Android TextWatcher监控EditText中的输入内容并限制其输入字符个数

      布局中EditText在android布局中经常用到，对EditText中输入的内容也经常需要进行限制，我们可以通过TextWatcher去观察输入框中输入的内容，作个笔记。

主布局：

xml version="1.0" encoding="utf-8" ?>
< LinearLayout xmlns:android ="http://schemas.android.com/apk/res/android"
android:orientation ="vertical"
android:layout_width ="fill_parent"
android:layout_height ="fill_parent"
>
< TextView android:id ="@+id/tv"
android:layout_width ="fill_parent"
android:layout_height ="wrap_content"
android:textColor ="@android:color/white"
android:ellipsize ="marquee"
android:focusable ="true"
android:marqueeRepeatLimit ="marquee_forever"
android:focusableInTouchMode ="true"
android:scrollHorizontally ="true"
android:text ="Please input the text:"
/>
< EditText android:id ="@+id/ET"
android:layout_width ="match_parent"
android:layout_height ="wrap_content"
android:inputType ="number" />
LinearLayout >

java代码：

package com.android.text;

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.TextView;
import android.widget.Toast;

public class TextWatcherDemo extends Activity {
private TextView mTextView;
private EditText mEditText;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
setContentView(R.layout.main);
mTextView = (TextView)findViewById(R.id.tv);
mEditText = (EditText)findViewById(R.id.ET);
mEditText.addTextChangedListener(mTextWatcher);
}
TextWatcher mTextWatcher = new TextWatcher() {
private CharSequence temp;
private int editStart ;
private int editEnd ;
@Override
public void beforeTextChanged(CharSequence s, int arg1, int arg2,
int arg3) {
temp = s;
}

@Override
public void onTextChanged(CharSequence s, int arg1, int arg2,
int arg3) {
mTextView.setText(s);
}

@Override
public void afterTextChanged(Editable s) {
editStart = mEditText.getSelectionStart();
editEnd = mEditText.getSelectionEnd();
if (temp.length() > 10 ) {
Toast.makeText(TextWatcherDemo. this ,
" 你输入的字数已经超过了限制！ " , Toast.LENGTH_SHORT)
.show();
s.delete(editStart - 1 , editEnd);
int tempSelection = editStart;
mEditText.setText(s);
mEditText.setSelection(tempSelection);
}
}
};
}

转载于:https://www.cnblogs.com/cat-fang/archive/2011/04/12/2013428.html