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

效果为输入了10个字符后，光标停在末尾