制作一个简易计算器——基于Android Studio实现

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）：

  1 <?xml version="1.0" encoding="utf-8"?>
  2 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
  3     android:layout_width="fill_parent"
  4     android:layout_height="wrap_content"
  5     >
  6     <LinearLayout
  7         android:layout_width="fill_parent"
  8         android:layout_height="fill_parent"
  9         android:orientation="vertical" >
 10         <EditText
 11             android:id="@+id/input"
 12             android:layout_width="fill_parent"
 13             android:layout_height="wrap_content"
 14             android:layout_gravity="center"
 15             android:editable="false"
 16             android:hint="@string/shuru" />
 17 
 18         <EditText
 19             android:id="@+id/output"
 20             android:layout_width="fill_parent"
 21             android:layout_height="wrap_content"
 22             android:layout_gravity="center"
 23             android:editable="true"
 24             android:gravity="right"
 25             android:hint="@string/shuchu" />
 26 
 27         <RelativeLayout
 28             android:layout_width="fill_parent"
 29             android:layout_height="wrap_content" >
 30 
 31             <Button
 32                 android:id="@+id/seven"
 33                 android:layout_width="80dp"
 34                 android:layout_height="70dp"
 35                 android:layout_alignParentLeft="true"
 36                 android:text="@string/seven"
 37                 android:textSize="40sp" />
 38 
 39             <Button
 40                 android:id="@+id/eight"
 41                 android:layout_width="80dp"
 42                 android:layout_height="70dp"
 43                 android:layout_toRightOf="@id/seven"
 44                 android:text="@string/eight"
 45                 android:textSize="40sp" />
 46 
 47             <Button
 48                 android:id="@+id/nine"
 49                 android:layout_width="80dp"
 50                 android:layout_height="70dp"
 51                 android:layout_toRightOf="@id/eight"
 52                 android:text="@string/nine"
 53                 android:textSize="40sp" />
 54 
 55             <Button
 56                 android:id="@+id/add"
 57                 android:layout_width="80dp"
 58                 android:layout_height="70dp"
 59                 android:layout_alignParentRight="true"
 60                 android:layout_toRightOf="@id/nine"
 61                 android:text="@string/add"
 62                 android:textSize="40sp" />
 63 
 64             <Button
 65                 android:id="@+id/four"
 66                 android:layout_width="80dp"
 67                 android:layout_height="70dp"
 68                 android:layout_alignParentLeft="true"
 69                 android:layout_below="@id/seven"
 70                 android:text="@string/four"
 71                 android:textSize="40sp" />
 72 
 73             <Button
 74                 android:id="@+id/five"
 75                 android:layout_width="80dp"
 76                 android:layout_height="70dp"
 77                 android:layout_below="@id/eight"
 78                 android:layout_toRightOf="@id/four"
 79                 android:text="@string/five"
 80                 android:textSize="40sp" />
 81 
 82             <Button
 83                 android:id="@+id/six"
 84                 android:layout_width="80dp"
 85                 android:layout_height="70dp"
 86                 android:layout_below="@id/nine"
 87                 android:layout_toRightOf="@id/five"
 88                 android:text="@string/six"
 89                 android:textSize="40sp" />
 90 
 91             <Button
 92                 android:id="@+id/subtract"
 93                 android:layout_width="80dp"
 94                 android:layout_height="70dp"
 95                 android:layout_alignParentRight="true"
 96                 android:layout_below="@id/add"
 97                 android:layout_toRightOf="@id/six"
 98                 android:text="@string/subtract"
 99                 android:textSize="40sp" />
100 
101             <Button
102                 android:id="@+id/one"
103                 android:layout_width="80dp"
104                 android:layout_height="70dp"
105                 android:layout_alignParentLeft="true"
106                 android:layout_below="@id/four"
107                 android:text="@string/one"
108                 android:textSize="40sp" />
109 
110             <Button
111                 android:id="@+id/two"
112                 android:layout_width="80dp"
113                 android:layout_height="70dp"
114                 android:layout_below="@id/five"
115                 android:layout_toRightOf="@id/one"
116                 android:text="@string/two"
117                 android:textSize="40sp" />
118 
119             <Button
120                 android:id="@+id/three"
121                 android:layout_width="80dp"
122                 android:layout_height="70dp"
