Android example source code file (DynamicLayout.java)

This example Android source code file (DynamicLayout.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, changewatcher, charsequence, dir_shift, directions, drawing, dynamiclayout, graphics, object, packedintvector, paint, spannable, spanned, start, staticlayout, style, tab_mask, text, textpaint, top

The DynamicLayout.java Android example source code

/*
 * 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;

import android.graphics.Paint;
import android.text.style.UpdateLayout;
import android.text.style.WrapTogetherSpan;

import java.lang.ref.WeakReference;

/**
 * DynamicLayout is a text layout that updates itself as the text is edited.
 * <p>This is used by widgets to control text layout. You should not need
 * to use this class directly unless you are implementing your own widget
 * or custom display object, or need to call
 * {@link android.graphics.Canvas#drawText(java.lang.CharSequence, int, int, float, float, android.graphics.Paint)
 *  Canvas.drawText()} directly.</p>
 */
public class DynamicLayout
extends Layout
{
    private static final int PRIORITY = 128;

    /**
     * Make a layout for the specified text that will be updated as
     * the text is changed.
     */
    public DynamicLayout(CharSequence base,
                         TextPaint paint,
                         int width, Alignment align,
                         float spacingmult, float spacingadd,
                         boolean includepad) {
        this(base, base, paint, width, align, spacingmult, spacingadd,
             includepad);
    }

    /**
     * Make a layout for the transformed text (password transformation
     * being the primary example of a transformation)
     * that will be updated as the base text is changed.
     */
    public DynamicLayout(CharSequence base, CharSequence display,
                         TextPaint paint,
                         int width, Alignment align,
                         float spacingmult, float spacingadd,
                         boolean includepad) {
        this(base, display, paint, width, align, spacingmult, spacingadd,
             includepad, null, 0);
    }

    /**
     * Make a layout for the transformed text (password transformation
     * being the primary example of a transformation)
     * that will be updated as the base text is changed.
     * If ellipsize is non-null, the Layout will ellipsize the text
     * down to ellipsizedWidth.
     */
    public DynamicLayout(CharSequence base, CharSequence display,
                         TextPaint paint,
                         int width, Alignment align,
                         float spacingmult, float spacingadd,
                         boolean includepad,
                         TextUtils.TruncateAt ellipsize, int ellipsizedWidth) {
        super((ellipsize == null) 
                ? display 
                : (display instanceof Spanned) 
                    ? new SpannedEllipsizer(display) 
                    : new Ellipsizer(display),
              paint, width, align, spacingmult, spacingadd);

        mBase = base;
        mDisplay = display;

        if (ellipsize != null) {
            mInts = new PackedIntVector(COLUMNS_ELLIPSIZE);
            mEllipsizedWidth = ellipsizedWidth;
            mEllipsizeAt = ellipsize;
        } else {
            mInts = new PackedIntVector(COLUMNS_NORMAL);
            mEllipsizedWidth = width;
            mEllipsizeAt = ellipsize;
        }

        mObjects = new PackedObjectVector<Directions>(1);

        mIncludePad = includepad;

        /*
         * This is annoying, but we can't refer to the layout until
         * superclass construction is finished, and the superclass
         * constructor wants the reference to the display text.
         *
         * This will break if the superclass constructor ever actually
         * cares about the content instead of just holding the reference.
         */
        if (ellipsize != null) {
            Ellipsizer e = (Ellipsizer) getText();

            e.mLayout = this;
            e.mWidth = ellipsizedWidth;
            e.mMethod = ellipsize;
            mEllipsize = true;
        }

        // Initial state is a single line with 0 characters (0 to 0),
        // with top at 0 and bottom at whatever is natural, and
        // undefined ellipsis.

        int[] start;

        if (ellipsize != null) {
            start = new int[COLUMNS_ELLIPSIZE];
            start[ELLIPSIS_START] = ELLIPSIS_UNDEFINED;
        } else {
            start = new int[COLUMNS_NORMAL];
        }

        Directions[] dirs = new Directions[] { DIRS_ALL_LEFT_TO_RIGHT };

        Paint.FontMetricsInt fm = paint.getFontMetricsInt();
        int asc = fm.ascent;
        int desc = fm.descent;

        start[DIR] = DIR_LEFT_TO_RIGHT << DIR_SHIFT;
        start[TOP] = 0;
        start[DESCENT] = desc;
        mInts.insertAt(0, start);

        start[TOP] = desc - asc;
        mInts.insertAt(1, start);

        mObjects.insertAt(0, dirs);

        // Update from 0 characters to whatever the real text is

        reflow(base, 0, 0, base.length());

        if (base instanceof Spannable) {
            if (mWatcher == null)
                mWatcher = new ChangeWatcher(this);

