我是android的新手。我有一个关于将图像从Json Url加载到ListView的问题。 ListView仅适用于没有图像。
这是我的json网址：
{
"infoBooks": [{
"user_name": "carlo",
"title": "Title: Il potere del cane\nAuthor\/s: Don Winslow",
"author": "",
"urlImage": "https:\/\/books.google.it\/books\/content?id=qiLanQEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api"
}, {
"user_name": "ff",
"title": "Title: Incontro con la storia. Con espansione online. Per la Scuola media\nAuthor\/s: Luisa Benucci",
"author": "",
"urlImage": "https:\/\/books.google.it\/books\/content?id=qTzFSgAACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api"
}]
}
SearchBooks.java：
public class SearchBooks extends AppCompatActivity {
ListView mListView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search_books);
String strUrl = "http://192.168.1.118:8888/webappdb/listViewBooks.php";
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute(strUrl);
mListView = (ListView) findViewById(R.id.listView);
}
private String downloadUrl (String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try {
URL url = new URL(strUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}
data = sb.toString();
br.close();
}catch (Exception e){
Log.d("Exception while downloading url", e.toString());
}finally {
iStream.close();
}
return data;
}
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
@Override
protected String doInBackground(String... url) {
try {
data = downloadUrl(url[0]);
} catch (IOException e) {
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
listViewLoaderTask.execute(result);
}
}
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
@Override
protected SimpleAdapter doInBackground(String... strJson) {
try {
jObject = new JSONObject(strJson[0]);
customAdapter customAdapter = new customAdapter();
customAdapter.parse(jObject);
} catch (JSONException e) {
Log.d("JSON Exception1", e.toString());
}
customAdapter customAdapter = new customAdapter();
List<HashMap<String, Object>> books = null;
try {
books = customAdapter.parse(jObject);
} catch (Exception e){
Log.d("Exception", e.toString());
}
String infoFrom[] = {"user_name", "details", "launcherImage"};
int infoTo[] = {R.id.user_name_search, R.id.bookDescriptionSearch, R.id.coverBookSearch};
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), books, R.layout.row_list_books, infoFrom, infoTo);
return adapter;
}
@Override
protected void onPostExecute(SimpleAdapter adapter) {
mListView.setAdapter(adapter);
for (int i = 0; i < adapter.getCount(); i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("urlImage");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
hm.put("urlImage", imgUrl);
hm.put("position", i);
imageLoaderTask.execute(hm);
}
}
}
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("urlImage");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
iStream = urlConnection.getInputStream();
File cacheDirectory = getBaseContext().getCacheDir();
File tmpFile = new File (cacheDirectory.getPath() + "/wpta_" + position + ".png");
FileOutputStream fOutputStream = new FileOutputStream(tmpFile);
Bitmap b = BitmapFactory.decodeStream(iStream);
b.compress(Bitmap.CompressFormat.PNG, 100, fOutputStream);
fOutputStream.flush();
fOutputStream.close();
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
hmBitmap.put("launcherImage", tmpFile.getPath());
hmBitmap.put("position", position);
return hmBitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
String path = (String) result.get("launcherImage");
int position = (Integer) result.get("position");
SimpleAdapter simpleAdapter = (SimpleAdapter) mListView.getAdapter();
HashMap<String, Object> hm = (HashMap<String, Object>) simpleAdapter.getItem(position);
hm.put("launcherImage", path);
simpleAdapter.notifyDataSetChanged();
}
}
}
customAdapter.java：
public class customAdapter{
public List<HashMap<String, Object>> parse(JSONObject JObject) {
JSONArray infoBooks = null;
try {
infoBooks = JObject.getJSONArray("infoBooks");
} catch (JSONException e) {
e.printStackTrace();
}
return getBooks(infoBooks);
}
private List<HashMap<String, Object>> getBooks(JSONArray infoBooks){
int booksCount = infoBooks.length();
List<HashMap<String, Object>> bookList = new ArrayList<HashMap<String, Object>>();
HashMap<String, Object> book;
for(int i = 0; i < booksCount; i++) {
try {
book = getBook((JSONObject) infoBooks.get(i));
bookList.add(book);
} catch (JSONException e) {
e.printStackTrace();
}
}
return bookList;
}
private HashMap<String, Object> getBook(JSONObject jBook){
HashMap<String, Object> book = new HashMap<String, Object>();
String user_name = "";
String title = "";
String author = "";
String urlImage = "";
try {
user_name = jBook.getString("user_name");
