使用LevelListDrawable实现Html.fromHtml多张图片显示

首先一段html字符串

String source = "this is a test of <b>ImageGetter</b> it contains " +
                "two images: <br/>" +
                "<img src=\"http://developer.android.com/assets/images/dac_logo.png\"><br/>and<br/>" +
                "<img src=\"http://developer.android.com/assets/images/icon_search.png\">";

然后ImageGetter里面的getDrawable（String souce）方法里面实现

 LevelListDrawable d = new LevelListDrawable();
 rawable empty = getResources().getDrawable(R.drawable.ic_launcher);
        d.addLevel(0, 0, empty);
        d.setBounds(0, 0, empty.getIntrinsicWidth(), empty.getIntrinsicHeight());


        new LoadImage().execute(source, d);

这里的LodImage类是一个异步加载类，详见代码了

 class LoadImage extends AsyncTask<Object, Void, Bitmap> {

        private LevelListDrawable mDrawable;

        @Override
        protected Bitmap doInBackground(Object... params) {
            String source = (String) params[0];
            mDrawable = (LevelListDrawable) params[1];
            Log.d(TAG, "doInBackground " + source);
            try {
                InputStream is = new URL(source).openStream();
                return BitmapFactory.decodeStream(is);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            Log.d(TAG, "onPostExecute drawable " + mDrawable);
            Log.d(TAG, "onPostExecute bitmap " + bitmap);
            if (bitmap != null) {
                BitmapDrawable d = new BitmapDrawable(bitmap);
                mDrawable.addLevel(1, 1, d);
                mDrawable.setBounds(0, 0, bitmap.getWidth(), bitmap.getHeight());
                mDrawable.setLevel(1);
                // i don't know yet a better way to refresh TextView
                // mTv.invalidate() doesn't work as expected
                CharSequence t = mTv.getText();
                mTv.setText(t);
            }
        }
    }

目前还不是很了解这个LevelListDrawable，不知道这个 addLevel (int low, int high,  Drawable  drawable)里的low和hight有什么用途，但是官网有个例子

 <level-list xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:maxLevel="0" android:drawable="@drawable/ic_wifi_signal_1" />
   <item android:maxLevel="1" android:drawable="@drawable/ic_wifi_signal_2" />
   <item android:maxLevel="2" android:drawable="@drawable/ic_wifi_signal_3" />
   <item android:maxLevel="3" android:drawable="@drawable/ic_wifi_signal_4" />
  </level-list>

可能和这里的maxLevel有关，官网说android的手机充电的效果图就是使用这个类实现的，然后循环实现LevelListDrawable.setLevel(int)方法的。