Refactor autocomplete-specific logic into a separate class

chrome/android/java/src/org/chromium/chrome/browser/omnibox/view/AutocompleteEditText.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.omnibox.view;

[Ted C, 2017/05/17 18:29:33]

I wouldn't introduce a new package yet.  The omnibox package is primarily view
stuff right now.

[Changwan Ryu, 2017/05/17 20:18:57]

Done.

+
+import android.content.Context;
+import android.graphics.Rect;
+import android.os.StrictMode;
+import android.text.Editable;
+import android.text.Selection;
+import android.text.Spanned;
+import android.text.TextUtils;
+import android.util.AttributeSet;
+import android.view.accessibility.AccessibilityEvent;
+import android.view.accessibility.AccessibilityManager;
+import android.view.accessibility.AccessibilityNodeInfo;
+import android.view.inputmethod.BaseInputConnection;
+import android.view.inputmethod.EditorInfo;
+import android.view.inputmethod.InputConnection;
+import android.view.inputmethod.InputConnectionWrapper;
+import android.widget.EditText;
+
+import org.chromium.base.Log;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.chrome.browser.widget.VerticallyFixedEditText;
+
+/**
+ * An {@link EditText} that shows autocomplete text at the end.
+ */
+public class AutocompleteEditText extends VerticallyFixedEditText {
+    private static final String TAG = "cr_AutocompleteEdit";
+
+    private static final boolean DEBUG = false;

[Ted C, 2017/05/17 18:29:33]

should we make this protected and have UrlBar key off the same value?

[Changwan Ryu, 2017/05/17 20:18:57]

At least for me, I prefer to keep DEBUG value separately for each file. Then I
can
keep a combination of them as a commit and rebase it as necessary. I looked up
and most of the files (although not many) have separate DEBUG values.

