Android TextWatcher監控EditText中的輸入內容並限制其輸入字元個數

布局中EditText在android布局中經常用到，對EditText中輸入的內容也經常需要進行限制，我們可以通過TextWatcher去觀察輸入框中輸入的內容，作個筆記。

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代碼：

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,                        "你輸入的字數已經超過了限制！", Toast.LENGTH_SHORT)                        .show();                s.delete(editStart-1, editEnd);                int tempSelection = editStart;                mEditText.setText(s);                mEditText.setSelection(tempSelection);            }        }    };}