123                 android:layout_below="@id/six"
124                 android:layout_toRightOf="@id/two"
125                 android:text="@string/three"
126                 android:textSize="40sp" />
127 
128             <Button
129                 android:id="@+id/multiply"
130                 android:layout_width="80dp"
131                 android:layout_height="70dp"
132                 android:layout_alignParentRight="true"
133                 android:layout_below="@id/subtract"
134                 android:layout_toRightOf="@id/three"
135                 android:text="@string/multiply"
136                 android:textSize="40sp" />
137 
138             <Button
139                 android:id="@+id/zero"
140                 android:layout_width="80dp"
141                 android:layout_height="70dp"
142                 android:layout_alignParentLeft="true"
143                 android:layout_below="@id/one"
144                 android:text="@string/zero"
145                 android:textSize="40sp" />
146 
147             <Button
148                 android:id="@+id/clear"
149                 android:layout_width="80dp"
150                 android:layout_height="70dp"
151                 android:layout_below="@id/two"
152                 android:layout_toRightOf="@id/zero"
153                 android:text="@string/clear"
154                 android:textSize="40sp" />
155 
156             <Button
157                 android:id="@+id/result"
158                 android:layout_width="80dp"
159                 android:layout_height="70dp"
160                 android:layout_below="@id/three"
161                 android:layout_toRightOf="@id/clear"
162                 android:text="@string/result"
163                 android:textSize="40sp" />
164 
165             <Button
166                 android:id="@+id/divide"
167                 android:layout_width="80dp"
168                 android:layout_height="70dp"
169                 android:layout_alignParentRight="true"
170                 android:layout_below="@id/multiply"
171                 android:layout_toRightOf="@id/result"
172                 android:text="@string/divide"
173                 android:textSize="40sp" />
174 
175             <Button
176                 android:id="@+id/dot"
177                 android:layout_width="80dp"
178                 android:layout_height="70dp"
179                 android:layout_alignParentLeft="true"
180                 android:layout_below="@id/zero"
181                 android:text="@string/dot"
182                 android:textSize="40sp" />
183             <Button
184                 android:id="@+id/writeButton"
185                 android:layout_width="wrap_content"
186                 android:layout_height="wrap_content"
187                 android:layout_alignParentLeft="true"
188                 android:layout_below="@id/dot"
189                 android:text="@string/write"
190                 android:textSize="40sp" />
191             <Button
192                 android:id="@+id/readButton"
193                 android:layout_width="wrap_content"
194                 android:layout_height="wrap_content"
195                 android:layout_alignParentRight="true"
196                 android:layout_below="@id/dot"
197                 android:text="@string/read"
198                 android:textSize="40sp" />
199 
200             <CheckBox
201                 android:id="@+id/appendBox"
202                 android:text="@string/appendBox"
203                 android:layout_width="wrap_content"
204                 android:layout_height="wrap_content"
205                 android:layout_alignParentBottom="true"
206                 android:layout_toLeftOf="@+id/divide"
207                 android:layout_toStartOf="@+id/divide"
208                 android:layout_marginBottom="12dp"
209                 />
210 
211         </RelativeLayout>
212 
213         <EditText
214 
215             android:layout_width="match_parent"
216             android:layout_height="wrap_content"
217             android:id="@+id/textView" />
218 
219         <EditText
220 
221             android:layout_width="match_parent"
222             android:layout_height="wrap_content"
223             android:id="@+id/displayView" />
224 
225         <EditText
226             android:id="@+id/errorzero"
227             android:layout_width="fill_parent"
228             android:layout_height="wrap_content"
229             android:layout_gravity="center"
230             android:editable="false"
231             android:gravity="center"
232             />
233         <EditText
234             android:id="@+id/resultText"
235             android:layout_width="fill_parent"
236             android:layout_height="wrap_content"
237             android:layout_gravity="center"
238             android:editable="false"
239             android:gravity="left"
240             android:text="@string/resultText"
241             />
242     </LinearLayout>
243 </ScrollView>

