ListView中的图片优化（异步加载，内存缓存图片-软引用）
软引用-SoftReference
 |
| 1、定义软引用 /**
* key:图片的名字
* value:软引用的bitmap
*/
private Map<String, SoftReference<Bitmap>> iconCacheMap;2、初始化 iconCacheMap = new HashMap<String, SoftReference<Bitmap>>(); |
| 3、使用 /**
* listview数据填充类
*/
private class MyReadAdapter extends BaseAdapter {
private final List<Book> books;
public MyReadAdapter(List<Book> books) {
this.books = books;
}
@Override
public int getCount() {
return books.size();
}
@Override
public Object getItem(int position) {
return books.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView != null && convertView instanceof LinearLayout) {
holder = (ViewHolder) convertView.getTag();
} else {
holder = new ViewHolder();
convertView = View.inflate(MyReadActivity.this,R.layout.book_item, null);
//holder.ivBbook = (ImageView) convertView.findViewById(R.id.book_img);
holder.tvTitle = (TextView) convertView.findViewById(R.id.book_title);
holder.tvDescription = (TextView) convertView.findViewById(R.id.book_description);
holder.rbRate = (RatingBar) convertView.findViewById(R.id.ratingbar);
convertView.setTag(holder);
}
Book book = books.get(position);
// 书名
holder.tvTitle.setText(book.getName());
// 书的描述
holder.tvDescription.setText(book.getDescription());
// 书的评价
if (book.getRating() != 0) {
holder.rbRate.setRating(book.getRating());
} else {
holder.rbRate.setVisibility(View.INVISIBLE);
}
// 书的图片-图片的异步加载
final ImageView ivBbook = (ImageView) convertView.findViewById(R.id.book_img);
String filePath = book.getBookurl();
// 获得文件名
final String fileName = filePath.substring(filePath.lastIndexOf("/") + 1, filePath.length());
// 1、图片保存在sd卡上，从sd卡上获取
// // 判断是否在sd卡有该图片
// String storageState = Environment.getExternalStorageState();
// File file = null;
// if (Environment.MEDIA_MOUNTED.equals(storageState)) {
// file = new File(Environment.getExternalStorageDirectory(),fileName);
// }
// if (file != null && file.exists()) {// /图片在sd卡有保存
// ivBbook.setImageURI(Uri.fromFile(file));
// Log.i(TAG, "从sd卡获取图片：" + fileName);
// } else {// 图片文件不在sk卡保存
// loadImage(ivBbook, filePath, fileName);
// }
// 2、图片保存在内存中，从内存中获取
if (iconCacheMap.containsKey(fileName)) {
SoftReference<Bitmap> reference = iconCacheMap.get(fileName);
if (reference != null) {
Bitmap bitmap = reference.get();
if (bitmap != null) {// 内存中该bitmap的缓存还没有被gc回收，那么复用
ivBbook.setImageBitmap(bitmap);
Log.i(TAG, "从内存中获取图片" + fileName);
} else {
loadImage(ivBbook, filePath, fileName);
}
}
} else {
loadImage(ivBbook, filePath, fileName);
}
return convertView;
}
/**
* 异步获取图片
*
* @param ivBbook
* @param filePath
* @param fileName
*/
private void loadImage(final ImageView ivBbook, String filePath,
final String fileName) {
new LoadImageAsynTask<String, Void, Bitmap>(new LoadImageAsynTaskCallback<Bitmap>() {
@Override
public void beforeLoadImage() {
ivBbook.setImageResource(R.drawable.ic_launcher);
}
@Override
public void afterLoadImage(Bitmap bitmap) {
if (bitmap!=null) {
Log.i(TAG, "从服务器上下载图片"+fileName);
ivBbook.setImageBitmap(bitmap);
// //1、保存bitmap到sd卡上
// try {
//
// //判断sd卡状态
// String storageState = Environment.getExternalStorageState();
// File file = null;
// if (Environment.MEDIA_MOUNTED.equals(storageState)) {
// file = new File(Environment.getExternalStorageDirectory(),fileName);
// }else {
// return;
// }
// CompressFormat format = CompressFormat.JPEG;
// int quality = 100;//100无损保存
// OutputStream stream = new FileOutputStream(file);
// boolean b = bitmap.compress(format , quality , stream );
// Log.i(TAG, "保存图片"+fileName+"到sd卡："+b);
// } catch (FileNotFoundException e) {
// e.printStackTrace();
// }
//2、保存到内存-软引用
SoftReference<Bitmap> value = new SoftReference<Bitmap>(bitmap);
iconCacheMap.put(fileName, value);
Log.i(TAG, "保存图片"+fileName+"到内存");
}else {
ivBbook.setImageResource(R.drawable.ic_launcher);
}
}
}){
@Override
protected Bitmap doInBackground(String... params) {
try {
URL url = new URL(params[0]);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
InputStream is = conn.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(is);
return bitmap;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}.execute(filePath);
}
}
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结果： |