taglayout.java

有关j2me的很好的例子可以研究一下

            // while odd numbers are Item's content (text or image)
            if ((i % 2) == 0) {
                obj = item.getLabel();
                
                // Insert a new line if Label does not start
                // on a new line
                if (obj != null && !((String)obj).equals("") 
                    && curWidth != 0) {

                    lastIndex = addBreak((short)i, (short)0, lastIndex);
                    numLines++;
                    
                    curWidth = 0; 
                }

            } else {                  
                if (item instanceof StringItem) {
                    obj = ((StringItem)item).getText();
                } else if (item instanceof ImageItem) {
                    obj = ((ImageItem)item).getImage();
                }
            }
            if (obj == null) {
                continue;
            }

            // Next object to be laid out is an Image
            if (obj instanceof Image) {
                Image img      = (Image)obj;
                int imgWidth   = img.getWidth();
                int imgHeight  = img.getHeight();
                int layout     = ((ImageItem)item).getLayout();

                // new line before image should be added if image does not
                // fit on this line or if LAYOUT_NEWLINE_BEFORE was set
                // in Item's layout
                boolean addNewLineBefore = 
                    (((layout & ImageItem.LAYOUT_NEWLINE_BEFORE) != 0) ||
                         (curWidth + imgWidth > width));

                // new line before image should be added 
                // if LAYOUT_NEWLINE_AFTER was set in Item's layout and this
                // is not the last image on this layout
                boolean addNewLineAfter =
                    (((layout & ImageItem.LAYOUT_NEWLINE_AFTER) != 0) && 
                     (i < 2*numItems-1));
                if (!addNewLineBefore && !addNewLineAfter) {
                    curWidth += imgWidth;
                }

                // add line breaks if new line has to be added before, or
                // after, or if image is taller than the lineHeight
                if (addNewLineBefore || addNewLineAfter ||
                    imgHeight > lineHeight) {
                    
                    int heightOffset = 0;
                    if ((addNewLineBefore && curWidth == 0) ||
                        !addNewLineBefore) {
                        heightOffset = lineHeight;
                    }

                    for (; heightOffset < imgHeight;
                         heightOffset += lineHeight) {
                        lastIndex = addBreak((short)i, (short)heightOffset,
                                             lastIndex);
                        numLines++;
                    }

                    if (addNewLineAfter) {
                        lastIndex = addBreak((short)(i+1), (short)0,
                                             lastIndex);
                        
                        numLines++;
                        curWidth = 0;

                    } else if (addNewLineBefore) {

                        curWidth = imgWidth;
                    }
                }

            } else if (obj instanceof String) { // Text

                // Next object to be laid out is an Image
                String str = (String)obj;
                int strLength = str.length();

                if (strLength == 0) continue;

                int wordWidth  = 0;
                int spaceIndex = -1;

                /*
                int curStart = fromLine == numLines-1 ? 
                               lineBreaks[lastInfo-1] : 0;
                               */
                for (int j = 0; j < strLength; j++) {

                    char ch = str.charAt(j);
                    int charWidth = f.charWidth(ch);

                    // add a line break if next character is '\n';
                    // if this is the last character in this string
                    // then first element on the next line will be
                    // with a 0 offset, otherwise it will be next character
                    if (ch == '\n') {
                        if (j == strLength-1) {
                            lastIndex = addBreak((short)(i+1), (short)0, 
                                                 lastIndex);
                        } else {
                            lastIndex = addBreak((short)i, (short)(j+1),
                                                 lastIndex);
                        }
                        numLines++;
                        curWidth = wordWidth = 0;
                        spaceIndex = -1;
                        
                        continue;
                    }
                    
                    if (ch == ' ') {
                        spaceIndex = j;
                        wordWidth = 0;
                    } else {
                        wordWidth += charWidth;
                    }
                    curWidth += charWidth;

                    // add a line break at the last recoreded word break
                    // if next character does not fit on this line
                    if (curWidth > width) { 
                        
                        if (wordWidth > width) { // long word
                            lastIndex = addBreak((short)i, (short)j, 
                                                 lastIndex);
                            curWidth = wordWidth = charWidth;
                        } else {              // do word wrap
                            lastIndex = addBreak((short)i, 
                                                 (short)(spaceIndex+1),
                                                 lastIndex);
                            if (j == spaceIndex) {
                                wordWidth = 0;
                            }
                            curWidth = wordWidth;
                        }
                        numLines++;
                        spaceIndex = -1;
                    }
                }
            }
        }
        