View Code

事件监听和实现计算代码（写在MainActivity.java文件里）

  1 package com.example.lenovo.calculator;
  2 
  3 
  4 
  5         import android.app.Activity;
  6         import android.content.Context;
  7         import android.os.Bundle;
  8         import android.view.View;
  9         import android.view.View.OnClickListener;
 10         import android.widget.Button;
 11         import android.widget.CheckBox;
 12         import android.widget.EditText;
 13 
 14         import java.io.FileInputStream;
 15         import java.io.FileNotFoundException;
 16         import java.io.FileOutputStream;
 17         import java.io.IOException;
 18 
 19 public class MainActivity extends Activity {
 20     /**
 21      * Called when the activity is first created.
 22      */
 23     private EditText output = null;
 24     private EditText input = null;
 25     private Button btn0 = null;
 26     private Button btn1 = null;
 27     private Button btn2 = null;
 28     private Button btn3 = null;
 29     private Button btn4 = null;
 30     private Button btn5 = null;
 31     private Button btn6 = null;
 32     private Button btn7 = null;
 33     private Button btn8 = null;
 34     private Button btn9 = null;
 35     private Button btnadd = null;
 36     private Button btnsubtract = null;
 37     private Button btnmultiply = null;
 38     private Button btndivide = null;
 39     private Button btnclear = null;
 40     private Button btnresult = null;
 41     private Button btndot = null;
 42 
 43     private EditText errorzero = null;
 44 
 45     private EditText resultText = null;
 46     private Button writeButton = null;
 47     private Button readButton = null;
 48     private CheckBox appendBox = null;
 49     private EditText textView = null;
 50     private EditText displayView = null;
 51     public String FILE_NAME = "fileDemo.txt";
 52 
 53 
 54     private String str = "";//保存数字
 55     private String strold = "";//原数字
 56     private char act = \' \';//记录“加减乘除等于”符号
 57     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
 58     private Float result = null;//计算的输出结果
 59     private Boolean errBoolean = false;//有错误的时候为true，无错为false
 60     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
 61     private Boolean flagDot = false; //小数点标志位
 62 
 63 
 64 
 65     @Override
 66     public void onCreate(Bundle savedInstanceState) {
 67         super.onCreate(savedInstanceState);
 68         setContentView(R.layout.activity_main);
 69 
 70         output = (EditText) findViewById(R.id.output);
 71         input = (EditText) findViewById(R.id.input);
 72 
 73         errorzero = (EditText) findViewById(R.id.errorzero);
 74         resultText = (EditText) findViewById(R.id.resultText);
 75         writeButton = (Button) findViewById(R.id.writeButton);
 76         readButton = (Button) findViewById(R.id.readButton);
 77         textView = (EditText) findViewById(R.id.textView);
 78         displayView = (EditText) findViewById(R.id.displayView);
 79         appendBox = (CheckBox) findViewById(R.id.appendBox);
 80 
 81         btn0 = (Button) findViewById(R.id.zero);
 82         btn1 = (Button) findViewById(R.id.one);
 83         btn2 = (Button) findViewById(R.id.two);
 84         btn3 = (Button) findViewById(R.id.three);
 85         btn4 = (Button) findViewById(R.id.four);
 86         btn5 = (Button) findViewById(R.id.five);
 87         btn6 = (Button) findViewById(R.id.six);
 88         btn7 = (Button) findViewById(R.id.seven);
 89         btn8 = (Button) findViewById(R.id.eight);
 90         btn9 = (Button) findViewById(R.id.nine);
 91         btnadd = (Button) findViewById(R.id.add);
 92         btnsubtract = (Button) findViewById(R.id.subtract);
 93         btnmultiply = (Button) findViewById(R.id.multiply);
 94         btndivide = (Button) findViewById(R.id.divide);
 95         btnclear = (Button) findViewById(R.id.clear);
 96         btnresult = (Button) findViewById(R.id.result);
 97         btndot = (Button) findViewById(R.id.dot);
 98         //设置按钮侦听事件
 99         btn0.setOnClickListener(listener);
100         btn1.setOnClickListener(listener);
101         btn2.setOnClickListener(listener);
102         btn3.setOnClickListener(listener);
103         btn4.setOnClickListener(listener);
104         btn5.setOnClickListener(listener);
105         btn6.setOnClickListener(listener);
106         btn7.setOnClickListener(listener);
107         btn8.setOnClickListener(listener);
108         btn9.setOnClickListener(listener);
109         //执行运算
110         btnadd.setOnClickListener(listener);
111         btnsubtract.setOnClickListener(listener);
112         btnmultiply.setOnClickListener(listener);
113         btndivide.setOnClickListener(listener);
114         btnclear.setOnClickListener(listener);
115         btnresult.setOnClickListener(listener);
116 
117         btndot.setOnClickListener(listener);
118 
