显示图像从SD卡，但花时间在Android

Question

嗨在下面我显示sdcard.sdcard图像意味着存储到本地。但虽然privew图像后显示图像显示一些黑色。

想要显示平滑的预览与黑色screen.i无法找出问题。任何人都可以帮助我。

的Java

public class ImageGallery extends Activity { 

    Bundle bundle; 
    String catid, temp, responseJson; 
    JSONObject json; 
    ImageView imageViewPager; 
    // for parsing 
    JSONObject o1, o2; 
    JSONArray a1, a2; 
    int k; 
    Boolean toggleTopBar; 
    ArrayList<String> imageThumbnails; 
    ArrayList<String> imageFull; 
    public static int imagePosition=0; 
    SubsamplingScaleImageView imageView, imageViewPreview, fullImage ; 
    ImageView thumb1, back; 
    private LinearLayout thumb2; 
    RelativeLayout topLayout, stripeView; 
    RelativeLayout thumbnailButtons; 
    FrameLayout gridFrame; 

    //SharedPreferences data 
    SharedPreferences s1; 
    SharedPreferences.Editor editor; 

    int swipeCounter; 
    ParsingForFinalImages parsingObject; 
int position_grid; 
    SharedPreferences p; 

    Bitmap bm; 
    int numOfImagesInsidee; 
    LinearLayout backLinLayout; 
    public static boolean isThumb2=false; 
    public static boolean isThumb1=false; 

public static ViewPager viewPager; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_image_gallery); 
     //isThumb2=false; 
     toggleTopBar = false; 
     //position_grid=getIntent().getExtras().getInt("position"); 


     thumbnailButtons = (RelativeLayout)findViewById(R.id.thumbnailButtons); 
     topLayout = (RelativeLayout)findViewById(R.id.topLayout); 
     //fullImage = (SubsamplingScaleImageView)findViewById(R.id.fullimage); 

     backLinLayout = (LinearLayout)findViewById(R.id.lin_back); 
     backLinLayout.setOnClickListener(
       new View.OnClickListener() { 
        @Override 
        public void onClick(View view) { 

         Intent io = new Intent(getBaseContext(), MainActivity.class); 
         // clear the previous activity and start a new task 
         // System.gc(); 
         // io.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK); 
         startActivity(io); 
         finish(); 

        } 

       }); 

     ConnectionDetector cd = new ConnectionDetector(getBaseContext()); 
     Boolean isInternetPresent = cd.isConnectingToInternet(); 



     thumb1 = (ImageView)findViewById(R.id.thumb1); 
     thumb2 = (LinearLayout)findViewById(R.id.thumb2); 
     stripeView = (RelativeLayout)findViewById(R.id.stripeView) ; 
     gridFrame = (FrameLayout)findViewById(R.id.gridFrame); 


     thumb1.setOnClickListener(
       new View.OnClickListener() { 
        @Override 
        public void onClick(View view) { 

         stripeView.setVisibility(View.GONE); 
         gridFrame.setVisibility(View.VISIBLE); 
         viewPager.setVisibility(View.GONE); 
         //fullImage.setVisibility(View.GONE); 
         thumb1.setClickable(false); 
         isThumb1=true; 
isThumb2=false; 
         Log.i("Thumb Position 1",""+ImageGallery.imagePosition); 
         viewPager.removeAllViews(); 
         Fragment newFragment = new GridFragment2(); 
         FragmentTransaction ft = getFragmentManager().beginTransaction(); 
         ft.replace(R.id.gridFrame, newFragment).commit(); 


        } 

       }); 
     thumb2.setOnClickListener(
       new View.OnClickListener() { 
        @Override 
        public void onClick(View view) { 


         // stripeView.setVisibility(View.VISIBLE); 
         stripeView.setVisibility(View.GONE); 
         gridFrame.setVisibility(View.VISIBLE); 
         viewPager.setVisibility(View.GONE); 
         // fullImage.setVisibility(View.GONE); 
         thumb1.setClickable(true); 
         isThumb2=true; 
         isThumb1=false; 
         Log.i("Thumb Position 2",""+ImageGallery.imagePosition); 
         viewPager.removeAllViews(); 
         Fragment newFragment = new ImageStripeFragment(); 
         FragmentTransaction ft = getFragmentManager().beginTransaction(); 
         ft.replace(R.id.gridFrame, newFragment).commit(); 

        } 
       }); 




