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Android-异步加载图片
刚刚复习了之前学的异步加载图片,于是决定写下来,增强记忆
想要加载图片,必须获得所有图片的URL地址。这里图片的URL地址存在了List数组。
异步加载图片有两种方式(我这里使用两种方式):1.自己开线程来加载图片,然后使用Handler来更新UI;2.使用AsyncTask来加载图片。
1.使用子线程来加载图片。
1 private Handler handler = new Handler() 2 { 3 @Override 4 public void handleMessage(Message msg) { 5 if(mImageView.getTag().equals(mUrlString)) 6 { 7 mImageView.setImageBitmap(mBitmap); 8 } 9 } 10 }; 11 public void loadImageByThread(ImageView imageView, final String urlString) { 12 mImageView = imageView; 13 mUrlString = urlString; 14 new Thread() { 15 @Override 16 public void run() { 17 mBitmap = getBitmap(mUrlString); 18 Message message = Message.obtain(); 19 message.obj = urlString; 20 handler.sendMessage(message); 21 } 22 }.start(); 23 }
1 private Bitmap getBitmap(String urlString) 2 { 3 Bitmap bitmap = null; 4 5 URL url = null; 6 HttpURLConnection httpURLConnection = null; 7 InputStream is = null; 8 try { 9 url = new URL(urlString); 10 httpURLConnection = (HttpURLConnection) url.openConnection(); 11 is = httpURLConnection.getInputStream(); 12 bitmap = BitmapFactory.decodeStream(is); 13 } catch (MalformedURLException e) { 14 e.printStackTrace(); 15 } catch (IOException e) { 16 e.printStackTrace(); 17 } 18 finally { 19 try { 20 is.close(); 21 } catch (IOException e) { 22 e.printStackTrace(); 23 } 24 } 25 return bitmap; 26 }
2.使用AsyncTask来加载图片
1 private class MyAsyncTask extends AsyncTask<String, Void, Bitmap> 2 { 3 4 protected Bitmap doInBackground(String... params) { 5 return getBitmap(params[0]); 6 } 7 8 @Override 9 protected void onPostExecute(Bitmap bitmap) { 10 11 if(mImageView != null && bitmap != null && mUrlString.equals(mImageView.getTag())) 12 { 13 mImageView.setImageBitmap(bitmap); 14 Utils.addBitmapToLruCache(bitmap, mUrlString); 15 } 16 } 17 }
3.使用内存来缓存图片
1 private static long mMaxMemory = Runtime.getRuntime().maxMemory(); 2 private static long mApplyMemory = mMaxMemory / 10; 3 private static LruCache<String, Bitmap> mLruCache = new LruCache<String, Bitmap>((int)mApplyMemory) 4 { 5 @Override 6 protected int sizeOf(String key, Bitmap value) { 7 return value.getByteCount(); 8 } 9 }; 10 public static boolean isBitmapExistsInLruCache(String urlString) 11 { 12 return mLruCache.get(urlString) != null; 13 } 14 public static void addBitmapToLruCache(Bitmap bitmap, String urlString) 15 { 16 //Log.i("main", "图片大小 = " + bitmap.getByteCount() * 1.0f/ 1024 / 1024); 17 mLruCache.put(urlString, bitmap); 18 } 19 public static Bitmap getBitmaoLruCache(String urlString) 20 { 21 return mLruCache.get(urlString); 22 }
Android-异步加载图片
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