一个计算器Android程序的源码部分分为主干和细节两部分。
一、主干
1. 主干的构成
- 计算器的布局
- 事件（即计算器上的按钮、文本框）监听
- 实现计算
2. 详细解释
假设我们的项目名为Calculator，而布局名称（Layout Name）为默认的activity_main 。即设置如下图所示：
在这种前提下，有：
- 设置计算器布局的文件：Calculator/app/src/main/res/layout/activity_main.xml
- 事件监听和计算实现在同一个文件里：Calculator/app/src/main/java/下的一个子目录里的MainActivity.java
即如下图所示：
3. 主干代码部分
- 计算器布局代码（写在activity_main.xml文件里）：
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<EditText
android:id="@+id/input"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:editable="false"
android:hint="@string/shuru" /> <EditText
android:id="@+id/output"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:editable="true"
android:gravity="right"
android:hint="@string/shuchu" /> <RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content" > <Button
android:id="@+id/seven"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentLeft="true"
android:text="@string/seven"
android:textSize="40sp" /> <Button
android:id="@+id/eight"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_toRightOf="@id/seven"
android:text="@string/eight"
android:textSize="40sp" /> <Button
android:id="@+id/nine"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_toRightOf="@id/eight"
android:text="@string/nine"
android:textSize="40sp" /> <Button
android:id="@+id/add"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentRight="true"
android:layout_toRightOf="@id/nine"
android:text="@string/add"
android:textSize="40sp" /> <Button
android:id="@+id/four"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentLeft="true"
android:layout_below="@id/seven"
android:text="@string/four"
android:textSize="40sp" /> <Button
android:id="@+id/five"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/eight"
android:layout_toRightOf="@id/four"
android:text="@string/five"
android:textSize="40sp" /> <Button
android:id="@+id/six"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/nine"
android:layout_toRightOf="@id/five"
android:text="@string/six"
android:textSize="40sp" /> <Button
android:id="@+id/subtract"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentRight="true"
android:layout_below="@id/add"
android:layout_toRightOf="@id/six"
android:text="@string/subtract"
android:textSize="40sp" /> <Button
android:id="@+id/one"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentLeft="true"
android:layout_below="@id/four"
android:text="@string/one"
android:textSize="40sp" /> <Button
android:id="@+id/two"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/five"
android:layout_toRightOf="@id/one"
android:text="@string/two"
android:textSize="40sp" /> <Button
android:id="@+id/three"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/six"
android:layout_toRightOf="@id/two"
android:text="@string/three"
android:textSize="40sp" /> <Button
android:id="@+id/multiply"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentRight="true"
android:layout_below="@id/subtract"
android:layout_toRightOf="@id/three"
android:text="@string/multiply"
android:textSize="40sp" /> <Button
android:id="@+id/zero"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentLeft="true"
android:layout_below="@id/one"
android:text="@string/zero"
android:textSize="40sp" /> <Button
android:id="@+id/clear"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/two"
android:layout_toRightOf="@id/zero"
android:text="@string/clear"
android:textSize="40sp" /> <Button
android:id="@+id/result"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_below="@id/three"
android:layout_toRightOf="@id/clear"
android:text="@string/result"
android:textSize="40sp" /> <Button
android:id="@+id/divide"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentRight="true"
android:layout_below="@id/multiply"
android:layout_toRightOf="@id/result"
android:text="@string/divide"
android:textSize="40sp" /> <Button
android:id="@+id/dot"
android:layout_width="80dp"
android:layout_height="70dp"
android:layout_alignParentLeft="true"
android:layout_below="@id/zero"
android:text="@string/dot"
android:textSize="40sp" />
<Button
android:id="@+id/writeButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@id/dot"
android:text="@string/write"
android:textSize="40sp" />
<Button
android:id="@+id/readButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_below="@id/dot"
android:text="@string/read"
android:textSize="40sp" /> <CheckBox
android:id="@+id/appendBox"
android:text="@string/appendBox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toLeftOf="@+id/divide"
android:layout_toStartOf="@+id/divide"
android:layout_marginBottom="12dp"
/> </RelativeLayout> <EditText android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/textView" /> <EditText android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/displayView" /> <EditText
android:id="@+id/errorzero"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:editable="false"
android:gravity="center"
/>
<EditText
android:id="@+id/resultText"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:editable="false"
android:gravity="left"
android:text="@string/resultText"
/>
</LinearLayout>
</ScrollView>
- 事件监听和实现计算代码（写在MainActivity.java文件里）
package com.example.lenovo.calculator;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class MainActivity extends Activity {
/**
* Called when the activity is first created.
