标签：android des style blog http color
本文内容
缩略图能减少手机内存的消耗。网络上的资源一般对手机来说，大了点，把图片解码，减少其尺寸，从而减少手机内存的消耗。
本文采用的歌曲列表是 Android_Music_Demo_json_h_array.xml 文件，虽然文件后缀名是 .xml，但内部其实是 JSON 格式，因为 cnblog 不让上传 .json 格式的文件，该文件里的缩略图都较大，是 .jpg 格式，而与之对应的 Android_Music_Demo_json_array.xml 文件里的缩略图，都很小，都是才不到10k的 .png 格式。
图 1
假设给定一个图片链接地址，想获得图片缩略图，核心代码如下所示，点击此处下载：
private Bitmap getBitmap(String url) {File f = fileCache.getFile(url);
// from SD cacheBitmap b = decodeFile(f);
if (b != null)
return b; // from web try { Bitmap bitmap = null; URL imageUrl = new URL(url);HttpURLConnection conn = (HttpURLConnection) imageUrl
.openConnection();
conn.setRequestMethod("GET"); // Sets the flag indicating whether this URLConnection allows input. // conn.setDoInput(true);conn.setConnectTimeout(3000);
conn.setReadTimeout(3000);
// Flag to define whether the protocol will automatically follow // redirects or not. conn.setInstanceFollowRedirects(true); int response_code = conn.getResponseCode(); if (response_code == 200) { InputStream is = conn.getInputStream(); OutputStream os = new FileOutputStream(f); StreamUtils.CopyStream(is, os);os.close();
conn.disconnect();
bitmap = decodeFile(f);
return bitmap; } else {conn.disconnect();
return null;
}
} catch (Throwable ex) {ex.printStackTrace();
if (ex instanceof OutOfMemoryError)memoryCache.clear();
return null;
}
}
private Bitmap decodeFile(File f) { try { // decode image size BitmapFactory.Options o = new BitmapFactory.Options(); o.inJustDecodeBounds = true; FileInputStream stream1 = new FileInputStream(f); BitmapFactory.decodeStream(stream1, null, o);stream1.close();
// Find the correct scale value. It should be the power of 2. final int REQUIRED_SIZE = 70; int width_tmp = o.outWidth, height_tmp = o.outHeight; int scale = 1;while (true) {
if (width_tmp / 2 < REQUIRED_SIZE|| height_tmp / 2 < REQUIRED_SIZE)
break;width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// decode with inSampleSize BitmapFactory.Options o2 = new BitmapFactory.Options();o2.inSampleSize = scale;
FileInputStream stream2 = new FileInputStream(f); Bitmap bitmap = BitmapFactory.decodeStream(stream2, null, o2);stream2.close();
return bitmap; } catch (FileNotFoundException e) { } catch (IOException e) {e.printStackTrace();
}
return null;
}
Android 获得图片并解码成缩略图以减少内存消耗,布布扣,bubuko.com
标签：android des style blog http color
原文地址：http://www.cnblogs.com/liuning8023/p/3835846.html
