TextViewMultilineEllipse.java

/**
 * Copyright 2009 Mark Wyszomierski
 *
 * 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 com.markww.test;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint.Align;
import android.text.TextPaint;
import android.view.View;


/**
 * Provides a simple TextView-like control which allows us to set a max number
 * of lines to wrap an input string, then ellipsizes the last line if there's
 * not enough room to handle the entire input string.
 * 
 * This widget can be in a collapsed or expanded mode. In collapsed mode, the
 * maxLines parameter is honored, and ellipsizing will occur if there's not
 * enough space for the input string. In expanded mode, the widget takes up
 * as much height as necessary for the input string. You can toggle the mode
 * to expand/collapse the widget in-place, via a click-handler for example.
 * 
 * This widget does not handle right to left text, spannables, it's pretty
 * basic.
 * 
 * The basis for this widget is taken from the android custom widget doc:
 * http://developer.android.com/guide/samples/ApiDemos/src/com/example/android/apis/view/LabelView.html
 * 
 * @author Mark Wyszomierski
 */
public class TextViewMultilineEllipse extends View 
{
    private TextPaint mTextPaint;
    private String mText;
    private int mAscent;
    private String mStrEllipsis;
    private String mStrEllipsisMore;
    private int mMaxLines;
    private boolean mDrawEllipsizeMoreString;
    private int mColorEllipsizeMore;
    private boolean mRightAlignEllipsizeMoreString;
    private boolean mExpanded;
    private LineBreaker mBreakerExpanded;
    private LineBreaker mBreakerCollapsed;
    

    
    public TextViewMultilineEllipse(Context context) {
        super(context);
        
        mExpanded = false;
        mDrawEllipsizeMoreString = true;
        mRightAlignEllipsizeMoreString = false;
        mMaxLines = -1;
        mStrEllipsis = "...";
        mStrEllipsisMore = "";
        mColorEllipsizeMore = 0xFF0000FF;

        mBreakerExpanded = new LineBreaker();        
        mBreakerCollapsed = new LineBreaker();
        
        // Default font size and color.
        mTextPaint = new TextPaint();
        mTextPaint.setAntiAlias(true);
        mTextPaint.setTextSize(13);
        mTextPaint.setColor(0xFF000000);
        mTextPaint.setTextAlign(Align.LEFT);
    } 
    
    /**
     * Sets the text to display in this widget.
     * @param text The text to display.
     */
    public void setText(String text) {
        mText = text;
        requestLayout();
        invalidate();
    }

    /**
     * Sets the text size for this widget.
     * @param size Font size.
     */
    public void setTextSize(int size) {
        mTextPaint.setTextSize(size);
        requestLayout();
        invalidate();
    }

    /**
     * Sets the text color for this widget.
     * @param color ARGB value for the text.
     */
    public void setTextColor(int color) {
        mTextPaint.setColor(color);
        invalidate();
    }

    /**
     * The string to append when ellipsizing. Must be shorter than the available
     * width for a single line!
     * @param ellipsis The ellipsis string to use, like "...", or "-----".
     */
    public void setEllipsis(String ellipsis) {
        mStrEllipsis = ellipsis;
    }
    
    /**
     * Optional extra ellipsize string. This
     * @param ellipsisMore
     */
    public void setEllipsisMore(String ellipsisMore) {
        mStrEllipsisMore = ellipsisMore;
    }
    
    /**
     * The maximum number of lines to allow, height-wise.
     * @param maxLines
     */
    public void setMaxLines(int maxLines) {
        mMaxLines = maxLines;
    }
    
    /**
     * Turn drawing of the optional ellipsizeMore string on or off.
     * @param drawEllipsizeMoreString Yes or no.
     */
    public void setDrawEllipsizeMoreString(boolean drawEllipsizeMoreString) {
        mDrawEllipsizeMoreString = drawEllipsizeMoreString;
    }
    