*/
private EditText output = null;
private EditText input = null;
private Button btn0 = null;
private Button btn1 = null;
private Button btn2 = null;
private Button btn3 = null;
private Button btn4 = null;
private Button btn5 = null;
private Button btn6 = null;
private Button btn7 = null;
private Button btn8 = null;
private Button btn9 = null;
private Button btnadd = null;
private Button btnsubtract = null;
private Button btnmultiply = null;
private Button btndivide = null;
private Button btnclear = null;
private Button btnresult = null;
private Button btndot = null;
private EditText errorzero = null;
private EditText resultText = null;
private Button writeButton = null;
private Button readButton = null;
private CheckBox appendBox = null;
private EditText textView = null;
private EditText displayView = null;
public String FILE_NAME = "fileDemo.txt";
private String str = "";//保存数字
private String strold = "";//原数字
private char act = ' ';//记录“加减乘除等于”符号
private int count = 0;//判断要计算的次数，如果超过一个符号，先算出来一部分
private Float result = null;//计算的输出结果
private Boolean errBoolean = false;//有错误的时候为true，无错为false
private Boolean flagBoolean = false;//一个标志，如果为true，可以响应运算消息，如果为false，不响应运算消息，只有前面是数字才可以响应运算消息
private Boolean flagDot = false; //小数点标志位
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
output = (EditText) findViewById(R.id.output);
input = (EditText) findViewById(R.id.input);
errorzero = (EditText) findViewById(R.id.errorzero);
resultText = (EditText) findViewById(R.id.resultText);
writeButton = (Button) findViewById(R.id.writeButton);
readButton = (Button) findViewById(R.id.readButton);
textView = (EditText) findViewById(R.id.textView);
displayView = (EditText) findViewById(R.id.displayView);
appendBox = (CheckBox) findViewById(R.id.appendBox);
btn0 = (Button) findViewById(R.id.zero);
btn1 = (Button) findViewById(R.id.one);
btn2 = (Button) findViewById(R.id.two);
btn3 = (Button) findViewById(R.id.three);
btn4 = (Button) findViewById(R.id.four);
btn5 = (Button) findViewById(R.id.five);
btn6 = (Button) findViewById(R.id.six);
btn7 = (Button) findViewById(R.id.seven);
btn8 = (Button) findViewById(R.id.eight);
btn9 = (Button) findViewById(R.id.nine);
btnadd = (Button) findViewById(R.id.add);
btnsubtract = (Button) findViewById(R.id.subtract);
btnmultiply = (Button) findViewById(R.id.multiply);
btndivide = (Button) findViewById(R.id.divide);
btnclear = (Button) findViewById(R.id.clear);
btnresult = (Button) findViewById(R.id.result);
btndot = (Button) findViewById(R.id.dot);
//设置按钮侦听事件
btn0.setOnClickListener(listener);
btn1.setOnClickListener(listener);
btn2.setOnClickListener(listener);
btn3.setOnClickListener(listener);
btn4.setOnClickListener(listener);
btn5.setOnClickListener(listener);
btn6.setOnClickListener(listener);
btn7.setOnClickListener(listener);
btn8.setOnClickListener(listener);
btn9.setOnClickListener(listener);
//执行运算
btnadd.setOnClickListener(listener);
btnsubtract.setOnClickListener(listener);
btnmultiply.setOnClickListener(listener);
btndivide.setOnClickListener(listener);
btnclear.setOnClickListener(listener);
btnresult.setOnClickListener(listener);
btndot.setOnClickListener(listener);
writeButton.setOnClickListener(writelistener);
readButton.setOnClickListener(readlistener);
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
}
private OnClickListener listener = new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
//输入数字
case R.id.zero:
num(0);
break;
case R.id.one:
num(1);
break;
case R.id.two:
num(2);
break;
case R.id.three:
num(3);
break;
case R.id.four:
num(4);
break;
case R.id.five:
num(5);
break;
case R.id.six:
num(6);
break;
case R.id.seven:
num(7);
break;
case R.id.eight:
num(8);
break;
case R.id.nine:
num(9);
break;
case R.id.dot:
dot();
break;
//执行运算
case R.id.add:
add();
break;
case R.id.subtract:
sub();
break;
case R.id.multiply:
multiply();
break;
case R.id.divide:
divide();
break;
case R.id.clear:
clear();
break;
//计算结果
case R.id.result:
result();
if (!errBoolean && flagBoolean) {
output.setText(String.valueOf(result));
}
resultText.setText(strold + act + str + "=" + result+" ");
break;
default:
break;
}
