android/text/style/TabStopSpan.java

/*
 * 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.annotation.IntRange;
import android.annotation.Px;

/**
 * Paragraph affecting span that changes the position of the tab with respect to
 * the leading margin of the line. <code>TabStopSpan</code> will only affect the first tab
 * encountered on the first line of the text.
 */
public interface TabStopSpan extends ParagraphStyle {

    /**
     * Returns the offset of the tab stop from the leading margin of the line, in pixels.
     *
     * @return the offset, in pixels
     */
    int getTabStop();

    /**
     * The default implementation of TabStopSpan that allows setting the offset of the tab stop
     * from the leading margin of the first line of text.
     * <p>
     * Let's consider that we have the following text: <i>"\tParagraph text beginning with tab."</i>
     * and we want to move the tab stop with 100px. This can be achieved like this:
     * <pre>
     * SpannableString string = new SpannableString("\tParagraph text beginning with tab.");
     * string.setSpan(new TabStopSpan.Standard(100), 0, string.length(),
     * Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);</pre>
     * <img src="{@docRoot}reference/android/images/text/style/tabstopspan.png" />
     * <figcaption>Text with a tab stop and a <code>TabStopSpan</code></figcaption>
     */
    class Standard implements TabStopSpan {

        @Px
        private int mTabOffset;

        /**
         * Constructs a {@link TabStopSpan.Standard} based on an offset.
         *
         * @param offset the offset of the tab stop from the leading margin of
         *               the line, in pixels
         */
        public Standard(@IntRange(from = 0) int offset) {
            mTabOffset = offset;
        }

        @Override
        public int getTabStop() {
            return mTabOffset;
        }
    }
}