如何使用 SimpleAdapter 将下载的图像显示到 ImageView
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【中文标题】如何使用 SimpleAdapter 将下载的图像显示到 ImageView【英文标题】：How to display downloaded image to ImageView with SimpleAdapter 【发布时间】：2017-03-06 13:00:37 【问题描述】：我正在尝试在使用简单适配器创建的 listView 的相应 ImageView 中显示图像。到目前为止，图像可以正常下载到磁盘上的某个位置，并且文本数据在 listView 中显示正常，但我无法将下载的图像显示到 listView 项目的正确位置。到目前为止，我的代码看起来像这样......
public class MainActivity extends ListActivity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// More Code Here
...
productList = new ArrayList<HashMap<String, Object>>();
this.getListView().setOnScrollListener(new EndlessScrollListener()
@Override
public void onLoadMore(int page, int totalItemsCount)
// Triggered only when new data needs to be appended to the list
// Add whatever code is needed to append new items to your
// AdapterView
customLoadMoreDataFromApi(page);
// or customLoadMoreDataFromApi(totalItemsCount);
);
addInitialLoader();
addKeyListener();
// Get listview
lv = getListView();
// Append more data into the adapter
public void customLoadMoreDataFromApi(int offset)
// This method probably sends out a network request and appends new data items to your adapter.
// Use the offset value and add it as a parameter to your API request to retrieve paginated data.
// Deserialize API response and then construct new objects to append to the adapter
//Toast.makeText(MainActivity.this,
//"...loading more items" + offset + "...",
//Toast.LENGTH_LONG).show();
final Toast tost2 = Toast.makeText(MainActivity.this,
"...loading more items" + offset + "...",
Toast.LENGTH_LONG);
tost2.show();
Handler handler2 = new Handler();
handler2.postDelayed(new Runnable()
@Override
public void run()
tost2.cancel();
, 1000);
public void addInitialLoader()
// get Internet status
isInternetPresent = cd.isConnectingToInternet();
// check for Internet status
if (isInternetPresent)
// Internet Connection is Present
// make HTTP requests
new JSONParse().execute();
return;
else
// Internet connection is not present
// Ask user to connect to Internet
showAlertDialog(MainActivity.this,
"No Internet Connection",
"You don't have internet connection.", false);
private class JSONParse extends AsyncTask<String, String, JSONObject>
private ProgressDialog pDialog;
@Override
protected void onPreExecute()
super.onPreExecute();
// Some code Here
...
@Override
protected JSONObject doInBackground(String... args)
JSONParser jParser = new JSONParser();
// Clear previous list items
productList.clear();
// Getting JSON from URL
JSONObject json = jParser.makeHttpRequest(url,
"GET", params);
if (json != null)
try
// Getting JSON Array
Iterator<String> keys = json.keys();
while (keys.hasNext())
String key = keys.next();
String pid = "";
String img = "";
String weight = "";
String name = "";
String desciption = "";
String price = "";
int maxLen = 15;
int maxLen2 = 20;
JSONObject c = json.getJSONObject(key);
String err = c.getString(TAG_ERROR) == "false" ? "" : "true";
if (err == "true")
pid = "0";
img = "0";
weight = "0";
name = "None";
desciption = "none";
price = "none";
else
pid = c.getString(TAG_PID);
img = c.getString(TAG_IMAG);
weight = c.getString(TAG_SIZE);
name = c.getString(TAG_NAME);
desciption = c.getString(TAG_DESCR);
price = c.getString(TAG_PRICE);
// tmp hashmap for single contact
HashMap<String, Object> cartitem = new HashMap<String, Object>();
// adding each child node to HashMap key => value
cartitem.put(TAG_PID, pid);
cartitem.put(TAG_IMAG, R.drawable.logo);
cartitem.put(TAG_IMP, img);
cartitem.put(TAG_SIZE, "Size: " + qty);
cartitem.put(TAG_NAME, name);
cartitem.put(TAG_DESCR, desciption);
cartitem.put(TAG_SIZE, weight);
if (err == "")
cartitem.put(TAG_PRICE, price);
else
cartitem.put(TAG_PRICE,