            // Strip out any watchers for other DynamicLayouts.
            Spannable sp = (Spannable) base;
            ChangeWatcher[] spans = sp.getSpans(0, sp.length(), ChangeWatcher.class);
            for (int i = 0; i < spans.length; i++)
                sp.removeSpan(spans[i]);

            sp.setSpan(mWatcher, 0, base.length(),
                       Spannable.SPAN_INCLUSIVE_INCLUSIVE |
                       (PRIORITY << Spannable.SPAN_PRIORITY_SHIFT));
        }
    }

    private void reflow(CharSequence s, int where, int before, int after) {
        if (s != mBase)
            return;

        CharSequence text = mDisplay;
        int len = text.length();

        // seek back to the start of the paragraph

        int find = TextUtils.lastIndexOf(text, '\n', where - 1);
        if (find < 0)
            find = 0;
        else
            find = find + 1;

        {
            int diff = where - find;
            before += diff;
            after += diff;
            where -= diff;
        }

        // seek forward to the end of the paragraph

        int look = TextUtils.indexOf(text, '\n', where + after);
        if (look < 0)
            look = len;
        else
            look++; // we want the index after the \n

        int change = look - (where + after);
        before += change;
        after += change;

        // seek further out to cover anything that is forced to wrap together

        if (text instanceof Spanned) {
            Spanned sp = (Spanned) text;
            boolean again;

            do {
                again = false;

                Object[] force = sp.getSpans(where, where + after,
                                             WrapTogetherSpan.class);

                for (int i = 0; i < force.length; i++) {
                    int st = sp.getSpanStart(force[i]);
                    int en = sp.getSpanEnd(force[i]);

                    if (st < where) {
                        again = true;

                        int diff = where - st;
                        before += diff;
                        after += diff;
                        where -= diff;
                    }

                    if (en > where + after) {
                        again = true;

                        int diff = en - (where + after);
                        before += diff;
                        after += diff;
                    }
                }
            } while (again);
        }

        // find affected region of old layout

        int startline = getLineForOffset(where);
        int startv = getLineTop(startline);

        int endline = getLineForOffset(where + before);
        if (where + after == len)
            endline = getLineCount();
        int endv = getLineTop(endline);
        boolean islast = (endline == getLineCount());

        // generate new layout for affected text

        StaticLayout reflowed;

        synchronized (sLock) {
            reflowed = sStaticLayout;
            sStaticLayout = null;
        }

        if (reflowed == null)
            reflowed = new StaticLayout(true);

        reflowed.generate(text, where, where + after,
                                      getPaint(), getWidth(), getAlignment(),
                                      getSpacingMultiplier(), getSpacingAdd(),
                                      false, true, mEllipsize,
                                      mEllipsizedWidth, mEllipsizeAt);
        int n = reflowed.getLineCount();

        // If the new layout has a blank line at the end, but it is not
        // the very end of the buffer, then we already have a line that
        // starts there, so disregard the blank line.

        if (where + after != len &&
            reflowed.getLineStart(n - 1) == where + after)
            n--;

        // remove affected lines from old layout

        mInts.deleteAt(startline, endline - startline);
        mObjects.deleteAt(startline, endline - startline);

        // adjust offsets in layout for new height and offsets

        int ht = reflowed.getLineTop(n);
        int toppad = 0, botpad = 0;

        if (mIncludePad && startline == 0) {
            toppad = reflowed.getTopPadding();
            mTopPadding = toppad;
            ht -= toppad;
        }
        if (mIncludePad && islast) {
            botpad = reflowed.getBottomPadding();
            mBottomPadding = botpad;
            ht += botpad;
        }

        mInts.adjustValuesBelow(startline, START, after - before);
        mInts.adjustValuesBelow(startline, TOP, startv - endv + ht);

        // insert new layout

        int[] ints;

        if (mEllipsize) {
            ints = new int[COLUMNS_ELLIPSIZE];
            ints[ELLIPSIS_START] = ELLIPSIS_UNDEFINED;
        } else {
            ints = new int[COLUMNS_NORMAL];
        }

