Will的部落格

若想處理editText元件中文字變動的事件，

就可實作textWathcer介面，

並用editText元件呼叫addTextChangedListener()註冊textWatcher的監聽，

 此範例為監聽editText的更動，並將輸入的密碼顯示於textView上。

MainActivity.java

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 passwordEditText;
    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        /* Initializing views */
        passwordEditText = (EditText) findViewById(R.id.password);
        textView = (TextView) findViewById(R.id.passwordHint);
        textView.setVisibility(View.GONE);

        /* Set Text Watcher listener */
        passwordEditText.addTextChangedListener(passwordWatcher);
    }

    private final TextWatcher passwordWatcher = new TextWatcher() {
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        public void onTextChanged(CharSequence s, int start, int before, int count) {
            textView.setVisibility(View.VISIBLE);
        }

        public void afterTextChanged(Editable s) {
            if (s.length() == 0) {
                textView.setVisibility(View.GONE);
            } else{
                textView.setText("You have entered : " + passwordEditText.getText());
            }
        }
    };
}

 activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:padding="10dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingBottom="10dp"
        android:text="Enter your password"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:textStyle="bold" />

    <EditText
        android:id="@+id/password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Password"
        android:inputType="textPassword"
        android:padding="12dp">

        <requestFocus />
    </EditText>

    <TextView
        android:id="@+id/passwordHint"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/password"
        android:background="#ffd33a26"
        android:padding="5dp"
        android:text="* Not Entered"
        android:textColor="#fff" />
</LinearLayout>

 
ps. 也可改用以下方式註冊監聽事件

passwordEditText.addTextChangedListener(new TextWatcher() {
            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

                // TODO Auto-generated method stub
            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                // TODO Auto-generated method stub
            }

            @Override
            public void afterTextChanged(Editable s) {
      
                // TODO Auto-generated method stud
            }
        });