android 监听EditText 的变化

妖狐艹你老母 2022-05-31 01:46 390阅读 0赞

使用EditText的addTextChangedListener(TextWatcher watcher)方法对EditText实现监听，TextWatcher是一个接口类，所以必须实现TextWatcher里的抽象方法：  
![20150622165457502][]  
 当EditText里面的内容有变化的时候，触发TextChangedListener事件，就会调用TextWatcher里面的抽象方法。  
布局：

**\[html\]** [view plain][] [copy][view plain]

1.  <?xmlversion="1.0"encoding="utf-8"?>
2.  <LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
3.  android:orientation="vertical"
4.  android:layout\_width="fill\_parent"
5.  android:layout\_height="fill\_parent">
6.  <EditText
7.  android:id="@+id/main\_et"
8.  android:layout\_width="fill\_parent"
9.  android:layout\_height="wrap\_content"/>
10. <TextView
11. android:id="@+id/main\_tv"
12. android:layout\_width="fill\_parent"
13. android:layout\_height="wrap\_content"/>
14. </LinearLayout>

一、实现监听文本框字数，提示还能输入多少个字符  
MainActivity：

**\[java\]** [view plain][] [copy][view plain]

1.  package chay.mian; 
2.  
3.  import android.app.Activity; 
4.  import android.os.Bundle; 
5.  import android.text.Editable; 
6.  import android.text.TextWatcher; 
7.  import android.view.View; 
8.  import android.widget.EditText; 
9.  import android.widget.TextView; 
10. 
11. publicclass MainActivity extends Activity \{ 
12. 
13. private EditText editText; 
14. private TextView tip; 
15. privatefinalint charMaxNum = 10; // 允许输入的字数
16. 
17. @Override
18. protectedvoid onCreate(Bundle savedInstanceState) \{ 
19. super.onCreate(savedInstanceState); 
20.  setContentView(R.layout.activity\_main); 
21.  init(); 
22.  \} 
23. 
24. privatevoid init() \{ 
25.  editText = (EditText) findViewById(R.id.main\_et); 
26.  editText.addTextChangedListener(new EditChangedListener()); 
27. 
28.  tip = (TextView) findViewById(R.id.main\_tv); 
29.  tip.setText("0/"\+charMaxNum); 
30.  \} 
31. 
32. class EditChangedListener implements TextWatcher \{ 
33. private CharSequence temp; // 监听前的文本
34. privateint editStart; // 光标开始位置
35. privateint editEnd; // 光标结束位置
36. 
37. // 输入文本之前的状态
38. @Override
39. publicvoid beforeTextChanged(CharSequence s, int start, int count,int after) \{ 
40.  temp = s; 
41.  \} 
42. 
43. // 输入文字中的状态，count是一次性输入字符数
44. @Override
45. publicvoid onTextChanged(CharSequence s, int start, int before, int count) \{ 
46. // if (charMaxNum - s.length() <= 5) \{ 
47. // tip.setText("还能输入" + (charMaxNum - s.length()) + "字符");
48. // \}
49.  tip.setText((s.length()) + "/" \+ charMaxNum); 
50.  \} 
51. 
52. // 输入文字后的状态
53. @Override
54. publicvoid afterTextChanged(Editable s) \{ 
55. /\*\* 得到光标开始和结束位置 ,超过最大数后记录刚超出的数字索引进行控制 \*/
56.  editStart = editText.getSelectionStart(); 
57.  editEnd = editText.getSelectionEnd(); 
58. if (temp.length() > charMaxNum) \{ 
59. // Toast.makeText(getApplicationContext(), "最多输入10个字符", Toast.LENGTH\_SHORT).show();
60.  s.delete(editStart - 1, editEnd); 
61.  editText.setText(s); 
62.  editText.setSelection(s.length()); 
63.  \} 
64.  \} 
65.  \}; 
66. \}

![20150622171358260][]

二、数据类型检验，当输入不是整型数字的时候，会立刻弹出输入框，提示改正  
MainActivity：

**\[java\]** [view plain][] [copy][view plain]

1.  package chay.mian; 
2.  
3.  import android.app.Activity; 
4.  import android.app.AlertDialog; 
5.  import android.content.DialogInterface; 
6.  import android.os.Bundle; 
7.  import android.text.Editable; 
8.  import android.text.TextWatcher; 
9.  import android.util.Log; 
10. import android.widget.EditText; 
11. import android.widget.TextView; 
12. 
13. publicclass MainActivity extends Activity \{ 
14. 
15. private EditText editText; 
16. private TextView tip; 
17.  String str; 
18. 
19. @Override
20. protectedvoid onCreate(Bundle savedInstanceState) \{ 
21. super.onCreate(savedInstanceState); 
22.  setContentView(R.layout.activity\_mian); 
23.  init(); 
24.  \} 
25. 
26. privatevoid init() \{ 
27.  editText = (EditText) findViewById(R.id.mian\_et); 
28.  editText.addTextChangedListener(new EditChangedListener()); 
29.  tip = (TextView) findViewById(R.id.mian\_tv); 
30.  tip.setText("请输入整型数字"); 
31.  \} 
32. 
33. class EditChangedListener implements TextWatcher \{ 
34. 
35. // 输入文本之前的状态
36. @Override
37. publicvoid beforeTextChanged(CharSequence s, int start, int count, int after) \{ 
38.  Log.d("TAG", "beforeTextChanged--------------->"); 
39.  \} 
40. 
41. // 输入文字中的状态，count是一次性输入字符数
42. @Override
43. publicvoid onTextChanged(CharSequence s, int start, int before, int count) \{ 
44.  Log.d("TAG", "onTextChanged--------------->"); 
45.  \} 
46. 
47. // 输入文字后的状态
48. @Override
49. publicvoid afterTextChanged(Editable s) \{ 
50.  Log.d("TAG", "afterTextChanged--------------->"); 
51.  str = editText.getText().toString(); 
52. try \{ 
53. // if ((editText.getText().toString()) != null)
54.  Integer.parseInt(str); 
55.  \} catch (Exception e) \{ 
56.  showDialog(); 
57.  \} 
58.  \} 
59.  \}; 
60. 
61. privatevoid showDialog() \{ 
62.  AlertDialog dialog; 
63.  AlertDialog.Builder builder = new AlertDialog.Builder(this); 
64.  builder.setTitle("消息").setIcon(android.R.drawable.stat\_notify\_error); 
65.  builder.setMessage("你输出的整型数字有误，请改正"); 
66.  builder.setPositiveButton("确定", new DialogInterface.OnClickListener() \{ 
67. @Override
68. publicvoid onClick(DialogInterface dialog, int which) \{ 
69. // TODO Auto-generated method stub
70.  \} 
71.  \}); 
72.  dialog = builder.create(); 
73.  dialog.show(); 
74.  \} 
75. \}

![20150622175126611][]

在LogCat查看调用这些方法的顺序：  
beforeTextChanged-->onTextChanged-->onTextChanged  
![20150622175205132][]

欢迎交流 http://blog.csdn.net/ycwol/article/details/46594275

[20150622165457502]: /images/20220531/341dca69253a4e66bf773a29d000e2eb.png
[view plain]: http://blog.csdn.net/ycwol/article/details/46594275#
[20150622171358260]: /images/20220531/2aa02beef81d46e6b9a85b86b667bfeb.png
[20150622175126611]: /images/20220531/9721d7ca252c40dd9dd8a9a1246354b6.png
[20150622175205132]: /images/20220531/74f44ea40dcb4ceda502553ed32ae3a1.png