        Directions[] objects = new Directions[1];


        for (int i = 0; i < n; i++) {
            ints[START] = reflowed.getLineStart(i) |
                          (reflowed.getParagraphDirection(i) << DIR_SHIFT) |
                          (reflowed.getLineContainsTab(i) ? TAB_MASK : 0);

            int top = reflowed.getLineTop(i) + startv;
            if (i > 0)
                top -= toppad;
            ints[TOP] = top;

            int desc = reflowed.getLineDescent(i);
            if (i == n - 1)
                desc += botpad;

            ints[DESCENT] = desc;
            objects[0] = reflowed.getLineDirections(i);

            if (mEllipsize) {
                ints[ELLIPSIS_START] = reflowed.getEllipsisStart(i);
                ints[ELLIPSIS_COUNT] = reflowed.getEllipsisCount(i);
            }

            mInts.insertAt(startline + i, ints);
            mObjects.insertAt(startline + i, objects);
        }

        synchronized (sLock) {
            sStaticLayout = reflowed;
        }
    }

    private void dump(boolean show) {
        int n = getLineCount();

        for (int i = 0; i < n; i++) {
            System.out.print("line " + i + ": " + getLineStart(i) + " to " + getLineEnd(i) + " ");

            if (show) {
                System.out.print(getText().subSequence(getLineStart(i),
                                                       getLineEnd(i)));
            }

            System.out.println("");
        }

        System.out.println("");
    }

    public int getLineCount() {
        return mInts.size() - 1;
    }

    public int getLineTop(int line) {
        return mInts.getValue(line, TOP);
    }

    public int getLineDescent(int line) {
        return mInts.getValue(line, DESCENT);
    }

    public int getLineStart(int line) {
        return mInts.getValue(line, START) & START_MASK;
    }

    public boolean getLineContainsTab(int line) {
        return (mInts.getValue(line, TAB) & TAB_MASK) != 0;
    }

    public int getParagraphDirection(int line) {
        return mInts.getValue(line, DIR) >> DIR_SHIFT;
    }

    public final Directions getLineDirections(int line) {
        return mObjects.getValue(line, 0);
    }

    public int getTopPadding() {
        return mTopPadding;
    }

    public int getBottomPadding() {
        return mBottomPadding;
    }

    @Override
    public int getEllipsizedWidth() {
        return mEllipsizedWidth;
    }

    private static class ChangeWatcher
    implements TextWatcher, SpanWatcher
    {
        public ChangeWatcher(DynamicLayout layout) {
            mLayout = new WeakReference(layout);
        }

        private void reflow(CharSequence s, int where, int before, int after) {
            DynamicLayout ml = (DynamicLayout) mLayout.get();

            if (ml != null)
                ml.reflow(s, where, before, after);
            else if (s instanceof Spannable)
                ((Spannable) s).removeSpan(this);
        }

        public void beforeTextChanged(CharSequence s,
                                      int where, int before, int after) {
            ;
        }

        public void onTextChanged(CharSequence s,
                                  int where, int before, int after) {
            reflow(s, where, before, after);
        }

        public void afterTextChanged(Editable s) {
            ;
        }

        public void onSpanAdded(Spannable s, Object o, int start, int end) {
            if (o instanceof UpdateLayout)
                reflow(s, start, end - start, end - start);
        }

        public void onSpanRemoved(Spannable s, Object o, int start, int end) {
            if (o instanceof UpdateLayout)
                reflow(s, start, end - start, end - start);
        }

        public void onSpanChanged(Spannable s, Object o, int start, int end,
                                  int nstart, int nend) {
            if (o instanceof UpdateLayout) {
                reflow(s, start, end - start, end - start);
                reflow(s, nstart, nend - nstart, nend - nstart);
            }
        }

        private WeakReference mLayout;
    }

    public int getEllipsisStart(int line) {
        if (mEllipsizeAt == null) {
            return 0;
        }

        return mInts.getValue(line, ELLIPSIS_START);
    }

    public int getEllipsisCount(int line) {
        if (mEllipsizeAt == null) {
            return 0;
        }

        return mInts.getValue(line, ELLIPSIS_COUNT);
    }

    private CharSequence mBase;
    private CharSequence mDisplay;
    private ChangeWatcher mWatcher;
    private boolean mIncludePad;
    private boolean mEllipsize;
    private int mEllipsizedWidth;
    private TextUtils.TruncateAt mEllipsizeAt;

    private PackedIntVector mInts;
    private PackedObjectVector<Directions> mObjects;

    private int mTopPadding, mBottomPadding;

    private static StaticLayout sStaticLayout = new StaticLayout(true);
    private static Object sLock = new Object();

    private static final int START = 0;
    private static final int DIR = START;
    private static final int TAB = START;
    private static final int TOP = 1;
    private static final int DESCENT = 2;
    private static final int COLUMNS_NORMAL = 3;

    private static final int ELLIPSIS_START = 3;
    private static final int ELLIPSIS_COUNT = 4;
    private static final int COLUMNS_ELLIPSIZE = 5;

    private static final int START_MASK = 0x1FFFFFFF;
    private static final int DIR_MASK   = 0xC0000000;
    private static final int DIR_SHIFT  = 30;
    private static final int TAB_MASK   = 0x20000000;

    private static final int ELLIPSIS_UNDEFINED = 0x80000000;
}