input.setText(strold + act + str);
output.setText(String.valueOf(result));
}
};
private OnClickListener writelistener = new OnClickListener() {
@Override
public void onClick(View view) {
//textView.setText("");
FileOutputStream fos = null;
try {
if (appendBox.isChecked()) {
fos = openFileOutput(FILE_NAME, Context.MODE_APPEND);
} else {
fos = openFileOutput(FILE_NAME, Context.MODE_PRIVATE);
}
String text = resultText.getText().toString();
fos.write(text.getBytes());
textView.setText("文件写入成功，写入长度：" + text.length());
//resultText.setText("");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally {
if (fos != null)
try {
fos.flush();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
};
private OnClickListener readlistener = new OnClickListener() {
@Override
public void onClick(View view) {
displayView.setText("");
FileInputStream fis = null;
try {
fis = openFileInput(FILE_NAME);
if (fis.available() == 0) {
return;
}
byte[] readBytes = new byte[fis.available()];
while (fis.read(readBytes) != -1) {
}
String text = new String(readBytes);
displayView.setText(text);
textView.setText("文件读取成功，写入长度：" + text.length());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
};
private void dot() {
// TODO Auto-generated method stub
if (!flagDot) {
str = str + ".";
flagBoolean = false;
flagDot = true;
}
}
private void clear() {
// TODO Auto-generated method stub
str = strold = "";
count = 0;
act = ' ';
result = null;
flagBoolean = false;
flagDot = false;
input.setText(strold + act + str);
output.setText("");
errorzero.setText("");
displayView.setText("");
textView.setText("");
resultText.setText("");
}
private void divide() {
// TODO Auto-generated method stub
if (flagBoolean) {
check();
act = '/';
flagBoolean = false;
}
}
private void multiply() {
// TODO Auto-generated method stub
if (flagBoolean) {
check();
act = '*';
flagBoolean = false;
}
}
private void sub() {
// TODO Auto-generated method stub
if (flagBoolean) {
check();
act = '-';
flagBoolean = false;
}
}
private void add() {
// TODO Auto-generated method stub
if (flagBoolean) {
check();
act = '+';
flagBoolean = false;
}
}
private void check() {
// TODO Auto-generated method stub
if (count >= 1) {
result();
str = String.valueOf(result);
}
strold = str;
str = "";
count++;
flagDot = false;
errorzero.setText("");
}
//计算输出结果
private void result() {
// TODO Auto-generated method stub
if (flagBoolean) {
Float a, b;
a = Float.parseFloat(strold);
b = Float.parseFloat(str);
if (b == 0 && act == '/') {
clear();
errorzero.setText("除数不能为零!");
//output.setText("除数不能为零!");
//errBoolean=true;
}
if (!errBoolean) {
switch (act) {
case '+':
result = a + b;
break;
case '-':
result = a - b;
break;
case '*':
result = a * b;
break;
case '/':
result = a / b;
break;
default:
break;
}
}
}
}
private void num(int i) {
// TODO Auto-generated method stub
str = str + String.valueOf(i);
flagBoolean = true;
errorzero.setText("");
}
}
二、细节
仅仅将主*分代码copy下来并不能运行程序，因为主干代码调用了一些文件的代码，这些文件就是我们所说的细节。
1. 字符串资源
- 文件位置：Calculator/app/src/main/res/values/strings.xml
- 代码部分：
<resources>
<string name="app_name">Calculator</string>
<string name="action_settings">Settings</string>
<string name="zero">0</string>
<string name="one">1</string>
<string name="two">2</string>
<string name="three">3</string>
<string name="four">4</string>
<string name="five">5</string>
<string name="six">6</string>
<string name="seven">7</string>
<string name="eight">8</string>
<string name="nine">9</string>
<string name="add">+</string>
<string name="subtract">-</string>
<string name="multiply">*</string>
<string name="divide">/</string>
<string name="clear">CE</string>
<string name="result">=</string>
<string name="shuru">请按数字键盘输入数字</string>
<string name="shuchu">计算器输出结果</string>
<string name="dot">.</string>
<string name="write">写入</string>
<string name="read">读取</string>
<string name="resultText">计算式</string>
<string name="appendBox">追加模式</string> </resources>
2. 其他可能要改的文件
- Calculator/app/src/main/res/drawable：设置相关的背景颜色、按钮特效
- Calculator/app/src/main/AndroidManifest.xml：设置这个项目的整体配置
三、备注
- 本文提供的简易计算器仅需要修改前三个文件（布局文件、监听实现文件、字符串资源文件）
- 纯复制粘贴是一定会报错的，留意一点将有些地方改动一下