    /**
     * Font color to use for the optional ellipsizeMore string.
     * @param color ARGB color.
     */
    public void setColorEllpsizeMore(int color) {
        mColorEllipsizeMore = color;
    }
    
    /**
     * When drawing the ellipsizeMore string, either draw it wherever ellipsizing on the last
     * line occurs, or always right align it. On by default.
     * @param rightAlignEllipsizeMoreString Yes or no.
     */
    public void setRightAlignEllipsizeMoreString(boolean rightAlignEllipsizeMoreString) {
        mRightAlignEllipsizeMoreString = rightAlignEllipsizeMoreString;
    }
    
    /**
     * @see android.view.View#measure(int, int)
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(
            measureWidth(widthMeasureSpec),
            measureHeight(heightMeasureSpec));
    }

    /**
     * Determines the width of this view
     * @param measureSpec A measureSpec packed into an int
     * @return The width of the view, honoring constraints from measureSpec
     */
    private int measureWidth(int measureSpec) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        if (specMode == MeasureSpec.EXACTLY) {
            // We were told how big to be.
            result = specSize;
            
            // Format the text using this exact width, and the current mode.
            breakWidth(specSize);
        } 
        else {
            if (specMode == MeasureSpec.AT_MOST) {
                // Use the AT_MOST size - if we had very short text, we may need even less
                // than the AT_MOST value, so return the minimum.
                result = breakWidth(specSize);
                result = Math.min(result, specSize);
            }
            else {
                // We're not given any width - so in this case we assume we have an unlimited
                // width?
                breakWidth(specSize);
            }
        }

        return result;
    }

    /**
     * Determines the height of this view
     * @param measureSpec A measureSpec packed into an int
     * @return The height of the view, honoring constraints from measureSpec
     */
    private int measureHeight(int measureSpec) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        mAscent = (int) mTextPaint.ascent();
        if (specMode == MeasureSpec.EXACTLY) {
            // We were told how big to be, so nothing to do.
            result = specSize;
        } 
        else {
            // The lines should already be broken up. Calculate our max desired height
            // for our current mode.
            int numLines;
            if (mExpanded) {
                numLines = mBreakerExpanded.getLines().size();
            }
            else {
                numLines = mBreakerCollapsed.getLines().size();
            }
            result = numLines * (int) (-mAscent + mTextPaint.descent())
                   + getPaddingTop()
                   + getPaddingBottom();

            // Respect AT_MOST value if that was what is called for by measureSpec.
            if (specMode == MeasureSpec.AT_MOST) {
                result = Math.min(result, specSize);
            }
        }
        return result;
    }

    /**
     * Render the text
     * 
     * @see android.view.View#onDraw(android.graphics.Canvas)
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        
        List<int[]> lines;
        LineBreaker breaker;
        if (mExpanded) {
            breaker = mBreakerExpanded;
            lines = mBreakerExpanded.getLines();
        }
        else {
            breaker = mBreakerCollapsed;
            lines = mBreakerCollapsed.getLines();
        }
        
        float x = getPaddingLeft();
        float y = getPaddingTop() + (-mAscent);
        for (int i = 0; i < lines.size(); i++) {
            // Draw the current line.
            int[] pair = lines.get(i);
            canvas.drawText(mText, pair[0], pair[1]+1, x, y, mTextPaint);
            
            // Draw the ellipsis if necessary.
            if (i == lines.size() - 1) {
                if (breaker.getRequiredEllipsis()) {
                    canvas.drawText(mStrEllipsis, x + breaker.getLengthLastEllipsizedLine(), y, mTextPaint);
                    if (mDrawEllipsizeMoreString) {
                        int lastColor = mTextPaint.getColor();
                        mTextPaint.setColor(mColorEllipsizeMore);
                        if (mRightAlignEllipsizeMoreString) {
                            // Seems to not be right...
                            canvas.drawText(mStrEllipsisMore, canvas.getWidth()-(breaker.getLengthEllipsisMore()+getPaddingRight()+getPaddingLeft()), y, mTextPaint);
                        }
                        else {
                            canvas.drawText(mStrEllipsisMore, x + breaker.getLengthLastEllipsizedLinePlusEllipsis(), y, mTextPaint);
                        }
                        mTextPaint.setColor(lastColor);
                    }
                }
            }
            