+
+    private final AutocompleteSpan mAutocompleteSpan;
+    private final AccessibilityManager mAccessibilityManager;
+
+    /**
+     * Whether default TextView scrolling should be disabled because autocomplete has been added.
+     * This allows the user entered text to be shown instead of the end of the autocomplete.
+     */
+    private boolean mDisableTextScrollingFromAutocomplete;
+
+    private boolean mInBatchEditMode;
+    private int mBeforeBatchEditAutocompleteIndex = -1;
+    private String mBeforeBatchEditFullText;
+    private boolean mSelectionChangedInBatchMode;
+    private boolean mTextDeletedInBatchMode;
+
+    private boolean mIsPastedText;
+
+    // Set to true when the text is modified programmatically. Initially set to true until the old
+    // state has been loaded.
+    private boolean mIgnoreTextChangeFromAutocomplete = true;
+    private boolean mLastEditWasDelete;
+
+    public AutocompleteEditText(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        mAutocompleteSpan = new AutocompleteSpan();
+        mAccessibilityManager =
+                (AccessibilityManager) context.getSystemService(Context.ACCESSIBILITY_SERVICE);
+    }
+
+    /**
+     * Sets whether text changes should trigger autocomplete.
+     *
+     * @param ignoreAutocomplete Whether text changes should be ignored and no auto complete
+     *                           triggered.
+     */
+    public void setIgnoreTextChangesForAutocomplete(boolean ignoreAutocomplete) {
+        if (DEBUG) Log.i(TAG, "setIgnoreTextChangesForAutocomplete: " + ignoreAutocomplete);
+        mIgnoreTextChangeFromAutocomplete = ignoreAutocomplete;
+    }
+
+    /** @return Text that includes autocomplete. */
+    public String getTextWithAutocomplete() {
+        return getEditableText() != null ? getEditableText().toString() : "";
+    }
+
+    /**
+     * @return Whether the current cursor position is at the end of the user typed text (i.e.
+     *         at the beginning of the inline autocomplete text if present otherwise the very
+     *         end of the current text).
+     */
+    private boolean isCursorAtEndOfTypedText() {
+        final int selectionStart = getSelectionStart();
+        final int selectionEnd = getSelectionEnd();
+
+        int expectedSelectionStart = getText().getSpanStart(mAutocompleteSpan);
+        int expectedSelectionEnd = getText().length();
+        if (expectedSelectionStart < 0) {
+            expectedSelectionStart = expectedSelectionEnd;
+        }
+
+        return selectionStart == expectedSelectionStart && selectionEnd == expectedSelectionEnd;
+    }
+
+    /**
+     * @return Whether the URL is currently in batch edit mode triggered by an IME.  No external
+     *         text changes should be triggered while this is true.
+     */
+    // isInBatchEditMode is a package protected method on TextView, so we intentionally chose
+    // a different name.
+    private boolean isHandlingBatchInput() {
+        return mInBatchEditMode;
+    }
+
+    /**
+     * @return The user text without the autocomplete text.
+     */
+    public String getTextWithoutAutocomplete() {
+        int autoCompleteIndex = getText().getSpanStart(mAutocompleteSpan);
+        if (autoCompleteIndex < 0) {
+            return getTextWithAutocomplete();
+        } else {
+            return getTextWithAutocomplete().substring(0, autoCompleteIndex);
+        }
+    }
+
+    /** @return Whether any autocomplete information is specified on the current text. */
+    @VisibleForTesting
+    public boolean hasAutocomplete() {
+        return getText().getSpanStart(mAutocompleteSpan) >= 0
+                || mAutocompleteSpan.mAutocompleteText != null
+                || mAutocompleteSpan.mUserText != null;
+    }
+
+    /**
+     * Whether we want to be showing inline autocomplete results. We don't want to show them as the
+     * user deletes input. Also if there is a composition (e.g. while using the Japanese IME),
+     * we must not autocomplete or we'll destroy the composition.
+     * @return Whether we want to be showing inline autocomplete results.
+     */
+    public boolean shouldAutocomplete() {
+        if (mLastEditWasDelete) return false;
+        Editable text = getText();
+
+        return isCursorAtEndOfTypedText() && !isPastedText() && !isHandlingBatchInput()
+                && BaseInputConnection.getComposingSpanEnd(text)
+                == BaseInputConnection.getComposingSpanStart(text);
+    }
+
+    @Override
+    public void onBeginBatchEdit() {
+        if (DEBUG) Log.i(TAG, "onBeginBatchEdit");
+        mBeforeBatchEditAutocompleteIndex = getText().getSpanStart(mAutocompleteSpan);
+        mBeforeBatchEditFullText = getText().toString();
+
+        super.onBeginBatchEdit();
+        mInBatchEditMode = true;
+        mTextDeletedInBatchMode = false;
+    }
+
+    @Override
+    public void onEndBatchEdit() {
+        if (DEBUG) Log.i(TAG, "onEndBatchEdit");
+        super.onEndBatchEdit();
+        mInBatchEditMode = false;
+        if (mSelectionChangedInBatchMode) {
+            validateSelection(getSelectionStart(), getSelectionEnd());
+            mSelectionChangedInBatchMode = false;
+        }
+
+        String newText = getText().toString();
+        if (!TextUtils.equals(mBeforeBatchEditFullText, newText)
+                || getText().getSpanStart(mAutocompleteSpan) != mBeforeBatchEditAutocompleteIndex) {
+            // If the text being typed is a single character that matches the next character in the
+            // previously visible autocomplete text, we reapply the autocomplete text to prevent
+            // a visual flickering when the autocomplete text is cleared and then quickly reapplied
+            // when the next round of suggestions is received.
+            if (shouldAutocomplete() && mBeforeBatchEditAutocompleteIndex != -1