119         writeButton.setOnClickListener(writelistener);
120         readButton.setOnClickListener(readlistener);
121 
122 
123         // ATTENTION: This was auto-generated to implement the App Indexing API.
124         // See https://g.co/AppIndexing/AndroidStudio for more information.
125     }
126 
127 
128     private OnClickListener listener = new OnClickListener() {
129 
130         public void onClick(View v) {
131             // TODO Auto-generated method stub
132             switch (v.getId()) {
133                 //输入数字
134                 case R.id.zero:
135                     num(0);
136                     break;
137                 case R.id.one:
138                     num(1);
139                     break;
140                 case R.id.two:
141                     num(2);
142                     break;
143                 case R.id.three:
144                     num(3);
145                     break;
146                 case R.id.four:
147                     num(4);
148                     break;
149                 case R.id.five:
150                     num(5);
151                     break;
152                 case R.id.six:
153                     num(6);
154                     break;
155                 case R.id.seven:
156                     num(7);
157                     break;
158                 case R.id.eight:
159                     num(8);
160                     break;
161                 case R.id.nine:
162                     num(9);
163                     break;
164 
165                 case R.id.dot:
166                     dot();
167                     break;
168                 //执行运算
169                 case R.id.add:
170                     add();
171                     break;
172                 case R.id.subtract:
173                     sub();
174                     break;
175                 case R.id.multiply:
176                     multiply();
177                     break;
178                 case R.id.divide:
179                     divide();
180                     break;
181                 case R.id.clear:
182                     clear();
183                     break;
184                 //计算结果
185                 case R.id.result:
186                     result();
187                     if (!errBoolean && flagBoolean) {
188                         output.setText(String.valueOf(result));
189                     }
190                     resultText.setText(strold + act + str + "=" + result+"                          ");
191                     break;
192 
193                 default:
194                     break;
195 
196             }
197             input.setText(strold + act + str);
198             output.setText(String.valueOf(result));
199 
200 
201         }
202     };
203 
204     private OnClickListener writelistener = new OnClickListener() {
205         @Override
206         public void onClick(View view) {
207             //textView.setText("");
208 
209             FileOutputStream fos = null;
210             try {
211                 if (appendBox.isChecked()) {
212                     fos = openFileOutput(FILE_NAME, Context.MODE_APPEND);
213                 } else {
214                     fos = openFileOutput(FILE_NAME, Context.MODE_PRIVATE);
215                 }
216                 String text = resultText.getText().toString();
217                 fos.write(text.getBytes());
218                 textView.setText("文件写入成功，写入长度：" + text.length());
219                 //resultText.setText("");
220 
221             } catch (FileNotFoundException e) {
222                 e.printStackTrace();
223             } catch (IOException e) {
224                 e.printStackTrace();
225             }
226             finally {
227                 if (fos != null)
228                     try {
229                         fos.flush();
230                         fos.close();
231                     } catch (IOException e) {
232                         e.printStackTrace();
233                     }
234             }
235         }
236     };
237     private OnClickListener readlistener = new OnClickListener() {
238         @Override
239         public void onClick(View view) {
240 
241             displayView.setText("");
242             FileInputStream fis = null;
243             try {
244                 fis = openFileInput(FILE_NAME);
245                 if (fis.available() == 0) {
246                     return;
247                 }
248                 byte[] readBytes = new byte[fis.available()];
249                 while (fis.read(readBytes) != -1) {
250 
251                 }
252                 String text = new String(readBytes);
253                 displayView.setText(text);
254                 textView.setText("文件读取成功，写入长度：" + text.length());
255 
256             } catch (FileNotFoundException e) {
257                 e.printStackTrace();
