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

 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
  * */
 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;

 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

 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

方法四：

基本思路同方法三，监听 EditText 当中输入字符串的长度，如果超长，给出提示。

 package cie.textEdit;

 import android.app.Activity;
 import android.os.Bundle;
 import android.text.Editable;
 import android.text.TextWatcher;
 import android.util.Log;
 import android.widget.EditText;
 import android.widget.Toast;

 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);

         final EditText editText = (EditText)findViewById(R.id.entry);
         editText.addTextChangedListener(new TextWatcher(){
             private int selectionStart = 0;
             private int selectionEnd = 0;
             private CharSequence temp = null;

             public void afterTextChanged(Editable arg0) {
                 // TODO Auto-generated method stub
                 selectionStart = editText.getSelectionStart();
                 selectionEnd = editText.getSelectionEnd();
                 Log.i(myConstant.Tag,"selectionStart" + selectionStart);
                 if(temp.length() > myConstant.TextMaxLen)
                 {
                     Toast.makeText(TextEditActivity.this, R.string.string_limit, Toast.LENGTH_SHORT).show();
                     arg0.delete(selectionStart-1, selectionEnd);
                     int tempSelection = selectionStart;
                     editText.setText(arg0);
                     editText.setSelection(tempSelection);
                 }
             }

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

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

             }

         });
     }
 }

当文本输入字符数10个，再输入字符时，就会出现