true;
double number, memValue;
char op;

String digitButtonText[] = {"7", "8", "9", "4", "5", "6", "1", "2", "3", "0", "+/-", "." };
String operatorButtonText[] = {"/", "sqrt", "*", "%", "-", "1/X", "+", "=" };
String memoryButtonText[] = {"MC", "MR", "MS", "M+" };
String specialButtonText[] = {"Backspc", "C", "CE" };

MyDigitButton digitButton[]=new MyDigitButton[digitButtonText.length];
MyOperatorButton operatorButton[]=new MyOperatorButton[operatorButtonText.length];
MyMemoryButton memoryButton[]=new MyMemoryButton[memoryButtonText.length];
MySpecialButton specialButton[]=new MySpecialButton[specialButtonText.length];

Label displayLabel=new Label("0",Label.RIGHT);
Label memLabel=new Label(" ",Label.RIGHT);

final int FRAME_WIDTH=325,FRAME_HEIGHT=325;
final int HEIGHT=30, WIDTH=30, H_SPACE=10,V_SPACE=10;
final int TOPX=30, TOPY=50;
///////////////////////////
MyCalculator(String frameText)//constructor
{
super(frameText);

int tempX=TOPX, y=TOPY;
displayLabel.setBounds(tempX,y,240,HEIGHT);
displayLabel.setBackground(Color.BLUE);
displayLabel.setForeground(Color.WHITE);
add(displayLabel);

memLabel.setBounds(TOPX,  TOPY+HEIGHT+ V_SPACE,WIDTH, HEIGHT);
add(memLabel);

// set Co-ordinates for Memory Buttons
tempX=TOPX;	
y=TOPY+2*(HEIGHT+V_SPACE);
for(int i=0; i<memoryButton.length; i++)
{
memoryButton[i]=new MyMemoryButton(tempX,y,WIDTH,HEIGHT,memoryButtonText[i], this);
memoryButton[i].setForeground(Color.RED);
y+=HEIGHT+V_SPACE;
}

//set Co-ordinates for Special Buttons
tempX=TOPX+1*(WIDTH+H_SPACE); y=TOPY+1*(HEIGHT+V_SPACE);
for(int i=0;i<specialButton.length;i++)
{
specialButton[i]=new MySpecialButton(tempX,y,WIDTH*2,HEIGHT,specialButtonText[i], this);
specialButton[i].setForeground(Color.RED);
tempX=tempX+2*WIDTH+H_SPACE;
}

//set Co-ordinates for Digit Buttons
int digitX=TOPX+WIDTH+H_SPACE;
int digitY=TOPY+2*(HEIGHT+V_SPACE);
tempX=digitX;  y=digitY;
for(int i=0;i<digitButton.length;i++)
{
digitButton[i]=new MyDigitButton(tempX,y,WIDTH,HEIGHT,digitButtonText[i], this);
digitButton[i].setForeground(Color.BLUE);
tempX+=WIDTH+H_SPACE;
if((i+1)%3==0){tempX=digitX; y+=HEIGHT+V_SPACE;}
}

//set Co-ordinates for Operator Buttons
int opsX=digitX+2*(WIDTH+H_SPACE)+H_SPACE;
int opsY=digitY;
tempX=opsX;  y=opsY;
for(int i=0;i<operatorButton.length;i++)
{
tempX+=WIDTH+H_SPACE;
operatorButton[i]=new MyOperatorButton(tempX,y,WIDTH,HEIGHT,operatorButtonText[i], this);
operatorButton[i].setForeground(Color.RED);
if((i+1)%2==0){tempX=opsX; y+=HEIGHT+V_SPACE;}
}

addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent ev)
{System.exit(0);}
});

setLayout(null);
setSize(FRAME_WIDTH,FRAME_HEIGHT);
setVisible(true);
}
//////////////////////////////////
static String getFormattedText(double temp)
{
String resText=""+temp;
if(resText.lastIndexOf(".0")>0)
	resText=resText.substring(0,resText.length()-2);
return resText;
}
////////////////////////////////////////
public static void main(String []args)
{
new MyCalculator("计算器 - 一点教程网");
}
}

/*******************************************/

class MyDigitButton extends Button implements ActionListener
{
MyCalculator cl;

//////////////////////////////////////////
MyDigitButton(int x,int y, int width,int height,String cap, MyCalculator clc)
{
super(cap);
setBounds(x,y,width,height);
this.cl=clc;
this.cl.add(this);
addActionListener(this);
}
////////////////////////////////////////////////
static boolean isInString(String s, char ch)
{
for(int i=0; i<s.length();i++) if(s.charAt(i)==ch) return true;
return false;
}
/////////////////////////////////////////////////
public void actionPerformed(ActionEvent ev)
{
String tempText=((MyDigitButton)ev.getSource()).getLabel();

if(tempText.equals("."))
{
 if(cl.setClear) 
	{cl.displayLabel.setText("0.");cl.setClear=false;}
 else if(!isInString(cl.displayLabel.getText(),'.'))
	cl.displayLabel.setText(cl.displayLabel.getText()+".");
 return;
}

int index=0;
try{
        index=Integer.parseInt(tempText);
    }catch(NumberFormatException e){return;}

if (index==0 && cl.displayLabel.getText().equals("0")) return;

if(cl.setClear)
        	{cl.displayLabel.setText(""+index);cl.setClear=false;}
else
	cl.displayLabel.setText(cl.displayLabel.getText()+index);
}//actionPerformed
}//class defination