258             } catch (IOException e) {
259                 e.printStackTrace();
260             }
261 
262         }
263     };
264 
265     private void dot() {
266         // TODO Auto-generated method stub
267 
268         if (!flagDot) {
269             str = str + ".";
270             flagBoolean = false;
271             flagDot = true;
272         }
273     }
274 
275     private void clear() {
276         // TODO Auto-generated method stub
277         str = strold = "";
278         count = 0;
279         act = \' \';
280         result = null;
281         flagBoolean = false;
282         flagDot = false;
283         input.setText(strold + act + str);
284         output.setText("");
285         errorzero.setText("");
286         displayView.setText("");
287         textView.setText("");
288         resultText.setText("");
289     }
290 
291     private void divide() {
292         // TODO Auto-generated method stub
293         if (flagBoolean) {
294             check();
295             act = \'/\';
296             flagBoolean = false;
297         }
298     }
299 
300     private void multiply() {
301         // TODO Auto-generated method stub
302         if (flagBoolean) {
303             check();
304             act = \'*\';
305             flagBoolean = false;
306         }
307     }
308 
309     private void sub() {
310         // TODO Auto-generated method stub
311         if (flagBoolean) {
312             check();
313             act = \'-\';
314             flagBoolean = false;
315         }
316     }
317 
318     private void add() {
319         // TODO Auto-generated method stub
320         if (flagBoolean) {
321             check();
322             act = \'+\';
323             flagBoolean = false;
324         }
325     }
326 
327     private void check() {
328         // TODO Auto-generated method stub
329         if (count >= 1) {
330             result();
331             str = String.valueOf(result);
332         }
333         strold = str;
334         str = "";
335         count++;
336         flagDot = false;
337         errorzero.setText("");
338     }
339 
340     //计算输出结果
341     private void result() {
342         // TODO Auto-generated method stub
343         if (flagBoolean) {
344             Float a, b;
345 
346             a = Float.parseFloat(strold);
347             b = Float.parseFloat(str);
348 
349             if (b == 0 && act == \'/\') {
350                 clear();
351                 errorzero.setText("除数不能为零!");
352                 //output.setText("除数不能为零!");
353 
354 
355                 //errBoolean=true;
356             }
357 
358 
359             if (!errBoolean) {
360                 switch (act) {
361                     case \'+\':
362                         result = a + b;
363                         break;
364                     case \'-\':
365                         result = a - b;
366                         break;
367                     case \'*\':
368                         result = a * b;
369                         break;
370                     case \'/\':
371                         result = a / b;
372                         break;
373 
374                     default:
375                         break;
376                 }
377             }
378 
379 
380         }
381     }
382 
383     private void num(int i) {
384         // TODO Auto-generated method stub
385         str = str + String.valueOf(i);
386         flagBoolean = true;
387         errorzero.setText("");
388     }
389 
390 }

View Code

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：

 1 <resources>
 2     <string name="app_name">Calculator</string>
 3     <string name="action_settings">Settings</string>
 4         <string name="zero">0</string>
 5         <string name="one">1</string>
 6         <string name="two">2</string>
 7         <string name="three">3</string>
 8         <string name="four">4</string>
 9         <string name="five">5</string>
10         <string name="six">6</string>
11         <string name="seven">7</string>
12         <string name="eight">8</string>
13         <string name="nine">9</string>
14         <string name="add">+</string>
15         <string name="subtract">-</string>
16         <string name="multiply">*</string>
17         <string name="divide">/</string>
18         <string name="clear">CE</string>
19         <string name="result">=</string>
20         <string name="shuru">请按数字键盘输入数字</string>
21         <string name="shuchu">计算器输出结果</string>
22         <string name="dot">.</string>
23         <string name="write">写入</string>
24         <string name="read">读取</string>
25         <string name="resultText">计算式</string>
26         <string name="appendBox">追加模式</string>
27 
28 </resources>

View Code

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

秒客网

制作一个简易计算器——基于Android Studio实现

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