不良代码展示-很多判断的写法-给新手

原创文章，如有转载，请注明出处：http://blog.csdn.net/yihui823/article/details/6801695

今天Review代码，看到了一串很“漂亮”的代码。这里把代码改了一下，贴给新手们，作为一个教训吧。
漂亮的意思，是有很工整的缩进。

[java] view plaincopy

1. package com.hoperun;  
2.   
3. import android.view.View;  
4. import android.view.View.OnClickListener;  
5.   
6. /** 
7.  * 数字键盘监听器 
8.  */  
9. public class NumListener  implements OnClickListener {  
10.   
11.     public void onClick(View v) {  
12.   
13.         if (v.equals(btnNum0)) {  
14.             //按键0  
15.         } else {   
16.             if (v.equals(btnNum1)) {  
17.                 //按键1  
18.             } else {  
19.                 if (v.equals(btnNum2)) {  
20.                     //按键2  
21.                 } else {  
22.                     if (v.equals(btnNum3)) {  
23.                         //按键3  
24.                     } else {  
25.                         if (v.equals(btnNum4)) {  
26.                             //按键4  
27.                         } else {  
28.                             if (v.equals(btnNum5)) {  
29.                                 //按键5  
30.                             } else {  
31.                                 if (v.equals(btnNum6)) {  
32.                                     //按键6  
33.                                 } else {  
34.                                     if (v.equals(btnNum7)) {  
35.                                         //按键7  
36.                                     } else {  
37.                                         if (v.equals(btnNum8)) {  
38.                                             //按键8  
39.                                         } else {  
40.                                             if (v.equals(btnNum9)) {  
41.                                                 //按键9  
42.                                             } else {  
43.                                                 if (v.equals(btnNumAdd)) {  
44.                                                     //按键加法  
45.                                                 } else {  
46.                                                     if (v.equals(btnNumSubtraction)) {  
47.                                                         //按键减法  
48.                                                     } else {  
49.                                                         if (v.equals(btnNumEquals)) {  
50.                                                             //按键等于  
51.                                                         }  
52.                                                     }  
53.                                                 }  
54.                                             }  
55.                                         }  
56.                                     }  
57.                                 }  
58.                             }  
59.                         }  
60.                     }  
61.                 }  
62.             }  
63.         }   
64.           
65.           
66.     }  
67.   
68. }  

其实，这么写是完全没有必要的。这么多的else，其实可以叠在else if里面，如下：

[java] view plaincopy

1. package com.hoperun;  
2.   
3. import android.view.View;  
4. import android.view.View.OnClickListener;  
5.   
6. /** 
7.  * 数字键盘监听器 
8.  */  
9. public class NumListener  implements OnClickListener {  
10.   
11.     public void onClick(View v) {  
12.   
13.         if (v.equals(btnNum0)) {  
14.             //按键0  
15.         } else { if (v.equals(btnNum1)) {  
16.             //按键1  
17.         } else if (v.equals(btnNum2)) {  
18.             //按键2  
19.         } else if (v.equals(btnNum3)) {  
20.             //按键3  
21.         } else if (v.equals(btnNum4)) {  
22.             //按键4  
23.         } else if (v.equals(btnNum5)) {  
24.             //按键5  
25.         } else if (v.equals(btnNum6)) {  
26.             //按键6  
27.         } else if (v.equals(btnNum7)) {  
28.             //按键7  
29.         } else if (v.equals(btnNum8)) {  
30.             //按键8  
31.         } else if (v.equals(btnNum9)) {  
32.             //按键9  
33.         } else if (v.equals(btnNumAdd)) {  
34.             //按键加法  
35.         } else if (v.equals(btnNumSubtraction)) {  
36.             //按键减法  
37.         } else if (v.equals(btnNumEquals)) {  
38.             //按键等于  
39.         }  
40.           
41.     }  
42.   
43. }  

其实这个效率不高。其实传入的参数View，就是被按住的那个按钮，不需要用equals判断，直接用“ == ”来判断就可以了。

当然，最好的还不是用“ == ”，而是用switch - case.

[java] view plaincopy

1. package com.hoperun;  
2.   
3. import android.view.View;  
4. import android.view.View.OnClickListener;  
5.   
6. /** 
7.  * 数字键盘监听器 
8.  */  
9. public class NumListener  implements OnClickListener {  
10.   
11.     public void onClick(View v) {  
12.   
13.         switch (v.getId()) {  
14.             case R.id.key_0:  
15.                 //按键0  
16.                 break;  
17.             case R.id.key_1:  
18.                 //按键1  
19.                 break;  
20.             case R.id.key_2:  
21.                 //按键2  
22.                 break;  
23.             case R.id.key_3:  
24.                 //按键3  
25.                 break;  
26.             case R.id.key_4:  
27.                 //按键4  
28.                 break;  
29.             case R.id.key_5:  
30.                 //按键0  
31.                 break;  
32.             case R.id.key_6:  
33.                 //按键6  
34.                 break;  
35.             case R.id.key_7:  
36.                 //按键7  
37.                 break;  
38.             case R.id.key_8:  
39.                 //按键8  
40.                 break;  
41.         }  
42.     }  
43.   
44. }  

仅给新人学习，高手勿喷。