     // allow networking on main thread 
     StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
     StrictMode.setThreadPolicy(policy); 

     /*bundle = getIntent().getExtras(); 
     catid = bundle.getString("catid");*/ 
     // Toast.makeText(getBaseContext(), catid, Toast.LENGTH_LONG).show(); 


     // making json using the catalogue id we got 

     p = getSharedPreferences("gridData", Context.MODE_APPEND); 
     catid = p.getString("SelectedCatalogueIdFromGrid1", ""); 
     int clickedListPos = p.getInt("clickedPosition", 0); 



     imageViewPreview = (SubsamplingScaleImageView)findViewById(R.id.preview); 
     imageThumbnails = new ArrayList<String>(); 
     imageFull = new ArrayList<String>(); 
     s1 = this.getSharedPreferences("data", Context.MODE_APPEND); 
     editor = s1.edit(); 


     Log.d("catidfnl", catid); 
     numOfImagesInsidee = p.getInt("numberOfItemsSelectedFromGrid1", 0); 

     Log.d("blingbling2", String.valueOf(numOfImagesInsidee)); 

     // adding downloaded images to arraylist 
     for(int m=0;m<numOfImagesInsidee;m++){ 
      imageThumbnails.add(Environment.getExternalStorageDirectory()+"/"+"thumbImage" + catid + m+".png"); 
      imageFull.add(Environment.getExternalStorageDirectory()+"/"+"fullImage" + catid + m+".png"); 


      // imageFull.add("file://" + Environment.getExternalStorageDirectory() + "/" + "fullImage32.png"); 

     } 

     viewPager = (ViewPager) findViewById(R.id.pager); 
     ImagePagerAdapter adapter = new ImagePagerAdapter(); 
     viewPager.setAdapter(adapter); 


     // SubsamplingScaleImageView fullImage = new SubsamplingScaleImageView(ImageGallery.this); 













     // code to display image in a horizontal strip starts here 
     LinearLayout layout = (LinearLayout) findViewById(R.id.linear); 
     for (int i = 0; i < imageThumbnails.size(); i++) { 
      imageView = new SubsamplingScaleImageView(this); 
      imageView.setId(i); 

      imageView.setPadding(2, 2, 2, 2); 

      // Picasso.with(this).load("file://"+imageThumbnails.get(i)).into(imageView); 

      // imageView.setScaleType(ImageView.ScaleType.FIT_XY); 
      layout.addView(imageView); 

      ViewGroup.LayoutParams params = imageView.getLayoutParams(); 
      params.width = 200; 
      params.height = 200; 
      imageView.setLayoutParams(params); 

      imageView.setZoomEnabled(false); 
      imageView.setDoubleTapZoomScale(0); 

      imageView.setImage(ImageSource.uri(imageThumbnails.get(0))); 

      imageView.setOnClickListener(
        new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 



          imageView.setZoomEnabled(false); 
          imageViewPreview.setImage(ImageSource.uri(imageFull.get(view.getId()))); 
          imageView.recycle(); 
          imageViewPreview.recycle(); 

         } 
        }); 
     } 
     // code to display image in a horizontal strip ends here 

     imageViewPreview.setZoomEnabled(false); 

     /*imageViewPreview.setOnClickListener(
       new View.OnClickListener() { 
        @Override 
        public void onClick(View view) { 

         imageViewPreview.setZoomEnabled(false); 
         stripeView.setVisibility(View.GONE); 
         gridFrame.setVisibility(View.GONE); 
         viewPager.setVisibility(View.VISIBLE); 

        } 
       });*/ 

     imageViewPreview.setOnClickListener(new DoubleClickListener() { 

      @Override 
      public void onSingleClick(View v) { 
       Log.d("yo click", "single"); 
      } 

      @Override 
      public void onDoubleClick(View v) { 
       Log.d("yo click", "double"); 
      } 
     }); 


    } 


    public abstract class DoubleClickListener implements View.OnClickListener { 

     private static final long DOUBLE_CLICK_TIME_DELTA = 300;//milliseconds 

     long lastClickTime = 0; 

     @Override 
     public void onClick(View v) { 
      long clickTime = System.currentTimeMillis(); 
      if (clickTime - lastClickTime < DOUBLE_CLICK_TIME_DELTA){ 
       onDoubleClick(v); 
      } else { 
       onSingleClick(v); 
      } 
      lastClickTime = clickTime; 
     } 

     public abstract void onSingleClick(View v); 
     public abstract void onDoubleClick(View v); 
    } 




