我制作了一个程序，我使用PHP将数据编码为JSON。我的程序运行正常，没有显示任何错误或问题;我得到了我想要的但我面临的问题非常小。
在这里，我无法在ListView中显示项目的图像，但每当我点击其中一个项目行以查看完整项目详细信息时，我都会看到所选项目的图像。这意味着我应该在ListView中获取图像，但我无法证明这一点，那么有人可以帮助解决这个错误吗？
public class AlbumsActivity extends ListActivity {
// Connection detector
ConnectionDetector cd;
// Alert dialog manager
AlertDialogManager alert = new AlertDialogManager();
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
ArrayList<HashMap<String, String>> albumsList;
// albums JSONArray
JSONArray albums = null;
String imagepath;
// albums JSON url
private static final String URL_ALBUMS = "MY URL";
// ALL JSON node names
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_IMAGEPATH = "imagepath";
private static final String TAG_SONGS_COUNT = "songs_count";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_albums);
cd = new ConnectionDetector(getApplicationContext());
// Check for internet connection
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(AlbumsActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Hashmap for ListView
albumsList = new ArrayList<HashMap<String, String>>();
// Loading Albums JSON in Background Thread
new LoadAlbums().execute();
// get listview
ListView lv = getListView();
/**
* Listview item click listener
* TrackListActivity will be lauched by passing album id
* */
lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// on selecting a single album
// TrackListActivity will be launched to show tracks inside the album
Intent i = new Intent(getApplicationContext(), TrackListActivity.class);
// send album id to tracklist activity to get list of songs under that album
String album_id = ((TextView) view.findViewById(R.id.album_id)).getText().toString();
i.putExtra("album_id", album_id);
startActivity(i);
}
});
}
/**
* Background Async Task to Load all Albums by making http request
* */
class LoadAlbums extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AlbumsActivity.this);
pDialog.setMessage("Listing Albums ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting Albums JSON
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_ALBUMS, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Albums JSON: ", "> " + json);
try {
albums = new JSONArray(json);
if (albums != null) {
// looping through All albums
for (int i = 0; i < albums.length(); i++) {
JSONObject c = albums.getJSONObject(i);
// Storing each json item values in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String description = c.getString(TAG_DESCRIPTION);
String imageurl = c.getString(TAG_IMAGEPATH);
String songs_count = c.getString(TAG_SONGS_COUNT);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_DESCRIPTION, description);
map.put(TAG_IMAGEPATH,imageurl);
map.put(TAG_SONGS_COUNT, songs_count);
// adding HashList to ArrayList
albumsList.add(map);
}
}else{
Log.d("Albums: ", "null");
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all albums
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AlbumsActivity.this, albumsList,
R.layout.list_item_albums, new String[]
{
TAG_ID, TAG_NAME, TAG_DESCRIPTION, TAG_IMAGEPATH, TAG_SONGS_COUNT
},
new int[]
{
R.id.album_id, R.id.album_name, R.id.album_description, R.id.list_image, R.id.songs_count
}
);
// updating listview
setListAdapter(adapter);
}
});
}
}
答案 0 :(得分：1)
您必须先下载图像，然后在列表视图中显示它。您无法直接传递图片网址，也无法使用。
答案 1 :(得分：1)
更改当前代码，并从onPostExecute方法中删除runOnUiThread（）：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_albums);
cd = new ConnectionDetector(getApplicationContext());
// Check for internet connection
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(AlbumsActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Hashmap for ListView
albumsList = new ArrayList<HashMap<String, String>>();
// Loading Albums JSON in Background Thread
new LoadAlbums().execute();
}
/**
* Background Async Task to Load all Albums by making http request
* */
class LoadAlbums extends AsyncTask<String, String,
ArrayList<HashMap<String, String>>> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AlbumsActivity.this);
pDialog.setMessage("Listing Albums ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting Albums JSON
* */
protected ArrayList<HashMap<String, String>>
doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_ALBUMS, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Albums JSON: ", "> " + json);
try {
albums = new JSONArray(json);
if (albums != null) {
// looping through All albums
for (int i = 0; i < albums.length(); i++) {
JSONObject c = albums.getJSONObject(i);
// Storing each json item values in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String description = c.getString(TAG_DESCRIPTION);
String imageurl = c.getString(TAG_IMAGEPATH);
String songs_count = c.getString(TAG_SONGS_COUNT);
// creating new HashMap
HashMap<String, String> map = new
HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_DESCRIPTION, description);
map.put(TAG_IMAGEPATH,imageurl);
map.put(TAG_SONGS_COUNT, songs_count);
// adding HashList to ArrayList
albumsList.add(map);
}
}else{
Log.d("Albums: ", "null");
}
} catch (JSONException e) {
e.printStackTrace();
}
return albumsList;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(ArrayList<HashMap<String,
String>> file_url) {
// dismiss the dialog after getting all albums
pDialog.dismiss();
// get listview
ListView lv = getListView();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AlbumsActivity.this, file_url,
R.layout.list_item_albums, new String[]
{
TAG_ID, TAG_NAME, TAG_DESCRIPTION,
TAG_IMAGEPATH, TAG_SONGS_COUNT
},
new int[]
{
R.id.album_id,
R.id.album_name, R.id.album_description, R.id.list_image, R.id.songs_count
}
);
// updating listview
lv.setListAdapter(adapter);
/**
* Listview item click listener
* TrackListActivity will be lauched by passing album id
* */
lv.setOnItemClickListener(new android.widget.
AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// on selecting a single album
Intent i = new Intent(getApplicationContext(),
TrackListActivity.class);
// send album id to tracklist activity to get list of songs
//under that album
String album_id = ((TextView) view.
findViewById(R.id.album_id)).getText().toString();
i.putExtra("album_id", album_id);
startActivity(i);
}
});
}
}
注意：如果您在ImageView中获得直接的网址，那么这将永远不会有效，因为您需要先从网上下载图像，然后将其设置为ImageView src。
请参阅此帖子我们如何从网络服务器获取图片
答案 2 :(得分：1)
这意味着您要使用图像和文本自定义列表视图。为此（我在我的情况下做了什么），获取两个数组中的图像网址和文本。然后通过传递上下文，两个数组来设置列表视图的适配器。
要设置图像，您需要导入库（图像url helper或Universe图像加载器）。两者都可以帮助你，但我会建议你使用图像url helper库，因为它易于使用。
答案 3 :(得分：1)
在您的适配器中试试这个，它可能对您有所帮助：
String imageURL = "htp://domain/some-path/kdhfbdskf.jpg";
Bitmap bmp = null;
try {
InputStream in = new java.net.URL(imageURL).openStream();
bmp = BitmapFactory.decodeStream(in);
}
catch (IOException e) {
e.printStackTrace();
}
if (bmp != null) {
holder.UserImageView.setImageBitmap(bmp);
} else {
holder.UserImageView.setImageResource(R.drawable.ic_launcher);
}
答案 4 :(得分：0)
从执行后执行中删除runOnUiThread（）并且不将UI组件运行到线程中..只需设置图像......