Android example source code file (LeadingMarginSpan.java)

This example Android source code file (LeadingMarginSpan.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, charsequence, drawing, graphics, layout, leadingmarginspan, leadingmarginspan2, os, paint, paragraphstyle, parcelablespan, standard, text, ui, wraptogetherspan

The LeadingMarginSpan.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.style;

import android.graphics.Paint;
import android.graphics.Canvas;
import android.os.Parcel;
import android.text.Layout;
import android.text.ParcelableSpan;
import android.text.TextUtils;

/**
 * A paragraph style affecting the leading margin. There can be multiple leading
 * margin spans on a single paragraph; they will be rendered in order, each
 * adding its margin to the ones before it. The leading margin is on the right
 * for lines in a right-to-left paragraph.
 */
public interface LeadingMarginSpan
extends ParagraphStyle
{
    /**
     * Returns the amount by which to adjust the leading margin. Positive values
     * move away from the leading edge of the paragraph, negative values move
     * towards it.
     * 
     * @param first true if the request is for the first line of a paragraph,
     * false for subsequent lines
     * @return the offset for the margin.
     */
    public int getLeadingMargin(boolean first);

    /**
     * Renders the leading margin.  This is called before the margin has been
     * adjusted by the value returned by {@link #getLeadingMargin(boolean)}.
     * 
     * @param c the canvas
     * @param p the paint. The this should be left unchanged on exit.
     * @param x the current position of the margin
     * @param dir the base direction of the paragraph; if negative, the margin
     * is to the right of the text, otherwise it is to the left.
     * @param top the top of the line
     * @param baseline the baseline of the line
     * @param bottom the bottom of the line
     * @param text the text
     * @param start the start of the line
     * @param end the end of the line
     * @param first true if this is the first line of its paragraph
     * @param layout the layout containing this line
     */
    public void drawLeadingMargin(Canvas c, Paint p,
                                  int x, int dir,
                                  int top, int baseline, int bottom,
                                  CharSequence text, int start, int end,
                                  boolean first, Layout layout);


    /**
     * An extended version of {@link LeadingMarginSpan}, which allows
     * the implementor to specify the number of lines of text to which
     * this object is attached that the "first line of paragraph" margin
     * width will be applied to.
     */
    public interface LeadingMarginSpan2 extends LeadingMarginSpan, WrapTogetherSpan {
        /**
         * Returns the number of lines of text to which this object is
         * attached that the "first line" margin will apply to.
         * Note that if this returns N, the first N lines of the region,
         * not the first N lines of each paragraph, will be given the
         * special margin width.
         */
        public int getLeadingMarginLineCount();
    };

    /**
     * The standard implementation of LeadingMarginSpan, which adjusts the
     * margin but does not do any rendering.
     */
    public static class Standard implements LeadingMarginSpan, ParcelableSpan {
        private final int mFirst, mRest;
        
        /**
         * Constructor taking separate indents for the first and subsequent
         * lines.
         * 
         * @param first the indent for the first line of the paragraph
         * @param rest the indent for the remaining lines of the paragraph
         */
        public Standard(int first, int rest) {
            mFirst = first;
            mRest = rest;
        }

        /**
         * Constructor taking an indent for all lines.
         * @param every the indent of each line
         */
        public Standard(int every) {
            this(every, every);
        }

        public Standard(Parcel src) {
            mFirst = src.readInt();
            mRest = src.readInt();
        }
        
        public int getSpanTypeId() {
            return TextUtils.LEADING_MARGIN_SPAN;
        }
        
        public int describeContents() {
            return 0;
        }

        public void writeToParcel(Parcel dest, int flags) {
            dest.writeInt(mFirst);
            dest.writeInt(mRest);
        }

        public int getLeadingMargin(boolean first) {
            return first ? mFirst : mRest;
        }

        public void drawLeadingMargin(Canvas c, Paint p,
                                      int x, int dir,
                                      int top, int baseline, int bottom,
                                      CharSequence text, int start, int end,
                                      boolean first, Layout layout) {
            ;
        }
    }
}