+                    && mBeforeBatchEditFullText != null
+                    && mBeforeBatchEditFullText.startsWith(newText) && !mTextDeletedInBatchMode
+                    && newText.length() - mBeforeBatchEditAutocompleteIndex == 1) {
+                setAutocompleteText(newText, mBeforeBatchEditFullText.substring(newText.length()));
+            }
+            notifyAutocompleteTextStateChanged(mTextDeletedInBatchMode, true);
+        }
+
+        mTextDeletedInBatchMode = false;
+        mBeforeBatchEditAutocompleteIndex = -1;
+        mBeforeBatchEditFullText = null;
+    }
+
+    @Override
+    protected void onSelectionChanged(int selStart, int selEnd) {
+        if (DEBUG) Log.i(TAG, "onSelectionChanged -- selStart: %d, selEnd: %d", selStart, selEnd);
+        if (!mInBatchEditMode) {
+            int beforeTextLength = getText().length();
+            if (validateSelection(selStart, selEnd)) {
+                boolean textDeleted = getText().length() < beforeTextLength;
+                notifyAutocompleteTextStateChanged(textDeleted, false);
+            }
+        } else {
+            mSelectionChangedInBatchMode = true;
+        }
+        super.onSelectionChanged(selStart, selEnd);
+    }
+
+    /**
+     * Validates the selection and clears the autocomplete span if needed.  The autocomplete text
+     * will be deleted if the selection occurs entirely before the autocomplete region.
+     *
+     * @param selStart The start of the selection.
+     * @param selEnd The end of the selection.
+     * @return Whether the autocomplete span was removed as a result of this validation.
+     */
+    private boolean validateSelection(int selStart, int selEnd) {
+        int spanStart = getText().getSpanStart(mAutocompleteSpan);
+        int spanEnd = getText().getSpanEnd(mAutocompleteSpan);
+
+        if (DEBUG) {
+            Log.i(TAG, "validateSelection -- selStart: %d, selEnd: %d, spanStart: %d, spanEnd: %d",
+                    selStart, selEnd, spanStart, spanEnd);
+        }
+
+        if (spanStart >= 0 && (spanStart != selStart || spanEnd != selEnd)) {
+            CharSequence previousAutocompleteText = mAutocompleteSpan.mAutocompleteText;
+
+            // On selection changes, the autocomplete text has been accepted by the user or needs
+            // to be deleted below.
+            mAutocompleteSpan.clearSpan();
+
+            // The autocomplete text will be deleted any time the selection occurs entirely before
+            // the start of the autocomplete text.  This is required because certain keyboards will
+            // insert characters temporarily when starting a key entry gesture (whether it be
+            // swyping a word or long pressing to get a special character).  When this temporary
+            // character appears, Chrome may decide to append some autocomplete, but the keyboard
+            // will then remove this temporary character only while leaving the autocomplete text
+            // alone.  See crbug/273763 for more details.
+            if (selEnd <= spanStart
+                    && TextUtils.equals(previousAutocompleteText,
+                               getText().subSequence(spanStart, getText().length()))) {
+                getText().delete(spanStart, getText().length());
+            }
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
+        if (!focused) mAutocompleteSpan.clearSpan();
+        super.onFocusChanged(focused, direction, previouslyFocusedRect);
+    }
+
+    @Override
+    public boolean bringPointIntoView(int offset) {
+        if (mDisableTextScrollingFromAutocomplete) return false;
+        return super.bringPointIntoView(offset);
+    }
+
+    @Override
+    public boolean onPreDraw() {
+        boolean retVal = super.onPreDraw();
+        if (mDisableTextScrollingFromAutocomplete) {
+            // super.onPreDraw will put the selection at the end of the text selection, but
+            // in the case of autocomplete we want the last typed character to be shown, which
+            // is the start of selection.
+            mDisableTextScrollingFromAutocomplete = false;
+            bringPointIntoView(getSelectionStart());
+            retVal = true;
+        }
+        return retVal;
+    }
+
+    /** Call this when text is pasted. */
+    public void onPaste() {
+        mIsPastedText = true;
+    }
+
+    /**
+     * Autocompletes the text on the url bar and selects the text that was not entered by the
+     * user. Using append() instead of setText() to preserve the soft-keyboard layout.
+     * @param userText user The text entered by the user.
+     * @param inlineAutocompleteText The suggested autocompletion for the user's text.
+     */
+    public void setAutocompleteText(CharSequence userText, CharSequence inlineAutocompleteText) {
+        if (DEBUG) {
+            Log.i(TAG, "setAutocompleteText -- userText: %s, inlineAutocompleteText: %s", userText,
+                    inlineAutocompleteText);
+        }
+        boolean emptyAutocomplete = TextUtils.isEmpty(inlineAutocompleteText);
+
+        if (!emptyAutocomplete) mDisableTextScrollingFromAutocomplete = true;
+
+        int autocompleteIndex = userText.length();
+
+        String previousText = getTextWithAutocomplete();
+        CharSequence newText = TextUtils.concat(userText, inlineAutocompleteText);
+
+        setIgnoreTextChangesForAutocomplete(true);
+
+        if (!TextUtils.equals(previousText, newText)) {
+            // The previous text may also have included autocomplete text, so we only
+            // append the new autocomplete text that has changed.
+            if (TextUtils.indexOf(newText, previousText) == 0) {
+                append(newText.subSequence(previousText.length(), newText.length()));
+            } else {
+                setTextFromAutocomplete(newText.toString());
