Java tutorial
/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.text.method; import android.annotation.UnsupportedAppUsage; import android.graphics.Rect; import android.os.Build; import android.os.Handler; import android.os.SystemClock; import android.text.Editable; import android.text.GetChars; import android.text.NoCopySpan; import android.text.Spannable; import android.text.Spanned; import android.text.TextUtils; import android.text.TextWatcher; import android.text.style.UpdateLayout; import android.view.View; import java.lang.ref.WeakReference; public class PasswordTransformationMethod implements TransformationMethod, TextWatcher { 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 PasswordTransformationMethod getInstance() { if (sInstance != null) return sInstance; sInstance = new PasswordTransformationMethod(); return sInstance; } public void beforeTextChanged(CharSequence s, int start, int count, int after) { // This callback isn't used. } public void onTextChanged(CharSequence s, int start, int before, int count) { if (s instanceof Spannable) { Spannable sp = (Spannable) s; ViewReference[] vr = sp.getSpans(0, s.length(), ViewReference.class); if (vr.length == 0) { return; } /* * There should generally only be one ViewReference in the text, * but make sure to look through all of them if necessary in case * something strange is going on. (We might still end up with * multiple ViewReferences if someone moves text from one password * field to another.) */ View v = null; for (int i = 0; v == null && i < vr.length; i++) { v = vr[i].get(); } if (v == null) { return; } int pref = TextKeyListener.getInstance().getPrefs(v.getContext()); if ((pref & TextKeyListener.SHOW_PASSWORD) != 0) { if (count > 0) { removeVisibleSpans(sp); if (count == 1) { sp.setSpan(new Visible(sp, this), start, start + count, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); } } } } } public void afterTextChanged(Editable s) { // This callback isn't used. } public void onFocusChanged(View view, CharSequence sourceText, boolean focused, int direction, Rect previouslyFocusedRect) { if (!focused) { if (sourceText instanceof Spannable) { Spannable sp = (Spannable) sourceText; removeVisibleSpans(sp); } } } private static void removeVisibleSpans(Spannable sp) { Visible[] old = sp.getSpans(0, sp.length(), Visible.class); for (int i = 0; i < old.length; i++) { sp.removeSpan(old[i]); } } private static class PasswordCharSequence implements CharSequence, GetChars { public PasswordCharSequence(CharSequence source) { mSource = source; } public int length() { return mSource.length(); } public char charAt(int i) { if (mSource instanceof Spanned) { Spanned sp = (Spanned) mSource; int st = sp.getSpanStart(TextKeyListener.ACTIVE); int en = sp.getSpanEnd(TextKeyListener.ACTIVE); if (i >= st && i < en) { return mSource.charAt(i); } Visible[] visible = sp.getSpans(0, sp.length(), Visible.class); for (int a = 0; a < visible.length; a++) { if (sp.getSpanStart(visible[a].mTransformer) >= 0) { st = sp.getSpanStart(visible[a]); en = sp.getSpanEnd(visible[a]); if (i >= st && i < en) { return mSource.charAt(i); } } } } return DOT; } public CharSequence subSequence(int start, int end) { char[] buf = new char[end - start]; getChars(start, end, buf, 0); return new String(buf); } public String toString() { return subSequence(0, length()).toString(); } public void getChars(int start, int end, char[] dest, int off) { TextUtils.getChars(mSource, start, end, dest, off); int st = -1, en = -1; int nvisible = 0; int[] starts = null, ends = null; if (mSource instanceof Spanned) { Spanned sp = (Spanned) mSource; st = sp.getSpanStart(TextKeyListener.ACTIVE); en = sp.getSpanEnd(TextKeyListener.ACTIVE); Visible[] visible = sp.getSpans(0, sp.length(), Visible.class); nvisible = visible.length; starts = new int[nvisible]; ends = new int[nvisible]; for (int i = 0; i < nvisible; i++) { if (sp.getSpanStart(visible[i].mTransformer) >= 0) { starts[i] = sp.getSpanStart(visible[i]); ends[i] = sp.getSpanEnd(visible[i]); } } } for (int i = start; i < end; i++) { if (!(i >= st && i < en)) { boolean visible = false; for (int a = 0; a < nvisible; a++) { if (i >= starts[a] && i < ends[a]) { visible = true; break; } } if (!visible) { dest[i - start + off] = DOT; } } } } private CharSequence mSource; } private static class Visible extends Handler implements UpdateLayout, Runnable { public Visible(Spannable sp, PasswordTransformationMethod ptm) { mText = sp; mTransformer = ptm; postAtTime(this, SystemClock.uptimeMillis() + 1500); } public void run() { mText.removeSpan(this); } private Spannable mText; private PasswordTransformationMethod mTransformer; } /** * Used to stash a reference back to the View in the Editable so we * can use it to check the settings. */ private static class ViewReference extends WeakReference<View> implements NoCopySpan { public ViewReference(View v) { super(v); } } @UnsupportedAppUsage private static PasswordTransformationMethod sInstance; @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) private static char DOT = '\u2022'; }