/********************************************/

class MyOperatorButton extends Button implements ActionListener
{
MyCalculator cl;

MyOperatorButton(int x,int y, int width,int height,String cap, MyCalculator clc)
{
super(cap);
setBounds(x,y,width,height);
this.cl=clc;
this.cl.add(this);
addActionListener(this);
}
///////////////////////
public void actionPerformed(ActionEvent ev)
{
String opText=((MyOperatorButton)ev.getSource()).getLabel();

cl.setClear=true;
double temp=Double.parseDouble(cl.displayLabel.getText());

if(opText.equals("1/x"))
	{
	try
		{double tempd=1/(double)temp;
		cl.displayLabel.setText(MyCalculator.getFormattedText(tempd));}
 	catch(ArithmeticException excp)
                		{cl.displayLabel.setText("Divide by 0.");}
	return;
	}
if(opText.equals("sqrt"))
	{
	try
		{double tempd=Math.sqrt(temp);
		cl.displayLabel.setText(MyCalculator.getFormattedText(tempd));}
        	catch(ArithmeticException excp)
	                {cl.displayLabel.setText("Divide by 0.");}
	return;
	}
if(!opText.equals("="))
	{
	cl.number=temp;
	cl.op=opText.charAt(0);
	return;
	}
// process = button pressed
switch(cl.op)
{
case '+':
	temp+=cl.number;break;
case '-':
	temp=cl.number-temp;break;
case '*':
	temp*=cl.number;break;
case '%':
	try{temp=cl.number%temp;}
	catch(ArithmeticException excp)
		{cl.displayLabel.setText("Divide by 0."); return;}
	break;
case '/':
	try{temp=cl.number/temp;}
        catch(ArithmeticException excp)
                {cl.displayLabel.setText("Divide by 0."); return;}
	break;
}//switch

cl.displayLabel.setText(MyCalculator.getFormattedText(temp));
//cl.number=temp;
}//actionPerformed
}//class

/****************************************/

class MyMemoryButton extends Button implements ActionListener
{
MyCalculator cl;

/////////////////////////////////
MyMemoryButton(int x,int y, int width,int height,String cap, MyCalculator clc)
{
super(cap);
setBounds(x,y,width,height);
this.cl=clc;
this.cl.add(this);
addActionListener(this);
}
////////////////////////////////////////////////
public void actionPerformed(ActionEvent ev)
{
char memop=((MyMemoryButton)ev.getSource()).getLabel().charAt(1);

cl.setClear=true;
double temp=Double.parseDouble(cl.displayLabel.getText());

switch(memop)
{
case 'C': 
	cl.memLabel.setText(" ");cl.memValue=0.0;break;
case 'R': 
	cl.displayLabel.setText(MyCalculator.getFormattedText(cl.memValue));break;
case 'S':
	cl.memValue=0.0;
case '+': 
	cl.memValue+=Double.parseDouble(cl.displayLabel.getText());
	if(cl.displayLabel.getText().equals("0") || cl.displayLabel.getText().equals("0.0")  )
		cl.memLabel.setText(" ");
	else 
		cl.memLabel.setText("M");	
	break;
}//switch
}//actionPerformed
}//class

/*****************************************/

class MySpecialButton extends Button implements ActionListener
{
MyCalculator cl;

MySpecialButton(int x,int y, int width,int height,String cap, MyCalculator clc)
{
super(cap);
setBounds(x,y,width,height);
this.cl=clc;
this.cl.add(this);
addActionListener(this);
}
//////////////////////
static String backSpace(String s)
{
String Res="";
for(int i=0; i<s.length()-1; i++) Res+=s.charAt(i);
return Res;
}

//////////////////////////////////////////////////////////
public void actionPerformed(ActionEvent ev)
{
String opText=((MySpecialButton)ev.getSource()).getLabel();
//check for backspace button
if(opText.equals("Backspc"))
{
String tempText=backSpace(cl.displayLabel.getText());
if(tempText.equals("")) 
	cl.displayLabel.setText("0");
else 
	cl.displayLabel.setText(tempText);
return;
}
//check for "C" button i.e. Reset
if(opText.equals("C")) 
{
cl.number=0.0; cl.op=' '; cl.memValue=0.0;
cl.memLabel.setText(" ");
}

//it must be CE button pressed
cl.displayLabel.setText("0");cl.setClear=true;
}//actionPerformed
}//class

/*********************************************

Features not implemented and few bugs

i)  No coding done for "+/-" button.
ii) Menubar is not included.
iii)Not for Scientific calculation
iv)Some of the computation may lead to unexpected result
   due to the representation of Floating point numbers in computer
   is an approximation to the given value that can be stored
   physically in memory.

***********************************************/

最终运行效果为：

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