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>
- 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 }
二、细节
仅仅将主干部分代码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>
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
时间： 2025-01-05 00:39:12