+            }
+        }
+
+        if (getSelectionStart() != autocompleteIndex || getSelectionEnd() != getText().length()) {
+            setSelection(autocompleteIndex, getText().length());
+
+            if (inlineAutocompleteText.length() != 0) {
+                // Sending a TYPE_VIEW_TEXT_SELECTION_CHANGED accessibility event causes the
+                // previous TYPE_VIEW_TEXT_CHANGED event to be swallowed. As a result the user
+                // hears the autocomplete text but *not* the text they typed. Instead we send a
+                // TYPE_ANNOUNCEMENT event, which doesn't swallow the text-changed event.
+                announceForAccessibility(inlineAutocompleteText);
+            }
+        }
+
+        if (emptyAutocomplete) {
+            mAutocompleteSpan.clearSpan();
+        } else {
+            mAutocompleteSpan.setSpan(userText, inlineAutocompleteText);
+        }
+
+        setIgnoreTextChangesForAutocomplete(false);
+    }
+
+    /**
+     * Returns the length of the autocomplete text currently displayed, zero if none is
+     * currently displayed.
+     */
+    public int getAutocompleteLength() {
+        int autoCompleteIndex = getText().getSpanStart(mAutocompleteSpan);
+        if (autoCompleteIndex < 0) return 0;
+        return getText().length() - autoCompleteIndex;
+    }
+
+    @Override
+    protected void onTextChanged(CharSequence text, int start, int lengthBefore, int lengthAfter) {
+        if (DEBUG) {
+            Log.i(TAG, "onTextChanged -- text: %s, start: %d, lengthBefore: %d, lengthAfter: %d",
+                    text, start, lengthBefore, lengthAfter);
+        }
+
+        super.onTextChanged(text, start, lengthBefore, lengthAfter);
+        boolean textDeleted = lengthAfter == 0;
+        if (!mInBatchEditMode) {
+            notifyAutocompleteTextStateChanged(textDeleted, true);
+        } else {
+            mTextDeletedInBatchMode = textDeleted;
+        }
+        mIsPastedText = false;
+    }
+
+    @Override
+    public void setText(CharSequence text, BufferType type) {
+        if (DEBUG) Log.i(TAG, "setText -- text: %s", text);
+
+        mDisableTextScrollingFromAutocomplete = false;
+
+        // Avoid setting the same text to the URL bar as it will mess up the scroll/cursor
+        // position.
+        // Setting the text is also quite expensive, so only do it when the text has changed
+        // (since we apply spans when the URL is not focused, we only optimize this when the
+        // URL is being edited).
+        if (!TextUtils.equals(getEditableText(), text)) {
+            // Certain OEM implementations of setText trigger disk reads. crbug.com/633298
+            StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
+            try {
+                super.setText(text, type);
+            } finally {
+                StrictMode.setThreadPolicy(oldPolicy);
+            }
+        }
+
+        // Verify the autocomplete is still valid after the text change.
+        // Note: mAutocompleteSpan may be still null here if setText() is called in View
+        // constructor.
+        if (mAutocompleteSpan != null && mAutocompleteSpan.mUserText != null
+                && mAutocompleteSpan.mAutocompleteText != null) {
+            if (getText().getSpanStart(mAutocompleteSpan) < 0) {
+                mAutocompleteSpan.clearSpan();
+            } else {
+                clearAutocompleteSpanIfInvalid();
+            }
+        }
+    }
+
+    private void clearAutocompleteSpanIfInvalid() {
+        Editable editableText = getEditableText();
+        CharSequence previousUserText = mAutocompleteSpan.mUserText;
+        CharSequence previousAutocompleteText = mAutocompleteSpan.mAutocompleteText;
+        if (editableText.length()
+                != (previousUserText.length() + previousAutocompleteText.length())) {
+            mAutocompleteSpan.clearSpan();
+        } else if (TextUtils.indexOf(getText(), previousUserText) != 0
+                || TextUtils.indexOf(getText(), previousAutocompleteText, previousUserText.length())
+                        != 0) {
+            mAutocompleteSpan.clearSpan();
+        }
+    }
+
+    @Override
+    public void sendAccessibilityEventUnchecked(AccessibilityEvent event) {
+        if (mIgnoreTextChangeFromAutocomplete) {
+            if (event.getEventType() == AccessibilityEvent.TYPE_VIEW_TEXT_SELECTION_CHANGED
+                    || event.getEventType() == AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED) {
+                return;
+            }
+        }
+        super.sendAccessibilityEventUnchecked(event);
+    }
+
+    @Override
+    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
+        // Certain OEM implementations of onInitializeAccessibilityNodeInfo trigger disk reads
+        // to access the clipboard.  crbug.com/640993
+        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
+        try {
+            super.onInitializeAccessibilityNodeInfo(info);
+        } finally {
+            StrictMode.setThreadPolicy(oldPolicy);
+        }
+    }
+
+    @VisibleForTesting
+    public InputConnectionWrapper getInputConnection() {
+        return mInputConnection;
+    }
+
+    private InputConnectionWrapper mInputConnection = new InputConnectionWrapper(null, true) {
+        private final char[] mTempSelectionChar = new char[1];
+
+        @Override
+        public boolean commitText(CharSequence text, int newCursorPosition) {
+            if (DEBUG) Log.i(TAG, "commitText: [%s]", text);
+            Editable currentText = getText();
+            if (currentText == null) return super.commitText(text, newCursorPosition);
+
+            int selectionStart = Selection.getSelectionStart(currentText);
+            int selectionEnd = Selection.getSelectionEnd(currentText);
+            int autocompleteIndex = currentText.getSpanStart(mAutocompleteSpan);
