Android开发教程：监听EditText的变化

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本文介绍如何在Android应用中监听EditText控件的文字变化，并通过实例演示了如何限制EditText输入内容的长度及验证输入是否为整数。

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监听EditText的变化

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：

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。

MainActivity.java
1.package com.lingdududu.watcher;

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.

12.public class MainActivity extends Activity {

13. private EditText text;

14. String str;

15. @Override

16. public void onCreate(Bundle savedInstanceState) {

17. super.onCreate(savedInstanceState);

18. setContentView(R.layout.main);

19.

20. text = (EditText)findViewById(R.id.text);

21. text.addTextChangedListener(textWatcher);

22. }

23.

24. private TextWatcher textWatcher = new TextWatcher() {

25.

26. @Override

27. public void afterTextChanged(Editable s) {

28. // TODO Auto-generated method stub

29. Log.d("TAG","afterTextChanged--------------->");

30. }

31.

32. @Override

33. public void beforeTextChanged(CharSequence s, int start, int count,

34. int after) {

35. // TODO Auto-generated method stub

36. Log.d("TAG","beforeTextChanged--------------->");

37. }

38.

39. @Override

40. public void onTextChanged(CharSequence s, int start, int before,

41. int count) {

42. Log.d("TAG","onTextChanged--------------->");

43. str = text.getText().toString();

44. try {

45. //if ((heighText.getText().toString())!=null)

46. Integer.parseInt(str);

47.

48. } catch (Exception e) {

49. // TODO: handle exception

50. showDialog();

51. }

52.

53. }

54. };

55.

56. private void showDialog(){

57. AlertDialog dialog;

58. AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);

59. builder.setTitle("消息").setIcon(android.R.drawable.stat_notify_error);

60. builder.setMessage("你输出的整型数字有误，请改正");

61. builder.setPositiveButton("确定", new DialogInterface.OnClickListener(){

62. @Override

63. public void onClick(DialogInterface dialog, int which) {

64. // TODO Auto-generated method stub

65.

66. }

67. });

68. dialog = builder.create();

69. dialog.show();

70. }

71.}
main.xml
1.<?xml version="1.0" encoding="utf-8"?>

2.<LinearLayout xmlns: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. >

7.<TextView

8. android:layout_width="fill_parent"

9. android:layout_height="wrap_content"

10. android:text="请输入整型数字"

11. />

12.<EditText

13. android:id="@+id/text"

14. android:layout_width="fill_parent"

15. android:layout_height="wrap_content"

16. />

17.</LinearLayout>
效果图：

当我们在输入框输入不是整型数字的时候，会立刻弹出输入框，提示你改正

本篇文章来源于 Linux公社网站(www.linuxidc.com) 原文链接：http://www.linuxidc.com/Linux/2012-01/52648.htm

新历史版本 :Android---3种方式限制EditView输入字数

方法一：利用TextWatcher

editText.addTextChangedListener(new TextWatcher() {
           private CharSequence temp;
           private boolean isEdit = true;
           private int selectionStart ;
           private int selectionEnd ;
           @Override
           public void beforeTextChanged(CharSequence s, int arg1, int arg2,
                   int arg3) {
               temp = s;
           }

           @Override
           public void onTextChanged(CharSequence s, int arg1, int arg2,
                   int arg3) {
           }

           @Override
           public void afterTextChanged(Editable s) {
                selectionStart = editText.getSelectionStart();
               selectionEnd = editText.getSelectionEnd();
               Log.i("gongbiao1",""+selectionStart);
               if (temp.length() > Constant.TEXT_MAX) {
                   Toast.makeText(KaguHomeActivity.this,
                           R.string.edit_content_limit, Toast.LENGTH_SHORT)
                           .show();
                   s.delete(selectionStart-1, selectionEnd);
                   int tempSelection = selectionStart;
                   editText.setText(s);
                   editText.setSelection(tempSelection);
               }
           }

       });

editText.addTextChangedListener(new TextWatcher() {
            private CharSequence temp;
            private boolean isEdit = true;
            private int selectionStart ;
            private int selectionEnd ;
            @Override
            public void beforeTextChanged(CharSequence s, int arg1, int arg2,
                    int arg3) {
                temp = s;
            }

            @Override
            public void onTextChanged(CharSequence s, int arg1, int arg2,
                    int arg3) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                 selectionStart = editText.getSelectionStart();
                selectionEnd = editText.getSelectionEnd();
                Log.i("gongbiao1",""+selectionStart);
                if (temp.length() > Constant.TEXT_MAX) {
                    Toast.makeText(KaguHomeActivity.this,
                            R.string.edit_content_limit, Toast.LENGTH_SHORT)
                            .show();
                    s.delete(selectionStart-1, selectionEnd);
                    int tempSelection = selectionStart;
                    editText.setText(s);
                    editText.setSelection(tempSelection);
                }
            }