// @Override 
// public void onBackPressed() { 
//  Intent io = new Intent(getBaseContext(), MainActivity.class); 
//  // clear the previous activity and start a new task 
//  super.onBackPressed(); 
//  finish(); 
//  // System.gc(); 
//  // io.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK); 
//  startActivity(io); 
// } 



    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.menu_image_gallery, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

    private class ImagePagerAdapter extends PagerAdapter { 
     /* private int[] mImages = new int[] { 
       R.drawable.scroll3, 
       R.drawable.scroll1, 
       R.drawable.scroll2, 
       R.drawable.scroll4 

     };*/ 
     /* private String[] description=new String[] 
       { 
        "One","two","three","four" 
       }; 
*/ 
     @Override 
     public int getCount() { 
      Log.i("Image List Size", "" + imageFull.size()); 
      return imageFull.size(); 
     } 

     @Override 
     public boolean isViewFromObject(View view, Object object) { 
      return view == ((SubsamplingScaleImageView) object); 
     } 




     @Override 
     public Object instantiateItem(ViewGroup container, int position) { 
      Context context = ImageGallery.this; 

      SubsamplingScaleImageView fullImage = new SubsamplingScaleImageView(ImageGallery.this); 

      // for placeholder 
      // fullImage.setImage(ImageSource.resource(R.drawable.tan2x)); 

      if(!GridFragment2.isSelectedGrid2&&!ImageStripeFragment.isImageStripe) { 
      imagePosition = position; 
      fullImage.setImage(ImageSource.uri(imageFull.get(imagePosition))); 

     } 
     /* else if(!ImageStripeFragment.isImageStripe) 
     { 
      imagePosition = position; 
      fullImage.setImage(ImageSource.uri(imageFull.get(imagePosition))); 
     } 
     else if(ImageStripeFragment.isImageStripe) 
     { 
      position=imagePosition; 
      viewPager.setCurrentItem(imagePosition); 
      fullImage.setImage(ImageSource.uri(imageFull.get(position))); 
     }*/ 
      else 
     { 
      position=imagePosition; 
      viewPager.setCurrentItem(imagePosition); 
      fullImage.setImage(ImageSource.uri(imageFull.get(position))); 


      //viewPager.removeAllViews(); 

     } 

      // ImageView imageViewPager = new ImageView(context); 
      // ImageView imageViewPager = new ImageView(getApplicationContext()); 
      // SubsamplingScaleImageView fullImage = new SubsamplingScaleImageView(ImageGallery.this); 

      GridFragment2.isSelectedGrid2=false; 
      ImageStripeFragment.isImageStripe=false; 

      // Log.i("Image Resource", "" + ImageSource.uri(imageFull.get(position))); 
     // imageViewPager.setImageBitmap(BitmapFactory.decodeFile(imageFull.get(position))); 
     // imageViewPager.setImageBitmap(myBitmap); 

      // fullImage.setImage(ImageSource.bitmap(bmImg)); 

      //imageView.setImageResource(Integer.parseInt(imageFull.get(position))); 
      /*int padding = context.getResources().getDimensionPixelSize(
       R.dimen.padding_medium); 
      imageView.setPadding(padding, padding, padding, padding);*/ 
      /*imageView.setScaleType(ImageView.ScaleType.CENTER); 
      imageView.setImageResource(Integer.parseInt(imageFull.get(position))); 

      if(position==3) 
      { 

      }*/ 
      // Log.i("Image Position",""+position); 
      /*text.setText(description[position]); 
      Log.i("Text Position",""+position);*/ 
      /*switch(position) 
      { 

      case 0: 
       String pos=String.valueOf(position); 
      text.setText(pos); 

       break; 
      case 1: 
       String pos1=String.valueOf(position); 
       text.setText(pos1); 
       break; 
      case 2: 
       String pos2=String.valueOf(position); 
       text.setText(pos2); 
       break; 
      case 3: 
       String pos3=String.valueOf(position); 
       text.setText(pos3); 
       break; 
      }*/ 



      fullImage.setOnClickListener(
        new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 

          if (toggleTopBar == false) { 
           // thumbnailButtons.setVisibility(View.GONE); 
           thumbnailButtons.animate() 
             .translationY(-2000) 
             .setDuration(1000) 
             .start(); 
           toggleTopBar = true; 
          } else if (toggleTopBar == true) { 
           // thumbnailButtons.setVisibility(View.VISIBLE); 
           thumbnailButtons.animate() 
             .translationY(0) 
             .setDuration(1000) 
             .start(); 
           toggleTopBar = false; 
          } 