+            // If the text being committed is a single character that matches the next character
+            // in the selection (assumed to be the autocomplete text), we only move the text
+            // selection instead clearing the autocomplete text causing flickering as the
+            // autocomplete text will appear once the next suggestions are received.
+            //
+            // To be confident that the selection is an autocomplete, we ensure the selection
+            // is at least one character and the end of the selection is the end of the
+            // currently entered text.
+            if (newCursorPosition == 1 && selectionStart > 0 && selectionStart != selectionEnd
+                    && selectionEnd >= currentText.length() && autocompleteIndex == selectionStart
+                    && text.length() == 1) {
+                currentText.getChars(selectionStart, selectionStart + 1, mTempSelectionChar, 0);
+                if (mTempSelectionChar[0] == text.charAt(0)) {
+                    // Since the text isn't changing, TalkBack won't read out the typed characters.
+                    // To work around this, explicitly send an accessibility event. crbug.com/416595
+                    if (mAccessibilityManager != null && mAccessibilityManager.isEnabled()) {
+                        AccessibilityEvent event = AccessibilityEvent.obtain(
+                                AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED);
+                        event.setFromIndex(selectionStart);
+                        event.setRemovedCount(0);
+                        event.setAddedCount(1);
+                        event.setBeforeText(currentText.toString().substring(0, selectionStart));
+                        sendAccessibilityEventUnchecked(event);
+                    }
+
+                    setAutocompleteText(currentText.subSequence(0, selectionStart + 1),
+                            currentText.subSequence(selectionStart + 1, selectionEnd));
+                    if (!mInBatchEditMode) {
+                        notifyAutocompleteTextStateChanged(false, false);
+                    }
+                    return true;
+                }
+            }
+
+            boolean retVal = super.commitText(text, newCursorPosition);
+
+            // Ensure the autocomplete span is removed if it is no longer valid after committing the
+            // text.
+            if (getText().getSpanStart(mAutocompleteSpan) >= 0) clearAutocompleteSpanIfInvalid();
+
+            return retVal;
+        }
+
+        @Override
+        public boolean setComposingText(CharSequence text, int newCursorPosition) {
+            if (DEBUG) Log.i(TAG, "setComposingText: [%s]", text);
+            Editable currentText = getText();
+            int autoCompleteSpanStart = currentText.getSpanStart(mAutocompleteSpan);
+            if (autoCompleteSpanStart >= 0) {
+                int composingEnd = BaseInputConnection.getComposingSpanEnd(currentText);
+
+                // On certain device/keyboard combinations, the composing regions are specified
+                // with a noticeable delay after the initial character is typed, and in certain
+                // circumstances it does not check that the current state of the text matches the
+                // expectations of it's composing region.
+                // For example, you can be typing:
+                //   chrome://f
+                // Chrome will autocomplete to:
+                //   chrome://f[lags]
+                // And after the autocomplete has been set, the keyboard will set the composing
+                // region to the last character and it assumes it is 'f' as it was the last
+                // character the keyboard sent.  If we commit this composition, the text will
+                // look like:
+                //   chrome://flag[f]
+                // And if we use the autocomplete clearing logic below, it will look like:
+                //   chrome://f[f]
+                // To work around this, we see if the composition matches all the characters prior
+                // to the autocomplete and just readjust the composing region to be that subset.
+                //
+                // See crbug.com/366732
+                if (composingEnd == currentText.length() && autoCompleteSpanStart >= text.length()
+                        && TextUtils.equals(
+                                   currentText.subSequence(autoCompleteSpanStart - text.length(),
+                                           autoCompleteSpanStart),
+                                   text)) {
+                    setComposingRegion(
+                            autoCompleteSpanStart - text.length(), autoCompleteSpanStart);
+                }
+
+                // Once composing text is being modified, the autocomplete text has been accepted
+                // or has to be deleted.
+                mAutocompleteSpan.clearSpan();
+                Selection.setSelection(currentText, autoCompleteSpanStart);
+                currentText.delete(autoCompleteSpanStart, currentText.length());
+            }
+            return super.setComposingText(text, newCursorPosition);
+        }
+    };
+
+    @Override
+    public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
+        if (DEBUG) Log.i(TAG, "onCreateInputConnection");
+        return createInputConnection(super.onCreateInputConnection(outAttrs));
+    }
+
+    @VisibleForTesting
+    public InputConnection createInputConnection(InputConnection target) {
+        mInputConnection.setTarget(target);
+        return mInputConnection;
+    }
+
+    /**
+     * @return Whether the current UrlBar input has been pasted from the clipboard.
+     */
+    public boolean isPastedText() {
+        return mIsPastedText;

