PasswordTransformationMethod

/*
 * 修改PasswordTransformationMethod源码
 * 
 */

import android.os.Handler;
import android.os.SystemClock;
import android.graphics.Rect;
import android.view.View;
import android.text.Editable;
import android.text.GetChars;
import android.text.NoCopySpan;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.text.Spanned;
import android.text.Spannable;
import android.text.method.TransformationMethod;
import android.text.style.UpdateLayout;

import java.lang.ref.WeakReference;

public class MPasswordTransformationMethod
implements TransformationMethod, TextWatcher
{
//笨方法，从别的包引用的静态常量直接在类里定义
private static final Object TextKeyListener_ACTIVE = new NoCopySpan.Concrete(); 

    public CharSequence getTransformation(CharSequence source, View view) {
        if (source instanceof Spannable) {
            Spannable sp = (Spannable) source;

            /**
             * Remove any references to other views that may still be
             * attached.  This will happen when you flip the screen
             * while a password field is showing; there will still
             * be references to the old EditText in the text.
             */
            ViewReference[] vr = sp.getSpans(0, sp.length(),
                                             ViewReference.class);
            for (int i = 0; i < vr.length; i++) {
                sp.removeSpan(vr[i]);
            }

            removeVisibleSpans(sp);

            sp.setSpan(new ViewReference(view), 0, 0,
                       Spannable.SPAN_POINT_POINT);
        }

        return new PasswordCharSequence(source);
    }

    public static MPasswordTransformationMethod getInstance() {
        if (sInstance != null)
            return sInstance;

        sInstance = new MPasswordTransformationMethod();
        return sInstance;
    }