android 中如何限制 EditText 最大输入字符数

方法一：

在 xml 文件中设置文本编辑框属性作字符数限制

如：android:maxLength="10" 即限制最大输入字符个数为10

 

方法二：

在代码中使用InputFilter 进行过滤

//editText.setFilters(new InputFilter[]{new InputFilter.LengthFilter(20)}); 即限定最大输入字符数为20

 

 

 publicclass TextEditActivity extends Activity {
     /** Called when the activity is first created. */
     @Override
     publicvoid 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)});
     }
 }

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 进行监听

 

 package cie.textEdit;

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

 /*
 * 监听输入内容是否超出最大长度，并设置光标位置
 * */
 publicclass MaxLengthWatcher implements TextWatcher {

     privateint maxLen = 0;
     private EditText editText = null;


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

     publicvoid afterTextChanged(Editable arg0) {
         // TODO Auto-generated method stub

     }

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

     }

     publicvoid 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();
             //截取新字符串
             String newStr = str.substring(0,maxLen);
             editText.setText(newStr);
             editable = editText.getText();

             //新字符串的长度
             int newLen = editable.length();
             //旧光标位置超过字符串长度
             if(selEndIndex > newLen)
             {
                 selEndIndex = editable.length();
             }
             //设置新光标所在的位置
             Selection.setSelection(editable, selEndIndex);

         }
     }

 }

package cie.textEdit;

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

/*
 * 监听输入内容是否超出最大长度，并设置光标位置
 * */
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();
			//截取新字符串
			String newStr = str.substring(0,maxLen);
			editText.setText(newStr);
			editable = editText.getText();
			
			//新字符串的长度
			int newLen = editable.length();
			//旧光标位置超过字符串长度
			if(selEndIndex > newLen)
			{
				selEndIndex = editable.length();
			}
			//设置新光标所在的位置
			Selection.setSelection(editable, selEndIndex);
			
		}
	}

}

对应的 activity 部分的调用为：

 

 

 package cie.textEdit;

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

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

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

     }
 }

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));

    }
}

限制输入字符数为10个

 

main.xml 文件

 

 <?xmlversion="1.0"encoding="utf-8"?>
 <RelativeLayoutxmlns: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>

<?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>

效果为输入了10个字符后，光标停在末尾