AsynTast异步加载图片.doc

AsyncTast加载本地图片AsyncTask不只是可以用来异步加载图片，还可以异步做很多的任务，只要是耗时的操作都可以写到doInBackground()方法里面，在onpostExcute()方法里面更新ui界面。AyncTast加载本地图片：class loadImage extends AsyncTaskOverride protected Object doInBackground(Object. params)Bitmap img_head = null;imgs = new ArrayList();Cursor c=mcr.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,new String * , null, null, null);while (c.moveToNext() String title=c.getString(c.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME);/ 图片全名String path = c.getString(c.getColumnIndex(MediaStore.Images.Media.DATA);Int size=c.getInt(c.getColumnIndex(MediaStore.Images.Media.SIZE);Bitmap img_head = getImageThumbnail(path, 70, 70);Image img = new Image(title, path, size, img_head);publishProgress(img);c.close();Return null; private Bitmap getImageThumbnail(String imagePath, int width, int height) Bitmap bitmap = null;BitmapFactory.Options options=new BitmapFactory.Options();options.inJustDecodeBounds = true;/ 获取这个图片的宽和高，注意此处的bitmap为nullbitmap = BitmapFactory.decodeFile(imagePath, options);options.inJustDecodeBounds = false; / 设为 false/ 计算缩放比int h = options.outHeight;int w = options.outWidth;int beWidth = w / width;int beHeight = h / height;int be = 1;if (beWidth beHeight) be = beWidth; else be = beHeight;if (be = 0) be = 1;options.inSampleSize = be;/ 重新读入图片，读取缩放后的bitmap，注意这次要把options.inJustDecodeBounds 设为 falsebitmap = BitmapFactory.decodeFile(imagePath, options);/ 利用ThumbnailUtils来创建缩略图，这里要指定要缩放哪个Bitmap对象bitmap = ThumbnailUtils.extractThumbnail(bitmap, width, height,ThumbnailUtils.OPTIONS_RECYCLE_INPUT);return bitmap;Overrideprotected void onProgressUpdate(Image. values) super.onProgressUpdate(values); Overrideprotected void onPostExecute(Object result) / TODO Auto-generated meth