            y += (-mAscent + mTextPaint.descent());
            if (y > canvas.getHeight()) {
                break;
            }
        }
    }
    
    public boolean getIsExpanded() {
        return mExpanded;
    }
    
    public void expand() {
        mExpanded = true;
        requestLayout();
        invalidate();
    }
    
    public void collapse() {
        mExpanded = false;
        requestLayout();
        invalidate();
    }
    
    private int breakWidth(int availableWidth) {
        int widthUsed = 0;
        if (mExpanded) {
            widthUsed =
              mBreakerExpanded.breakText(
                 mText, 
                availableWidth - getPaddingLeft() - getPaddingRight(), 
                mTextPaint);
        }
        else {
            widthUsed =
              mBreakerCollapsed.breakText(
                mText, 
                mStrEllipsis, 
                mStrEllipsisMore, 
                mMaxLines, 
                availableWidth - getPaddingLeft() - getPaddingRight(), 
                mTextPaint);
        }
        
        return widthUsed + getPaddingLeft() + getPaddingRight();
    }
    
    
    /**
     * Used internally to break a string into a list of integer pairs. The pairs are
     * start and end locations for lines given the current available layout width.
     */
    private static class LineBreaker
    {
        /** Was the input text long enough to need an ellipsis? */
        private boolean mRequiredEllipsis;
        
        /** Beginning and end indices for the input string. */
        private ArrayList<int[]> mLines;
        
        /** The width in pixels of the last line, used to draw the ellipsis if necessary. */
        private float mLengthLastLine;
        
        /** The width of the ellipsis string, so we know where to draw the ellipsisMore string
         *  if necessary.
         */
        private float mLengthEllipsis;
        
        /** The width of the ellipsizeMore string, same use as above. */
        private float mLengthEllipsisMore;
        
        
        public LineBreaker() {
            mRequiredEllipsis = false;
            mLines = new ArrayList<int[]>();
        }

        /**
         * Used for breaking text in 'expanded' mode, which needs no ellipse.
         * Uses as many lines as is necessary to accomodate the entire input
         * string.
         * @param input String to be broken.
         * @param maxWidth Available layout width.
         * @param tp Current paint object with styles applied to it.
         */
        public int breakText(String input, 
                                int maxWidth, 
                             TextPaint tp) 
        {
            return breakText(input, null, null, -1, maxWidth, tp);
        }

        /**
         * Used for breaking text, honors ellipsizing. The string will be broken into lines using
         * the available width. The last line will subtract the physical width of the ellipsis
         * string from maxWidth to reserve room for the ellipsis. If the ellpsisMore string is set,
         * then space will also be reserved for its length as well.
         * @param input String to be broken.
         * @param ellipsis Ellipsis string, like "..."
         * @param ellipsisMore Optional space reservation after the ellipsis, like " Read More!"
         * @param maxLines Max number of lines to allow before ellipsizing.
         * @param maxWidth Available layout width.
         * @param tp Current paint object with styles applied to it.
         */
        public int breakText(String input, 
                                String ellipsis,
                                String ellipsisMore,
                             int maxLines, 
                             int maxWidth, 
                             TextPaint tp) 
        {
            mLines.clear();
            mRequiredEllipsis = false;
            mLengthLastLine = 0.0f;
            mLengthEllipsis = 0.0f;
            mLengthEllipsisMore = 0.0f;
            
            // If maxWidth is -1, interpret that as meaning to render the string on a single
            // line. Skip everything.
            if (maxWidth == -1) {
                mLines.add(new int[] { 0, input.length() });
                return (int)(tp.measureText(input) + 0.5f);
            }

