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); } } }; }