方法一：

在 xml 檔案中設定文字編輯框屬性作字元數限制

如：android:maxLength="10" 即限制最大輸入字元個數為10

方法二：

在程式碼中使用InputFilter 進行過濾

//editText.setFilters(new InputFilter[]{new InputFilter.LengthFilter(20)}); 即限定最大輸入字元數為20

1. publicclass TextEditActivity extends Activity { 
2.     /** Called when the activity is first created. */
3.     @Override
4.     publicvoid onCreate(Bundle savedInstanceState) { 
5.         super.onCreate(savedInstanceState); 
6.         setContentView(R.layout.main); 
7.         EditText editText = (EditText)findViewById(R.id.entry); 
8.         editText.setFilters(new InputFilter[]{new InputFilter.LengthFilter(20)}); 
9.     } 
10. } 

public class TextEditActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        EditText editText = (EditText)findViewById(R.id.entry);
        editText.setFilters(new InputFilter[]{new InputFilter.LengthFilter(20)});
    }
}
 

方法三：

利用 TextWatcher 進行監聽

1. package cie.textEdit; 
2. import android.text.Editable; 
3. import android.text.Selection; 
4. import android.text.TextWatcher; 
5. import android.widget.EditText; 
6. /*
7. * 監聽輸入內容是否超出最大長度，並設定游標位置
8. * */
9. publicclass MaxLengthWatcher implements TextWatcher { 
10.     privateint maxLen = 0; 
11.     private
     EditText editText = null; 
12.     public MaxLengthWatcher(int maxLen, EditText editText) { 
13.         this.maxLen = maxLen; 
14.         this.editText = editText; 
15.     } 
16.     publicvoid afterTextChanged(Editable arg0) { 
17.         // TODO Auto-generated method stub
18.     } 
19.     publicvoid beforeTextChanged(CharSequence arg0, int arg1, int arg2, 
20.             int arg3) { 
21.         // TODO Auto-generated method stub
22.     } 
23.     publicvoid onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { 
24.         // TODO Auto-generated method stub
25.         Editable editable = editText.getText(); 
26.         int len = editable.length(); 
27.         if(len > maxLen) 
28.         { 
29.             int selEndIndex = Selection.getSelectionEnd(editable); 
30.             String str = editable.toString(); 
31.             //擷取新字串
32.             String newStr = str.substring(0,maxLen); 
33.             editText.setText(newStr); 
34.             editable = editText.getText(); 
35.             //新字串的長度
36.             int newLen = editable.length(); 
37.             //舊游標位置超過字串長度
38.             if(selEndIndex > newLen) 
39.             { 
40.                 selEndIndex = editable.length(); 
41.             } 
42.             //設定新游標所在的位置
43.             Selection.setSelection(editable, selEndIndex); 
44.         } 
45.     } 
46. } 

package cie.textEdit;

import android.text.Editable;
import android.text.Selection;
import android.text.TextWatcher;
import android.widget.EditText;

/*
 * 監聽輸入內容是否超出最大長度，並設定游標位置
 * */
public class MaxLengthWatcher implements TextWatcher {

	private int maxLen = 0;
	private EditText editText = null;
	
	
	public MaxLengthWatcher(int maxLen, EditText editText) {
		this.maxLen = maxLen;
		this.editText = editText;
	}

	public void afterTextChanged(Editable arg0) {
		// TODO Auto-generated method stub
		
	}

	public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
			int arg3) {
		// TODO Auto-generated method stub
		
	}

	public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
		// TODO Auto-generated method stub
		Editable editable = editText.getText();
		int len = editable.length();
		
		if(len > maxLen)
		{
			int selEndIndex = Selection.getSelectionEnd(editable);
			String str = editable.toString();
			//擷取新字串
			String newStr = str.substring(0,maxLen);
			editText.setText(newStr);
			editable = editText.getText();
			
			//新字串的長度
			int newLen = editable.length();
			//舊游標位置超過字串長度
			if(selEndIndex > newLen)
			{
				selEndIndex = editable.length();
			}
			//設定新游標所在的位置
			Selection.setSelection(editable, selEndIndex);
			
		}
	}

}

對應的 activity 部分的呼叫為：

1. package cie.textEdit; 
2. import android.app.Activity; 
3. import android.os.Bundle; 
4. import android.text.InputFilter; 
5. import android.widget.EditText; 
6. publicclass TextEditActivity extends Activity { 
7.     /** Called when the activity is first created. */
8.     @Override
9.     publicvoid onCreate(Bundle savedInstanceState) { 
10.         super.onCreate(savedInstanceState); 
11.         setContentView(R.layout.main); 
12.         EditText editText = (EditText) findViewById(R.id.entry); 
13.         editText.addTextChangedListener(new MaxLengthWatcher(10, editText)); 
14.     } 
15. } 

package cie.textEdit;

import android.app.Activity;
import android.os.Bundle;
import android.text.InputFilter;
import android.widget.EditText;

public class TextEditActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

		EditText editText = (EditText) findViewById(R.id.entry);
		editText.addTextChangedListener(new MaxLengthWatcher(10, editText));

    }
}

限制輸入字元數為10個

main.xml 檔案

1. <?xmlversion="1.0"encoding="utf-8"?>
2. <RelativeLayoutxmlns:android="http://schemas.android.com/apk/res/android"
3.     android:layout_width="fill_parent"
4.     android:layout_height="fill_parent">
5.     <TextView
6.         android:id="@+id/label"
7.         android:layout_width="fill_parent"
8.         android:layout_height="wrap_content"
9.         android:text="Type here:"/>
10.     <EditText
11.         android:id="@+id/entry"
12.         android:singleLine="true"
13.         android:layout_width="fill_parent"
14.         android:layout_height="wrap_content"
15.         android:background="@android:drawable/editbox_background"
16.         android:layout_below="@id/label"/>
17.     <Button
18.         android:id="@+id/ok"
19.         android:layout_width="wrap_content"
20.         android:layout_height="wrap_content"
21.         android:layout_below="@id/entry"
22.         android:layout_alignParentRight="true"
23.         android:layout_marginLeft="10dip"
24.         android:text="OK"/>
25.     <Button
26.         android:layout_width="wrap_content"
27.         android:layout_height="wrap_content"
28.         android:layout_toLeftOf="@id/ok"
29.         android:layout_alignTop="@id/ok"
30.         android:text="Cancel"/>
31. </RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView
        android:id="@+id/label"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Type here:"/>
    <EditText
        android:id="@+id/entry"
        android:singleLine="true"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@android:drawable/editbox_background"
        android:layout_below="@id/label"/>
    <Button
        android:id="@+id/ok"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/entry"
        android:layout_alignParentRight="true"
        android:layout_marginLeft="10dip"
        android:text="OK" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/ok"
        android:layout_alignTop="@id/ok"
        android:text="Cancel" />
</RelativeLayout>

效果為輸入了10個字元後，游標停在末尾