            // Measure the ellipsis string, and the ellipsisMore string if valid.
            if (ellipsis != null) {
                mLengthEllipsis = tp.measureText(ellipsis);
            }
            if (ellipsisMore != null) {
                mLengthEllipsisMore = tp.measureText(ellipsisMore);
            }

            // Start breaking.
            int posStartThisLine = -1;
            float lengthThisLine = 0.0f;
            boolean breakWords = true;
            int pos = 0;
            while (pos < input.length()) {
                
                if (posStartThisLine == -1) {
                    posStartThisLine = pos;
                }
                
                if (mLines.size() == maxLines) {
                    mRequiredEllipsis = true;
                    break;
                }
                
                float widthOfChar = tp.measureText(input.charAt(pos) + "");
                boolean newLineRequired = false;
                
                // Check for a new line character or if we've run over max width.
                if (input.charAt(pos) == '\n') {
                    newLineRequired = true;
                    
                    // We want the current line to go up to the character right before the
                    // new line char, and we want the next line to start at the char after
                    // this new line char.
                    mLines.add(new int[] { posStartThisLine, pos-1 });
                }
                else if (lengthThisLine + widthOfChar >= maxWidth) {
                    newLineRequired = true;
                    // We need to backup if we are in the middle of a word.
                    if (input.charAt(pos) == ' ' || breakWords == false) {
                        // Backup one character, because it doesn't fit on this line.
                        pos--;

                        // So this line includes up to the character before the space.
                        mLines.add(new int[] { posStartThisLine, pos });
                    }
                    else {
                        // Backup until we are at a space.
                        while (input.charAt(pos) != ' ') {
                            pos--;
                        }
                        
                        // This line includes up to the space.
                        mLines.add(new int[] { posStartThisLine, pos });
                    }
                }
                
                if (newLineRequired) {
                    // The next cycle should reset the position if it sees it's -1 (to whatever i is).
                    posStartThisLine = -1;
                    
                    // Reset line length for next iteration.
                    lengthThisLine = 0.0f;
                    
                    // When we get to the last line, subtract the width of the ellipsis.
                    if (mLines.size() == maxLines - 1) {
                        maxWidth -= (mLengthEllipsis + mLengthEllipsisMore);
                        // We also don't need to break on a full word, it'll look a little
                        // cleaner if all breaks on the final lines break in the middle of
                        // the last word.
                        breakWords = false;
                    }
                }
                else {
                    lengthThisLine += widthOfChar;
                    
                    // If we're on the last character of the input string, add on whatever we have leftover.
                    if (pos == input.length() - 1) {
                        mLines.add(new int[] { posStartThisLine, pos });
                    }
                }
                
                pos++;
            }
            
            // If we ellipsized, then add the ellipsis string to the end.
            if (mRequiredEllipsis) {
                int[] pairLast = mLines.get(mLines.size()-1);
                mLengthLastLine = tp.measureText(input.substring(pairLast[0], pairLast[1] + 1));
            }
            
            // If we required only one line, return its length, otherwise we used
            // whatever the maxWidth supplied was.
            if (mLines.size() == 0) {
                return 0;
            }
            else if (mLines.size() == 1) {
                return (int)(tp.measureText(input) + 0.5f);
            }
            else {
                return maxWidth;
            }
        }
        
        public boolean getRequiredEllipsis() {
            return mRequiredEllipsis;
        }
        
        public List<int[]> getLines() {
            return mLines;
        }
        
        public float getLengthLastEllipsizedLine() {
            return mLengthLastLine;
        }
        
        public float getLengthLastEllipsizedLinePlusEllipsis() {
            return mLengthLastLine + mLengthEllipsis;
        }
        
        public float getLengthEllipsis() {
            return mLengthEllipsis;
        }
        
        public float getLengthEllipsisMore() {
            return mLengthEllipsisMore;
        }
    }
}