我有一个带有适配器的 ListFragment 和一个 AsyncTask 来加载数据，目前它建立了一个带有文本的列表视图，我现在已经将一个非动态图像作为占位符。我想知道是否有人可以阐明实现从网络下载图像的最佳方法，我有 url 可以从谷歌测试，并通过适配器缓存和显示这些图像，我还没有滚动监听器到达底部，但我有点坚持传递和加载我的动态图像的最佳解决方案是，如果有人能告诉我加载图像的最佳方法并最好缓存它们，所以我不必下载它们每次都到sd卡和所有东西。
这是我的课
测试列表片段
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) {
}
}
测试项目模型
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;
}
}
请记住，这一切都处于测试阶段，处于虚拟状态，所以我知道应该清理一些东西，等等。当我开始工作时，这都是计划的一部分。谢谢。