使用Lrucache，图片滑动时使用默认图片，停止时加载

Posted 2020-08-12 杨伟乔

注意：LruCache是有版本限制的，低版本的sdk需要在libs文件夹添加相应的support-4v文件。
本文改造的大部分是参考http://www.iteye.com/topic/1118828，感谢。
不废话直接上工程代码，内有关键注释，项目就不上传了，自己对照着上面网址改呗。

首先是Application文件，负责创建图片存储文件夹：

public class MyApp extends Application{

    @Override

    public void onCreate() {

        super.onCreate();

        File f = new File(Environment.getExternalStorageDirectory()+"/TestSyncListView/pic/");

        if (!f.exists()) {

            f.mkdirs();

        }

    }

}

图像读取工具类：

public class SyncImageLoaderUtil {     private Object lock = new Object();              private boolean mAllowLoad = true;          private boolean firstLoad = true;          private int mStartLoadLimit = 0;          private int mStopLoadLimit = 0;          final Handler handler = new Handler();      //    private HashMap<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>();          private LruCache<String,Bitmap> mMemoryCache;           RunInOtherThread runInOutherThread;          public SyncImageLoaderUtil(Context context) {          super();                    int memClass = ((ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();         int cacheSize = 1024 * 1024 *memClass / 8;         mMemoryCache = new LruCache<String, Bitmap>(cacheSize){             @Override             protected int sizeOf(String key, Bitmap value) {                 // TODO Auto-generated method stub                 return value.getRowBytes();             }         };                   runInOutherThread = new RunInOtherThread();          runInOutherThread.start();      }          public interface OnImageLoadListener {          public void onImageLoad(Integer t, Drawable drawable);              public void onError(Integer t);      }          public void setLoadLimit(int startLoadLimit, int stopLoadLimit) {          if (startLoadLimit > stopLoadLimit) {  //          LogUtil.i("test", startLoadLimit+"--错误---"+stopLoadLimit);             return;          }          mStartLoadLimit = startLoadLimit;          mStopLoadLimit = stopLoadLimit;      }          public void restore() {          mAllowLoad = true;          firstLoad = true;      }          public void lock() {          mAllowLoad = false;          firstLoad = false;      }          public void unlock() {          mAllowLoad = true;          synchronized (lock) {              lock.notifyAll();          }      }          public void loadImage(Integer t, String imageUrl,              OnImageLoadListener listener) {          final OnImageLoadListener mListener = listener;          final String mImageUrl = imageUrl;          final Integer mt = t;                      runInOutherThread.getHandler().post(new Runnable() {                  @Override              public void run() {                  if (!mAllowLoad) {                      synchronized (lock) {                          try {                              lock.wait();                          } catch (InterruptedException e) {                              // TODO Auto-generated catch block                              e.printStackTrace();                          }                      }                  }                                      if (mAllowLoad && firstLoad) {                      loadImage(mImageUrl, mt, mListener);                  }      //                LogUtil.e("test", "原始开始："+mStartLoadLimit+"原始当前位置："+mt+"原始结束："+mStopLoadLimit);                 if (mAllowLoad && mt <= mStopLoadLimit && mt >= mStartLoadLimit) {  //                  LogUtil.e("test", "开始："+mStartLoadLimit+"当前位置："+mt+"结束："+mStopLoadLimit);                     loadImage(mImageUrl, mt, mListener);                 }              }              });      }              private void loadImage(final String mImageUrl, final Integer mt,              final OnImageLoadListener mListener) {              if (mImageUrl!=null && mMemoryCache.get(mImageUrl)!=null) {  //            SoftReference<Drawable> softReference = imageCache.get(mImageUrl);              final Drawable d = new BitmapDrawable(mMemoryCache.get(mImageUrl));  //            LogUtil.d("ppp", "drawable:"+d);             if (d != null) {                  handler.post(new Runnable() {                      @Override                      public void run() {                          if (mAllowLoad) {                              mListener.onImageLoad(mt, d);                          }                      }                  });                  return;              }          }          try {              final Drawable d = loadImageFromUrl(mImageUrl);              if (d != null) {                  mMemoryCache.put(mImageUrl, ((BitmapDrawable)d).getBitmap());             }              handler.post(new Runnable() {                  @Override                  public void run() {                      if (mAllowLoad) {                          mListener.onImageLoad(mt, d);                      }                  }              });          } catch (IOException e) {              handler.post(new Runnable() {                  @Override                  public void run() {                      mListener.onError(mt);                  }              });              e.printStackTrace();          }      }          public static Drawable loadImageFromUrl(String url) throws IOException {          //DebugUtil.debug(url);          if (Environment.getExternalStorageState().equals(                  Environment.MEDIA_MOUNTED)) {              File f = new File(Environment.getExternalStorageDirectory()                      + "/Weiyu/pic/" + MD5Util.getMD5(url.getBytes()));              if (f.exists()) {                  FileInputStream fis = new FileInputStream(f);                  Drawable d = Drawable.createFromStream(fis, "src");                  return d;              }              URL m = new URL(url);              InputStream i = (InputStream) m.getContent();              DataInputStream in = new DataInputStream(i);              FileOutputStream out = new FileOutputStream(f);              byte[] buffer = new byte[1024];              int byteread = 0;              while ((byteread = in.read(buffer)) != -1) {                  out.write(buffer, 0, byteread);              }                           in.close();              out.close();             return loadImageFromUrl(url);          } else {              URL m = new URL(url);              InputStream i = (InputStream) m.getContent();              Drawable d = Drawable.createFromStream(i, "src");              return d;          }          }  }