         } 
        }); 
      ((ViewPager) container).addView(fullImage, 0); 

      return fullImage; 
     } 

     @Override 
     public void destroyItem(ViewGroup container, int position, Object object) { 
      ((ViewPager) container).removeView((SubsamplingScaleImageView) object); 
     } 
     /* @Override 
     public void destroyItem(View collection, int position, Object o) { 
      Log.d("DESTROY", "destroying view at position " + position); 
      View view = (View) o; 
      ((ViewPager) collection).removeView(view); 
      view = null; 
     }*/ 


    } 

    @Override 
    public void onBackPressed() { 
     // TODO Auto-generated method stub 

     super.onBackPressed(); 

     Intent intent = new Intent(getApplicationContext(), MainActivity.class); 
     intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
     startActivity(intent); 
     finish(); 

    } 

Answer 1

使用本ImageLoader的类

public class ImageLoader { 
MemoryCache memoryCache = new MemoryCache(); 
FileCache fileCache; 
private Map<ImageView, String> imageViews = Collections 
     .synchronizedMap(new WeakHashMap<ImageView, String>()); 
ExecutorService executorService; 
Handler handler = new Handler();// handler to display images in UI thread 
int stub_id; 
int widht; 

public ImageLoader(Context context, int stub_idx) { 
    fileCache = new FileCache(context); 
    executorService = Executors.newFixedThreadPool(5); 

    stub_id = stub_idx; 
} 

public void DisplayImage(String url, ImageView imageView, int widht, ProgressBar bar) { 
    this.widht = widht; 

    imageViews.put(imageView, url); 
    Bitmap bitmap = memoryCache.get(url); 
    if (bitmap != null) 
    { 
     bar.setVisibility(View.GONE); 
     imageView.setImageBitmap(bitmap); 
    } 
    else { 
     queuePhoto(url, imageView, widht, bar); 
     imageView.setImageResource(stub_id); 
    } 
} 

private void queuePhoto(String url, ImageView imageView, int w, ProgressBar bar) { 
    PhotoToLoad p = new PhotoToLoad(url, imageView, bar); 
    executorService.submit(new PhotosLoader(p, w)); 
} 

public Bitmap getBitmap(String url, int w) { 
    File f = fileCache.getFile(url); 

    // from SD cache 
    Bitmap b = decodeFile(f, w); 
    if (b != null) 
     return b; 

    // from web 
    try { 
     Bitmap bitmap = null; 
     URL imageUrl = new URL(url); 
     HttpURLConnection conn = (HttpURLConnection) imageUrl 
       .openConnection(); 
     conn.setConnectTimeout(30000); 
     conn.setReadTimeout(30000); 
     conn.setInstanceFollowRedirects(true); 
     InputStream is = conn.getInputStream(); 
     OutputStream os = new FileOutputStream(f); 
     Utils.CopyStream(is, os); 
     os.close(); 
     conn.disconnect(); 
     bitmap = decodeFile(f, w); 
     return bitmap; 
    } catch (Throwable ex) { 
     ex.printStackTrace(); 
     if (ex instanceof OutOfMemoryError) 
      memoryCache.clear(); 
     return null; 
    } 
} 

// decodes image and scales it to reduce memory consumption 
private Bitmap decodeFile(File f, int w) { 
    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 = w; 
     System.out.println("screen wdth " + widht); 
     int width_tmp = o.outWidth, height_tmp = o.outHeight; 
     System.out.println("image with === " + width_tmp); 
     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) { 
     Log.e(e.getMessage(), ""); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
    return null; 
} 

// Task for the queue 
private class PhotoToLoad { 
    public String url; 
    public ImageView imageView; 
    public ProgressBar bar; 

    public PhotoToLoad(String u, ImageView i, ProgressBar progressBar) { 
     url = u; 
     imageView = i; 
     bar = progressBar; 
    } 
} 

class PhotosLoader implements Runnable { 
    PhotoToLoad photoToLoad; 
    int w; 

    PhotosLoader(PhotoToLoad photoToLoad, int w) { 
     this.photoToLoad = photoToLoad; 
     this.w = w; 