"Error: No cart to show or items are already delivered.");
// adding product details to product list
productList.add(cartitem);
catch (JSONException e)
Log.e("ERROR Exception: ", e.toString());
e.printStackTrace();
else
// Internet connection is not present
Log.e("ERROR Json: ", "No Internet Available");
return null;
@Override
protected void onPostExecute(JSONObject json)
// protected void onPostExecute(Void result)
super.onPostExecute(json);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
// Keys used in Hashmap
String[] from = TAG_SIZE, TAG_NAME, TAG_DESCR, TAG_PRICE, TAG_PID ;
// Ids of views in listview_layout
int[] to = R.id.size, R.id.name, R.id.descr, R.id.price, R.id.pid ;
ListAdapter adapter = new SimpleAdapter(MainActivity.this,
productList, R.layout.list_item, from, to);
setListAdapter(adapter);
//Log.i("Adapter Count:", ""+adapter.getCount());
for(int i=0;i<adapter.getCount();i++)
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get(TAG_IMP);
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
// HashMap<String, Object> hmDownload = new HashMap<String, Object>();
// Only put images that are set
String needle = "img/nophoto.png";
if(!needle.equals(imgUrl))
hm.put("img_path", imgUrl);
hm.put("position", i);
Log.i("HM:", hm.toString());
imageLoaderTask.execute(hm);
// Starting ImageLoaderTask to download and populate image in the listview
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm)
InputStream iStream=null;
String imgUrl = (String) hm[0].get("img_path");
//imgUrl = imgUrl.replace("\\/", "");
imgUrl = imgrl + imgUrl;
int position = (Integer) hm[0].get("position");
Log.i("IMGURL:", imgUrl);
URL url;
try
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = Environment.getExternalStorageDirectory(); //getBaseContext().getCacheDir();
if (cacheDirectory.canWrite())
File dir = new File (cacheDirectory.getAbsolutePath() + "/IMGDir");
dir.mkdirs();
// Temporary file to store the downloaded image
File tmpFile = new File(dir, "/myimg_"+position+".png");
Log.i("Temp:", cacheDirectory.getAbsolutePath());
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("img",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
Log.i("HMB:", hmBitmap.toString());
// Returning the HashMap object containing the image path and position
return hmBitmap;
catch (Exception e)
e.printStackTrace();
return null;
@Override
protected void onPostExecute(HashMap<String, Object> result)
if(result != null)
// Getting the path to the downloaded image
String path = (String) result.get("img");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Get listview
//lv = getListView();
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter) lv.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
Log.i("POS:", adapter.getItem(position).toString());
// Overwriting the existing path in the adapter
hm.put("image",path);
Log.i("POS 2:", adapter.getItem(position).toString());
// Noticing listview about the dataset changes
//setListAdapter(adapter);
adapter.notifyDataSetChanged();
感谢您在寻找连接方面的任何帮助
提前谢谢你
【问题讨论】：
您的方法似乎有点不合常规...您可以发布您的适配器代码吗？同时，看看这个，看看这里有没有什么对你有帮助：android-developers.blogspot.com/2010/07/…可能是你的ImageView需要知道哪个任务针对它，这样当它被回收时，你就没有竞争了任务。
感谢您的评论...在这种情况下没有适配器代码，因为我已经在扩展 ListActivity... 我也不想偏离这个思路。使用这种特殊方法解决的挑战激励着我 :)
在适配器的从/到映射中，我没有看到对图像/ImageView 的任何引用，所以现在我真的很困惑，我看不到适配器如何绑定图像到 ImageView
我的方法是基于这个 tut wptrafficanalyzer.in/blog/…，虽然他获取 json 数组数据，但我使用的是 json 对象，但本质上适配器更改了新的图像 url 和位置。 tut 也没有显示对 ImageView 的引用，但可以工作。我想知道我哪里出错了。如果我无法做到这一点，那么我将不得不遵循更传统的自定义适配器方法......但我只需要尝试:)
【参考方案1】：
SimpleAdapter 不具备您尝试执行的“滚动查看更多”动态更新的功能。来自文档：
将静态数据映射到 XML 文件中定义的视图的简单适配器。
一旦您传入数据的地图列表，SimpleAdapter 就无法注意到您已更新该列表。
要实现您的目标，您需要创建BaseAdapter 的子类，以便您可以动态添加数据并将图像正确绑定到ImageView。
【讨论】：
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