圖像加載和緩存的Android

Question

我有一個適配器和一個的AsyncTask來ListFragment加載數據，目前它建立了文本列表視圖，我已經把非動態圖像佔位符現在。我在想，如果有人能闡明的最佳途徑光來實現從網上下載的圖片，我的URL從谷歌測試和高速緩存，並顯示通過適配器這些圖像，我沒有scrolllistener卻爲網頁時到達底部，但我還挺停留在什麼是最好的解決方案，在傳遞和加載我的動態畫面會是這樣，如果有人可以告訴我加載圖片，最好緩存它們的最好辦法，所以我不不必下載它們每次SD卡和一切。

這裏是我的班

TestListFragment

public class TestListFragment extends ListFragment 
     implements 
     android.support.v4.app.LoaderManager.LoaderCallbacks<List<TestItemModel>> { 

    TestCustomArrayAdapter _adapter; 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 

     System.out.println("TestListFragment.onActivityCreated"); 

     // Initially there is no data 
     setEmptyText("Refresh: No Data Here"); 

     // Create an empty adapter we will use to display the loaded data. 
     _adapter = new TestCustomArrayAdapter(getActivity()); 
     setListAdapter(_adapter); 

     // Start out with a progress indicator. 
     setListShown(false); 

     // Prepare the loader. Either re-connect with an existing one, 
     // or start a new one. 
     getLoaderManager().initLoader(0, null, this); 

    } 

    @Override 
    public void onListItemClick(ListView l, View v, int position, long id) { 
     // Insert desired behavior here. 
     Log.i("TestListFragment", "Item clicked: " + id); 
     TestItemModel ti = this._adapter.getItem(position); 
     System.out.println(ti.getId()); 

    } 

    @Override 
    public Loader<List<TestItemModel>> onCreateLoader(int arg0, Bundle arg1) { 
     System.out.println("TestListFragment.onCreateLoader"); 
     return new TestListLoaderAsync(getActivity()); 
    } 

    @Override 
    public void onLoadFinished(Loader<List<TestItemModel>> arg0, 
      List<TestItemModel> data) { 
     _adapter.setData(data); 
     System.out.println("TestListFragment.onLoadFinished"); 
     // The list should now be shown. 
     if (isResumed()) { 
      setListShown(true); 
     } else { 
      setListShownNoAnimation(true); 
     } 
    } 

    @Override 
    public void onLoaderReset(Loader<List<TestItemModel>> arg0) { 
     _adapter.setData(null); 
    } 

} 

TestCustomArrayAdapter

public class TestCustomArrayAdapter extends ArrayAdapter<TestItemModel> { 
    private final LayoutInflater _inflater; 
    public OnItemClickListener ol; 

    public TestCustomArrayAdapter(Context context) { 
     super(context, R.layout.test_list_fragment); 
     _inflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    } 

    public void setData(List<TestItemModel> data) { 
     clear(); 
     if (data != null) { 
      for (TestItemModel appEntry : data) { 
       add(appEntry); 
      } 
     } 
    } 

    /** 
    * Populate new items in the list. 
    */ 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     View view; 

     if (convertView == null) { 
      view = _inflater.inflate(R.layout.test_single_item, parent, false); 
     } else { 
      view = convertView; 
     } 

     TestItemModel item = getItem(position); 
     ((TextView) view.findViewById(R.id.item_label)).setText(item.getName()); 
     ((TextView) view.findViewById(R.id.item_id)).setText(item.getId()); 
     ImageView image = (ImageView) view.findViewById(R.id.image_id); 
     Resources resources = this.getContext().getResources(); 
     image.setImageDrawable(resources.getDrawable(R.drawable.ic_launcher)); 
     Button btn = (Button) view.findViewById(R.id.button_id); 
     Button btn2 = (Button) view.findViewById(R.id.button_id_2); 
     Button btn3 = (Button) view.findViewById(R.id.button_id_3); 
     ol = new OnItemClickListener(position, item); 
     btn.setOnClickListener(ol); 
     btn.setTag(1); 
     btn2.setOnClickListener(ol); 
     btn2.setTag(2); 
     btn3.setOnClickListener(ol); 
     btn3.setTag(3); 

     return view; 
    } 

    private class OnItemClickListener implements OnClickListener { 
     private int _position; 
     private TestItemModel _ti; 

     public OnItemClickListener(int position, TestItemModel ti) { 
      _position = position; 
      _ti = ti; 
     } 

     // TODO 
     // provide functionality for which button was clicked then pass the item 
     // to which it was clicked in. 
     @Override 
     public void onClick(View v) { 
      switch (v.getId()) { 
      case R.id.button_id: 
       // btn clicked 
       Toast.makeText(getContext(), 
         " Button1 clicked at positon" + v.getTag(), 
         Toast.LENGTH_SHORT).show(); 
       break; 
      case R.id.button_id_2: 
       // btn2 clicked 
       Toast.makeText(getContext(), 
         " Button2 clicked at positon" + v.getTag(), 
         Toast.LENGTH_SHORT).show(); 
       break; 
      case R.id.button_id_3: 
       Toast.makeText(getContext(), 
         " Button3 clicked at positon" + v.getTag(), 
         Toast.LENGTH_SHORT).show(); 
       // btn 3 clciked 
       break; 
      } 