    } 

    @Override 
    public void run() { 
     try { 
      if (imageViewReused(photoToLoad)) 
       return; 
      Bitmap bmp = getBitmap(photoToLoad.url, w); 
      memoryCache.put(photoToLoad.url, bmp); 
      if (imageViewReused(photoToLoad)) 
       return; 
      BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad); 
      handler.post(bd); 
     } catch (Throwable th) { 
      th.printStackTrace(); 
     } 
    } 
} 

boolean imageViewReused(PhotoToLoad photoToLoad) { 
    String tag = imageViews.get(photoToLoad.imageView); 
    return tag == null || !tag.equals(photoToLoad.url); 
} 

// Used to display bitmap in the UI thread 
class BitmapDisplayer implements Runnable { 
    Bitmap bitmap; 
    PhotoToLoad photoToLoad; 

    public BitmapDisplayer(Bitmap b, PhotoToLoad p) { 
     bitmap = b; 
     photoToLoad = p; 
    } 

    public void run() { 
     if (imageViewReused(photoToLoad)) 
      return; 
     if (bitmap != null) 
      photoToLoad.imageView.setImageBitmap(bitmap); 
     else 
      photoToLoad.imageView.setImageResource(stub_id); 

     photoToLoad.bar.setVisibility(View.GONE); 
    } 
} 

public void clearCache() { 
    memoryCache.clear(); 
    fileCache.clear(); 
} 

然后做出新的类文件缓存

public class FileCache { 

private File cacheDir; 

public FileCache(Context context) { 
    // Find the dir to save cached images 
    if (android.os.Environment.getExternalStorageState().equals(
      android.os.Environment.MEDIA_MOUNTED)) 
     cacheDir = new File(
       android.os.Environment.getExternalStorageDirectory(), 
       "LazyList"); 
    else 
     //cacheDir = url.getCacheDir(); 
    if (!cacheDir.exists()) 
     cacheDir.mkdirs(); 
} 

public File getFile(String url) { 
    // I identify images by hashcode. Not a perfect solution, good for the 
    // demo. 
    String filename = String.valueOf(url.hashCode()); 
    // Another possible solution (thanks to grantland) 
    // String filename = URLEncoder.encode(url); 
    File f = new File(cacheDir, filename); 
    return f; 

} 

public void clear() { 
    File[] files = cacheDir.listFiles(); 
    if (files == null) 
     return; 
    for (File f : files) 
     f.delete(); 
} 

} 

然后最后让内存缓存类，所有三个seperatly类

public class MemoryCache { 

private static final String TAG = "MemoryCache"; 
private Map<String, Bitmap> cache=Collections.synchronizedMap(
     new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering 
private long size=0;//current allocated size 
private long limit=1000000;//max memory in bytes 

public MemoryCache(){ 
    //use 25% of available heap size 
    setLimit(Runtime.getRuntime().maxMemory()/4); 
} 

public void setLimit(long new_limit){ 
    limit=new_limit; 
    Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB"); 
} 

public Bitmap get(String id){ 
    try{ 
     if(!cache.containsKey(id)) 
      return null; 
     //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 
     return cache.get(id); 
    }catch(NullPointerException ex){ 
     ex.printStackTrace(); 
     return null; 
    } 
} 

public void put(String id, Bitmap bitmap){ 
    try{ 
     if(cache.containsKey(id)) 
      size-=getSizeInBytes(cache.get(id)); 
     cache.put(id, bitmap); 
     size+=getSizeInBytes(bitmap); 
     checkSize(); 
    }catch(Throwable th){ 
     th.printStackTrace(); 
    } 
} 

private void checkSize() { 
    Log.i(TAG, "cache size="+size+" length="+cache.size()); 
    if(size>limit){ 
     Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();//least recently accessed item will be the first one iterated 
     while(iter.hasNext()){ 
      Entry<String, Bitmap> entry=iter.next(); 
      size-=getSizeInBytes(entry.getValue()); 
      iter.remove(); 
      if(size<=limit) 
       break; 
     } 
     Log.i(TAG, "Clean cache. New size "+cache.size()); 
    } 
} 

public void clear() { 
    try{ 
     //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 
     cache.clear(); 
     size=0; 
    }catch(NullPointerException ex){ 
     ex.printStackTrace(); 
    } 
} 

long getSizeInBytes(Bitmap bitmap) { 
    if(bitmap==null) 
     return 0; 
    return bitmap.getRowBytes() * bitmap.getHeight(); 
}