        // always add the last break (for the last line)
        addBreak((short)(2*numItems), (short)0, lastIndex);
        numLines++;

        height = numLines * lineHeight;
        if (minHeight != -1 && height < minHeight) {
            height = minHeight;
        }

        if (maxHeight != -1 && height > maxHeight) {
            height = maxHeight;
        }

        // printLines();
    }

    /**
     * Update the content of this layout
     *
     * @param index The index of the Item to update
     * @return int The delta height change caused by the update
     */
    private int updateContent(int index) {

        // update lines array if it was set up already
        if (width <= 0) {
            return 0;
        }

        int oldHeight = height;

        if (index == 0 || numLines == 0) {

            updateLineBreaks(width);
            return height - oldHeight;

        }

        for (int line = 0; line < numLines; line++) {
            int nextIndex = line+1 < numLines ? 
                lineBreaks[line+1] : numItems;
            if (index > nextIndex) {
                if (line > 0) line--;
            }
            
            if (index >= nextIndex) {
                if (line > 0) line--;
                updateLineBreaks(/* line, */width);
                return height - oldHeight;
            }
        }

        updateLineBreaks(/* numLines-1, */ width);
        return height - oldHeight;
    }
    /*
    void printLines() {
        
        int next = 0;
        int nextIndex  = 0;
        int nextOffset = 0;

        System.err.println("\nPrintlines numLines=" +numLines+
                           " lineBreaks.length=" +lineBreaks.length+ 
                           " numItems=" +numItems+ 
                           " items.length=" +items.length);

        for (int j = nextIndex, offset = nextOffset; j < 2*numItems; ) {

            // move to the next subItem if the end of current item was painted
            if (j < nextIndex) {
                j++;
                if (j >= 2*numItems) {
                    break;
                }
                
                offset = 0;
            }

            // move to next line if the end of current line was reached
            if (j == nextIndex && offset == nextOffset) {
                if (next > 2*numLines) {
                    break;
                }

                nextIndex = lineBreaks[next++];
                nextOffset = lineBreaks[next++];
                
                System.err.println("Line: " +(next/2-1)+ 
                                   " index=" +(j/2)+
                                   " offset=" +offset+
                                   " nextIndex=" +nextIndex+
                                   " nextOffset=" +nextOffset);
            }
            
            Item item = items[j/2];            
            boolean isLabel = ((j%2) == 0);

            Object obj = null;

            if (isLabel) {
                obj = item.getLabel();
            } else {                  
                if (item instanceof StringItem) {
                    obj = ((StringItem)item).getText();
                } else if (item instanceof ImageItem) {
                    obj = ((ImageItem)item).getImage();
                }
            }
            
            if (obj == null) continue;

            if (obj instanceof Image) {
                Image img = (Image)obj;
                int imgHeight = img.getHeight();
                int layout = ((ImageItem)item).getLayout();
                String layoutStr = "(";
                if ((layout & ImageItem.LAYOUT_NEWLINE_BEFORE) != 0) {
                    layoutStr += "LAYOUT_NEWLINE_BEFORE ";
                }
                if ((layout & ImageItem.LAYOUT_NEWLINE_AFTER) != 0) {
                    layoutStr += "LAYOUT_NEWLINE_AFTER ";
                }                
                if ((layout & ImageItem.LAYOUT_DEFAULT) != 0) {
                    layoutStr += "LAYOUT_DEFAULT ";
                }
                if ((layout & ImageItem.LAYOUT_CENTER) != 0) {
                    layoutStr += "LAYOUT_CENTER ";
                }
                if ((layout & ImageItem.LAYOUT_LEFT) != 0) {
                    layoutStr += "LAYOUT_LEFT ";
                }
                if ((layout & ImageItem.LAYOUT_RIGHT) != 0) {
                    layoutStr += "LAYOUT_RIGHT ";
                }
                layoutStr += ")";
                System.err.println("\t Image: layout=" +layout+
                                   " j=" +j+ " index=" +(j/2)+ 
                                   " offset=" +offset+
                                   " layout=" +layoutStr);
                
                offset += lineHeight;

            } else if (obj instanceof String) {
                String str = (String)obj;
                int strLen = str.length();
                
                int endIndex = (j == nextIndex ? nextOffset : strLen); 

                System.err.print("\t" + (isLabel ? "Label" : "Text"));
                System.err.println(" (j=" +j+ " index=" +(j/2)+
                                   " offset=" +offset+ 
                                   " endIndex=" +endIndex+")='" +
                                   str.substring(offset, endIndex)+ 
                                   "'");
                offset = endIndex;
            }
        }
    } */
}