[Ted C, 2017/05/17 18:29:33]

Does this need to be in this class?  Looks like it could be isolated entirely
within UrlBar?

[Changwan Ryu, 2017/05/17 20:18:57]

Done. Note that I overrode shouldAutocomplete() to check isPastedText() there.

+    }
+
+    private void notifyAutocompleteTextStateChanged(boolean textDeleted, boolean updateDisplay) {
+        if (DEBUG) {
+            Log.i(TAG, "notifyAutocompleteTextStateChanged: DEL[%b] DIS[%b] IGN[%b]", textDeleted,
+                    updateDisplay, mIgnoreTextChangeFromAutocomplete);
+        }
+        if (mIgnoreTextChangeFromAutocomplete) return;
+        if (!hasFocus()) return;
+        mLastEditWasDelete = textDeleted;
+        onAutocompleteTextStateChanged(textDeleted, updateDisplay);
+    }
+
+    /**
+     * This is called when autocomplete replaces the whole text.
+     *
+     * @param text The text.
+     */
+    public void setTextFromAutocomplete(String text) {

[Ted C, 2017/05/17 18:29:33]

seems like this should be protected.  We really don't want anyone to call this
from outside this or the child classes

maybe we should call this replaceAllTextFromAutocomplete?

[Changwan Ryu, 2017/05/17 20:18:57]

Done, thanks for the naming suggestion!

+        setText(text);
+    }
+
+    /**
+     * This is called when autocomplete text state changes.
+     * @param textDeleted True if text is just deleted.
+     * @param updateDisplay True if string is changed.
+     */
+    public void onAutocompleteTextStateChanged(boolean textDeleted, boolean updateDisplay) {}
+
+    /**
+     * Simple span used for tracking the current autocomplete state.
+     */
+    private class AutocompleteSpan {
+        private CharSequence mUserText;
+        private CharSequence mAutocompleteText;
+
+        /**
+         * Adds the span to the current text.
+         * @param userText The user entered text.
+         * @param autocompleteText The autocomplete text being appended.
+         */
+        public void setSpan(CharSequence userText, CharSequence autocompleteText) {
+            Editable text = getText();
+            text.removeSpan(this);
+            mAutocompleteText = autocompleteText;
+            mUserText = userText;
+            text.setSpan(this, userText.length(), text.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+        }
+
+        /** Removes this span from the current text and clears the internal state. */
+        public void clearSpan() {
+            getText().removeSpan(this);
+            mAutocompleteText = null;
+            mUserText = null;
+        }
+    }
+}