android 监听EditText 的变化
使用EditText的addTextChangedListener(TextWatcher watcher)方法对EditText实现监听,TextWatcher是一个接口类,所以必须实现TextWatcher里的抽象方法:
当EditText里面的内容有变化的时候,触发TextChangedListener事件,就会调用TextWatcher里面的抽象方法。
布局:
一、实现监听文本框字数,提示还能输入多少个字符
MainActivity:
欢迎交流 http://blog.csdn.net/ycwol/article/details/46594275
当EditText里面的内容有变化的时候,触发TextChangedListener事件,就会调用TextWatcher里面的抽象方法。
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>
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; // 允许输入的字数
- @Override
- protected 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; // 监听前的文本
- private int editStart; // 光标开始位置
- private int editEnd; // 光标结束位置
- // 输入文本之前的状态
- @Override
- public void beforeTextChanged(CharSequence s, int start, int count,int after) {
- temp = s;
- }
- // 输入文字中的状态,count是一次性输入字符数
- @Override
- public void onTextChanged(CharSequence s, int start, int before, int count) {
- // if (charMaxNum - s.length() <= 5) {
- // tip.setText("还能输入" + (charMaxNum - s.length()) + "字符");
- // }
- tip.setText((s.length()) + "/" + charMaxNum);
- }
- // 输入文字后的状态
- @Override
- public void afterTextChanged(Editable s) {
- /** 得到光标开始和结束位置 ,超过最大数后记录刚超出的数字索引进行控制 */
- editStart = editText.getSelectionStart();
- editEnd = editText.getSelectionEnd();
- if (temp.length() > charMaxNum) {
- // Toast.makeText(getApplicationContext(), "最多输入10个字符", Toast.LENGTH_SHORT).show();
- s.delete(editStart - 1, editEnd);
- editText.setText(s);
- editText.setSelection(s.length());
- }
- }
- };
- }
二、数据类型检验,当输入不是整型数字的时候,会立刻弹出输入框,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;
- @Override
- protected 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("请输入整型数字");
- }
- class EditChangedListener implements TextWatcher {
- // 输入文本之前的状态
- @Override
- public void beforeTextChanged(CharSequence s, int start, int count, int after) {
- Log.d("TAG", "beforeTextChanged--------------->");
- }
- // 输入文字中的状态,count是一次性输入字符数
- @Override
- public void onTextChanged(CharSequence s, int start, int before, int count) {
- Log.d("TAG", "onTextChanged--------------->");
- }
- // 输入文字后的状态
- @Override
- public 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("消息").setIcon(android.R.drawable.stat_notify_error);
- builder.setMessage("你输出的整型数字有误,请改正");
- builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
- @Override
- public void onClick(DialogInterface dialog, int which) {
- // TODO Auto-generated method stub
- }
- });
- dialog = builder.create();
- dialog.show();
- }
- }
欢迎交流 http://blog.csdn.net/ycwol/article/details/46594275