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