android 監聽EditText 的變化

標籤：android   edittext   

使用EditText的addTextChangedListener(TextWatcher watcher)方法對EditText實現監聽，TextWatcher是一個介面類，所以必須實現TextWatcher裡的抽象方法：

當EditText裡面的內容有變化的時候，觸發TextChangedListener事件，就會調用TextWatcher裡面的抽象方法。
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" ><EditText    android:id="@+id/main_et"     android:layout_width="fill_parent"       android:layout_height="wrap_content" /> <TextView    android:id="@+id/main_tv"     android:layout_width="fill_parent"       android:layout_height="wrap_content" /> </LinearLayout>

一、實現監聽文字框字數，提示還能輸入多少個字元
MainActivity：

package chay.mian;import android.app.Activity;import android.os.Bundle;import android.text.Editable;import android.text.TextWatcher;import android.view.View;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends Activity {private EditText editText;private TextView tip;private final int charMaxNum = 10; // 允許輸入的字數@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);init();}private void init() {editText = (EditText) findViewById(R.id.main_et);editText.addTextChangedListener(new EditChangedListener());tip = (TextView) findViewById(R.id.main_tv);tip.setText("0/"+charMaxNum);}class EditChangedListener implements TextWatcher {private CharSequence temp; // 監聽前的文本private int editStart; // 游標開始位置private int editEnd; // 游標結束位置// 輸入文本之前的狀態@Overridepublic void beforeTextChanged(CharSequence s, int start, int count,int after) {temp = s;}// 輸入文字中的狀態，count是一次性輸入字元數@Overridepublic void onTextChanged(CharSequence s, int start, int before, int count) {//if (charMaxNum - s.length() <= 5) {//tip.setText("還能輸入" + (charMaxNum - s.length()) + "字元");//}tip.setText((s.length()) + "/" + charMaxNum);}// 輸入文字後的狀態@Overridepublic void afterTextChanged(Editable s) {/** 得到游標開始和結束位置 ,超過最大數後記錄剛超出的數字索引進行控制 */editStart = editText.getSelectionStart();editEnd = editText.getSelectionEnd();if (temp.length() > charMaxNum) {//Toast.makeText(getApplicationContext(), "最多輸入10個字元", Toast.LENGTH_SHORT).show();s.delete(editStart - 1, editEnd);editText.setText(s);editText.setSelection(s.length());}}};}

二、資料類型檢驗，當輸入不是整型數位時候，會立刻彈出輸入框，提示改正
MainActivity：

package chay.mian;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.os.Bundle;import android.text.Editable;import android.text.TextWatcher;import android.util.Log;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends Activity {private EditText editText;private TextView tip;String str;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_mian);init();}private void init() {editText = (EditText) findViewById(R.id.mian_et);editText.addTextChangedListener(new EditChangedListener());tip = (TextView) findViewById(R.id.mian_tv);tip.setText("請輸入整型數字");}class EditChangedListener implements TextWatcher {// 輸入文本之前的狀態@Overridepublic void beforeTextChanged(CharSequence s, int start, int count, int after) {Log.d("TAG", "beforeTextChanged--------------->");}// 輸入文字中的狀態，count是一次性輸入字元數@Overridepublic void onTextChanged(CharSequence s, int start, int before, int count) {Log.d("TAG", "onTextChanged--------------->");}// 輸入文字後的狀態@Overridepublic void afterTextChanged(Editable s) {Log.d("TAG", "afterTextChanged--------------->");str = editText.getText().toString();try {//if ((editText.getText().toString()) != null)Integer.parseInt(str);} catch (Exception e) {showDialog();}}};private void showDialog() {AlertDialog dialog;AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("訊息").setIcon(android.R.drawable.stat_notify_error);builder.setMessage("你輸出的整型數字有誤，請改正");builder.setPositiveButton("確定", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stub}});dialog = builder.create();dialog.show();}}

在LogCat查看調用這些方法的順序：
beforeTextChanged-->onTextChanged-->onTextChanged

歡迎交流 http://blog.csdn.net/ycwol/article/details/46594275

android 監聽EditText 的變化