　　
线程辅助类：

public class RunInOtherThread {     private static final String LOG_TAG = "RunInOtherThread";            private LooperThread localThread = new LooperThread();              private boolean isRunning = true;          public Handler getHandler(){          return localThread.getHandler();      }              private class LooperThread extends Thread {          private Handler mHandler;              public void run() {              Looper.prepare();              mHandler = new Handler() {                  public void handleMessage(Message msg) {                      onReceiveMessage(msg.what);                  }              };              Looper.loop();          }                      Handler getHandler(){              return mHandler;          }             }              public void start(){          localThread.start();      }              public void quit(){          localThread.getHandler().getLooper().quit();      }              public void sendMessage(int what){          getHandler().sendEmptyMessage(what);      }              public Thread getThread(){          return localThread;      }              public void onReceiveMessage(int what){}; }

　　
使用类：

// 实例化工具类 SyncImageLoaderUtil syncImageLoader = new SyncImageLoaderUtil(mContext);   syncImageLoader.loadImage(position, model.mPic, imageLoadListener);//应用接口：参数一是加载图片的位置；参数二是加载的ImageView；参数三是回调接口   // map保存的键是位置，值是listview对应位置的布局 HashMap map = new HashMap(); map.put(position, convertView);   SyncImageLoaderUtil.OnImageLoadListener imageLoadListener = new SyncImageLoaderUtil.OnImageLoadListener() {           @Override         public void onImageLoad(Integer t, Drawable drawable) {             View view = (View) map.get(t);             if (view != null) {                 ImageView iv = (ImageView) view.findViewById(R.id.image);                 iv.setBackgroundDrawable(drawable);             }         }           @Override         public void onError(Integer t) {                         // 图片加载失败                        // 取得listview对应的位置的行的内容布局                     MusicModel model = (MusicModel) getItem(t);             View view = mListView.findViewWithTag(model);             if (view != null) {                 ImageView iv = (ImageView) view.findViewById(R.id.image);                 iv.setBackgroundResource(R.drawable.img_pic);             }         }       };     // 实现类而且需要实现OnScrollListener接口 public void loadImage() {                 // 不要在这里使用listview的getFirstVisiblePosition方法，位置不准         if (end >= getCount()) {             end = getCount() - 1;         }         syncImageLoader.setLoadLimit(start, end);         syncImageLoader.unlock();     }       @Override     public void onScrollStateChanged(AbsListView view, int scrollState) {         // TODO Auto-generated method stub         if (lodingView) {             switch (scrollState) {             case AbsListView.OnScrollListener.SCROLL_STATE_FLING:                 syncImageLoader.lock();                 break;             case AbsListView.OnScrollListener.SCROLL_STATE_IDLE:                   loadImage();                 br 以上是关于使用Lrucache，图片滑动时使用默认图片，停止时加载的主要内容，如果未能解决你的问题，请参考以下文章 LIstview滑动时不加载图片，停止时加载！ swiper中有视频时，滑动停止后视频停止播放 Android批量图片载入经典系列——使用LruCacheAsyncTask缓存并异步载入图片 综合使用LruCache和DiskLruCache 缓存图片 Fresco对Listview等快速滑动时停止加载 图片懒加载使用