      // the view is the button, so you get get the tag it has set with 
      // v.getTag() to know what button is pressed. 
      Log.v("YOOO", 
        "Button Click at position " + _position + " " + v.getTag() 
          + " Item ID = " + _ti.getId()); 

     } 
    } 

} 

TestListLoaderAsync

public class TestListLoaderAsync extends AsyncTaskLoader<List<TestItemModel>> { 

    List<TestItemModel> _models; 

    public TestListLoaderAsync(Context context) { 
     super(context); 
    } 

    @Override 
    public List<TestItemModel> loadInBackground() { 
     System.out.println("TestListLoader.loadInBackground"); 

     // You should perform the heavy task of getting data from 
     // Internet or database or other source 
     // Here, we are generating some Sample data 

     // Create corresponding array of entries and load with data. 
     List<TestItemModel> entries = new ArrayList<TestItemModel>(5); 
     entries.add(new TestItemModel("Java", "1")); 
     entries.add(new TestItemModel("C++", "2")); 
     entries.add(new TestItemModel("Python", "3")); 
     entries.add(new TestItemModel("JavaScript", "4")); 
     entries.add(new TestItemModel("D", "5")); 
     entries.add(new TestItemModel("C", "6")); 
     entries.add(new TestItemModel("Perl", "7")); 
     entries.add(new TestItemModel("Fortran", "8")); 
     entries.add(new TestItemModel("Cobalt", "9")); 
     entries.add(new TestItemModel("Ruby", "10")); 
     entries.add(new TestItemModel("Pascal", "11")); 
     entries.add(new TestItemModel("HTML", "12")); 
     entries.add(new TestItemModel("CSS", "13")); 
     entries.add(new TestItemModel("PHP", "14")); 
     entries.add(new TestItemModel("MYSQL", "15")); 
     TestItemModel lastItem = new TestItemModel("C#", "16"); 
     lastItem.setId("TestingId"); 
     entries.add(lastItem); 

     return entries; 
    } 

    /** 
    * Called when there is new data to deliver to the client. The super class 
    * will take care of delivering it; the implementation here just adds a 
    * little more logic. 
    */ 
    @Override 
    public void deliverResult(List<TestItemModel> listOfData) { 
     if (isReset()) { 
      // An async query came in while the loader is stopped. We 
      // don't need the result. 
      if (listOfData != null) { 
       onReleaseResources(listOfData); 
      } 
     } 
     List<TestItemModel> oldApps = listOfData; 
     _models = listOfData; 

     if (isStarted()) { 
      // If the Loader is currently started, we can immediately 
      // deliver its results. 
      super.deliverResult(listOfData); 
     } 

     // At this point we can release the resources associated with 
     // 'oldApps' if needed; now that the new result is delivered we 
     // know that it is no longer in use. 
     if (oldApps != null) { 
      onReleaseResources(oldApps); 
     } 
    } 

    /** 
    * Handles a request to start the Loader. 
    */ 
    @Override 
    protected void onStartLoading() { 
     if (_models != null) { 
      // If we currently have a result available, deliver it 
      // immediately. 
      deliverResult(_models); 
     } 

     if (takeContentChanged() || _models == null) { 
      // If the data has changed since the last time it was loaded 
      // or is not currently available, start a load. 
      forceLoad(); 
     } 
    } 

    /** 
    * Handles a request to stop the Loader. 
    */ 
    @Override 
    protected void onStopLoading() { 
     // Attempt to cancel the current load task if possible. 
     cancelLoad(); 
    } 

    /** 
    * Handles a request to cancel a load. 
    */ 
    @Override 
    public void onCanceled(List<TestItemModel> apps) { 
     super.onCanceled(apps); 

     // At this point we can release the resources associated with 'apps' 
     // if needed. 
     onReleaseResources(apps); 
    } 

    /** 
    * Handles a request to completely reset the Loader. 
    */ 
    @Override 
    protected void onReset() { 
     super.onReset(); 

     // Ensure the loader is stopped 
     onStopLoading(); 

     // At this point we can release the resources associated with 'apps' 
     // if needed. 
     if (_models != null) { 
      onReleaseResources(_models); 
      _models = null; 
     } 
    } 

    /** 
    * Helper function to take care of releasing resources associated with an 
    * actively loaded data set. 
    */ 
    protected void onReleaseResources(List<TestItemModel> apps) { 
    } 

} 

TestItemModel

public class TestItemModel { 

    private String name; 
    private String id; 

    public TestItemModel(String name, String id) { 
     this.name = name; 
     this.id = id; 

    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public String getId() { 
     return id; 
    } 

    public void setId(String id) { 
     this.id = id; 
    } 

} 

請記住，這是所有在測試階段，虛擬的狀態，所以我知道有些事情應該被清理，等等。這是該計劃的一部分，當我得到這個工作。謝謝。

Answer 1

有許多庫，可以幫你出這一點，作爲替代滾動自己。查看Picasso by Square，尋求一種可能的解決方案。

Answer 2

對於使用通用圖像裝載機。它是從網址下載圖像異步一個有效的圖書館。

https://github.com/nostra13/Android-Universal-Image-Loader