详解Android_性能优化之ViewPager加载成百上千高清大图oom解决方案

List<SubsamplingScaleImageView> mViews = new ArrayList<>(); 
     
    int size = mDatas.size(); 
    for (int i = 0; i < size; i++) { 
      SubsamplingScaleImageView view = new SubsamplingScaleImageView(this); 
      mViews.add(view); 
    } 
 
    mBinding.viewpager.setAdapter(new MyAdapter()); 

class MyAdapter extends PagerAdapter { 
 
    @Override 
    public int getCount() { 
      return mDatas.size(); 
    } 
 
    @Override 
    public boolean isViewFromObject(View view, Object object) { 
      return view == object; 
    } 
 
    @Override 
    public Object instantiateItem(ViewGroup container, final int position) { 
 
      ViewGroup.LayoutParams params = new ViewGroup.LayoutParams( 
          ViewPager.LayoutParams.MATCH_PARENT,ViewPager.LayoutParams.MATCH_PARENT); 
      final SubsamplingScaleImageView imageView = mViews.get(position); 
      imageView.setLayoutParams(params); 
 
      final String url = mDatas.get(position); 
      String cacheExists = cacheExists(url); 
      if(TextUtils.isEmpty(cacheExists)) {//没缓存 需要压缩(压缩耗时 异步) 
        new AsyncTask<Void, Void, String>() { 
          @Override 
          protected String doInBackground(Void... voids) { 
            String cacheNoExistsPath = getCacheNoExistsPath(url); 
            BitmapCompressUtils.compressBitmap(url, cacheNoExistsPath); 
            File file = new File(cacheNoExistsPath); 
            if (file.exists()) {//存在表示成功 
              return cacheNoExistsPath; 
            } else { 
              return url; 
            } 
          } 
 
          @Override 
          protected void onPostExecute(String s) { 
            imageView.setImage(ImageSource.uri(s)); 
          } 
 
        }.execute(); 
 
 
      } else {//有缓存 直接显示 
        imageView.setImage(ImageSource.uri(cacheExists)); 
      } 
 
      container.addView(imageView); 
      return imageView; 
 
    } 
 
    @Override 
    public void destroyItem(ViewGroup container, int position, Object object) { 
 
      SubsamplingScaleImageView imageView = mViews.get(position); 
      if(imageView != null) { 
        imageView.recycle(); 
      } 
 
      container.removeView(imageView); 
 
    } 
  } 

/** 
   * 判断当前图片url对应的压缩过的缓存是否存在 ""表示不存在 
   * 
   * @param url 图片路径 
   * @return 
   */ 
  private String cacheExists(String url) { 
    try { 
      File fileDir = new File(mCacheRootPath); 
      if(!fileDir.exists()) { 
        fileDir.mkdirs(); 
      } 
 
      File file = new File(mCacheRootPath,new StringBuffer().append(MD5EncryptorUtils.md5Encryption(url)).toString()); 
      if(file.exists()) { 
        return file.getAbsolutePath(); 
      } 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
 
    return ""; 
  } 
 
  public String getCacheNoExistsPath(String url) { 
    File fileDir = new File(mCacheRootPath); 
    if(!fileDir.exists()) { 
      fileDir.mkdirs(); 
    } 
 
 
    return new StringBuffer().append(mCacheRootPath) 
        .append(MD5EncryptorUtils.md5Encryption(url)).toString(); 
  } 

for (int i = 0; i < 4; i++) { 
      SubsamplingScaleImageView view = new SubsamplingScaleImageView(this); 
      mViews.add(view); 
    } 
 
    mBinding.viewpager.setAdapter(new MyAdapter()); 

class MyAdapter extends PagerAdapter { 
 
    @Override 
    public int getCount() { 
      return mDatas.size(); 
    } 
 
    @Override 
    public boolean isViewFromObject(View view, Object object) { 
      return view == object; 
    } 
 
    @Override 
    public Object instantiateItem(ViewGroup container, final int position) { 
 
      ViewGroup.LayoutParams params = new ViewGroup.LayoutParams( 
          ViewPager.LayoutParams.MATCH_PARENT,ViewPager.LayoutParams.MATCH_PARENT); 
 
      int i = position % 4; 
      final SubsamplingScaleImageView imageView = mViews.get(i); 
      imageView.setLayoutParams(params); 
 
      final String url = mDatas.get(position); 
      String cacheExists = cacheExists(url); 
      if(TextUtils.isEmpty(cacheExists)) {//没缓存 需要压缩(压缩耗时 异步) 
        new AsyncTask<Void, Void, String>() { 
          @Override 
          protected String doInBackground(Void... voids) { 
            String cacheNoExistsPath = getCacheNoExistsPath(url); 
            BitmapCompressUtils.compressBitmap(url, cacheNoExistsPath); 
            File file = new File(cacheNoExistsPath); 
            if (file.exists()) {//存在表示成功 
              return cacheNoExistsPath; 
            } else { 
              return url; 
            } 
          } 
 
          @Override 
          protected void onPostExecute(String s) { 
            imageView.setImage(ImageSource.uri(s)); 
          } 
 
        }.execute(); 
 
 
      } else {//有缓存 直接显示 
        imageView.setImage(ImageSource.uri(cacheExists)); 
      } 
 
      container.addView(imageView); 
      return imageView; 
 
    } 
 
    @Override 
    public void destroyItem(ViewGroup container, int position, Object object) { 
      int i = position % 4; 
      SubsamplingScaleImageView imageView = mViews.get(i); 
      if(imageView != null) { 
        imageView.recycle(); 
      } 
 
      container.removeView(imageView); 
 
    }