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); } } };}

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