Android example source code file (DynamicDrawableSpan.java)

This example Android source code file (DynamicDrawableSpan.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

align_baseline, align_bottom, android, charsequence, drawable, drawing, dynamicdrawablespan, graphics, override, paint, rect, replacementspan, string, tag, ui, util, weakreference

The DynamicDrawableSpan.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.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Paint.Style;
import android.graphics.drawable.Drawable;
import android.util.Log;

import java.lang.ref.WeakReference;

/**
 *
 */
public abstract class DynamicDrawableSpan extends ReplacementSpan {
    private static final String TAG = "DynamicDrawableSpan";
    
    /**
     * A constant indicating that the bottom of this span should be aligned
     * with the bottom of the surrounding text, i.e., at the same level as the
     * lowest descender in the text.
     */
    public static final int ALIGN_BOTTOM = 0;
    
    /**
     * A constant indicating that the bottom of this span should be aligned
     * with the baseline of the surrounding text.
     */
    public static final int ALIGN_BASELINE = 1;
    
    protected final int mVerticalAlignment;
    
    public DynamicDrawableSpan() {
        mVerticalAlignment = ALIGN_BOTTOM;
    }

    /**
     * @param verticalAlignment one of {@link #ALIGN_BOTTOM} or {@link #ALIGN_BASELINE}.
     */
    protected DynamicDrawableSpan(int verticalAlignment) {
        mVerticalAlignment = verticalAlignment;
    }

    /**
     * Returns the vertical alignment of this span, one of {@link #ALIGN_BOTTOM} or
     * {@link #ALIGN_BASELINE}.
     */
    public int getVerticalAlignment() {
        return mVerticalAlignment;
    }

    /**
     * Your subclass must implement this method to provide the bitmap   
     * to be drawn.  The dimensions of the bitmap must be the same
     * from each call to the next.
     */
    public abstract Drawable getDrawable();

    @Override
    public int getSize(Paint paint, CharSequence text,
                         int start, int end,
                         Paint.FontMetricsInt fm) {
        Drawable d = getCachedDrawable();
        Rect rect = d.getBounds();

        if (fm != null) {
            fm.ascent = -rect.bottom; 
            fm.descent = 0; 

            fm.top = fm.ascent;
            fm.bottom = 0;
        }

        return rect.right;
    }

    @Override
    public void draw(Canvas canvas, CharSequence text,
                     int start, int end, float x, 
                     int top, int y, int bottom, Paint paint) {
        Drawable b = getCachedDrawable();
        canvas.save();
        
        int transY = bottom - b.getBounds().bottom;
        if (mVerticalAlignment == ALIGN_BASELINE) {
            transY -= paint.getFontMetricsInt().descent;
        }

        canvas.translate(x, transY);
        b.draw(canvas);
        canvas.restore();
    }

    private Drawable getCachedDrawable() {
        WeakReference<Drawable> wr = mDrawableRef;
        Drawable d = null;

        if (wr != null)
            d = wr.get();

        if (d == null) {
            d = getDrawable();
            mDrawableRef = new WeakReference<Drawable>(d);
        }

        return d;
    }

    private WeakReference<Drawable> mDrawableRef;
}