title = jBook.getString("title");
author = jBook.getString("author");
urlImage = jBook.getString("urlImage");
String details = "Title: " + title + "\n" +
"Author/s: " + author;
book.put("user_name", user_name);
book.put("details", details);
book.put("launcherImage", R.mipmap.ic_launcher);
book.put("urlImage", urlImage);
} catch (JSONException e) {
e.printStackTrace();
}
return book;
}
}
logcat：
03-10 12:02:42.088 969-1029/? E/lights: write_led_info failed to open -1
03-10 12:02:42.088 969-1029/? E/lights: write_led_info failed to open -1
03-10 12:02:42.188 969-1065/? E/native: do suspend false
03-10 12:02:42.288 969-1065/? E/WifiStateMachine: WifiStateMachine CMD_START_SCAN source 10007 txSuccessRate=0,00 rxSuccessRate=0,13 targetRoamBSSID=any RSSI=-73
03-10 12:02:42.388 247-569/? E/qdutils: int qdutils::getHDMINode(): Failed to open fb node 2
03-10 12:02:42.388 247-569/? E/qdutils: int qdutils::getHDMINode(): Failed to find HDMI node
03-10 12:02:42.638 969-1104/? E/lights: write_int failed to open -1
03-10 12:02:42.718 969-969/? E/LocSvc_flp: I/===> int flp_inject_location(FlpLocation*) line 222
03-10 12:02:42.728 969-1336/? E/LocSvc_ApiV02: I/<--- void globalRespCb(locClientHandleType, uint32_t, locClientRespIndUnionType, void*) line 125 QMI_LOC_INJECT_POSITION_REQ_V02
03-10 12:02:42.738 969-1367/? E/LocSvc_ApiV02: I/<--- void globalRespCb(locClientHandleType, uint32_t, locClientRespIndUnionType, void*) line 125 QMI_LOC_INJECT_POSITION_REQ_V02
03-10 12:02:43.238 274-763/? E/FastThread: did not receive expected priority boost
03-10 12:02:44.138 969-1104/? E/lights: write_int failed to open -1
03-10 12:02:44.838 969-981/? E/PersonaManagerService: inState(): stateMachine is null !!
03-10 12:02:45.078 270-270/? E/SMD: DCD OFF
03-10 12:02:45.568 23494-23494/gamingproject.sellmybooks E/AndroidRuntime: FATAL EXCEPTION: main
Process: gamingproject.sellmybooks, PID: 23494
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.HashMap.get(java.lang.Object)' on a null object reference
at gamingproject.sellmybooks.SearchBooks$ImageLoaderTask.onPostExecute(SearchBooks.java:216)
at gamingproject.sellmybooks.SearchBooks$ImageLoaderTask.onPostExecute(SearchBooks.java:174)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5536)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1397)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1192)
03-10 12:02:45.578 969-31049/? E/android.os.Debug: ro.product_ship = true
03-10 12:02:45.578 969-31049/? E/android.os.Debug: ro.debug_level = 0x4f4c
03-10 12:02:45.668 2326-31050/? E/SQLiteLog: (284) automatic index on crash_info_summary(package_name_touched)
03-10 12:02:45.728 2326-31050/? E/SQLiteLog: (284) automatic index on crash_info_summary(package_name_touched)
03-10 12:02:48.078 270-270/? E/SMD: DCD OFF
我不理解错误。 提前致谢。
答案 0 :(得分：0)
您无法直接从网址加载图片。 您应该在将其加载到imageview中之前将其转换为drawable。
看一下这个库，在Android中加载图片。 http://square.github.io/picasso/
答案 1 :(得分：0)
为什么你的代码如此复杂？把事情简单化。我有一个演示代码。也许它可以帮到你。只需创建一个您需要的模型类。其他的事情是一样的。
public class MainActivity extends AppCompatActivity {
private Button btnHit;
private HttpURLConnection connection = null;
private URL url;
private BufferedReader reader = null;
private StringBuffer buffer;
private ListView lvMovies;
private ProgressDialog dialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dialog = new ProgressDialog(this);
dialog.setIndeterminate(true);
dialog.setCancelable(false);
dialog.setMessage("Loading !! Please wait..");
DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
.cacheInMemory(true)
.cacheOnDisk(true)
.build();
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getApplicationContext())
.defaultDisplayImageOptions(defaultOptions)
.build();
ImageLoader.getInstance().init(config);
lvMovies = (ListView) findViewById(R.id.lvMovies);
new JSONTask().execute("http://jsonparsing.parseapp.com/jsonData/moviesData.txt");
}
public class JSONTask extends AsyncTask<String, String, List<MovieModel>> {
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog.show();
}
@Override
protected List<MovieModel> doInBackground(String... params) {
try {
url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
String finalJson = buffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("movies");
List<MovieModel> movieModelList = new ArrayList<>();
Gson gson = new Gson();
for (int i = 0; i < parentArray.length(); i++) {
JSONObject finalObject = parentArray.getJSONObject(i);
MovieModel movieModel = gson.fromJson(finalObject.toString(), MovieModel.class);
movieModelList.add(movieModel);
}
return movieModelList;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
@Override
protected void onPostExecute(List<MovieModel> result) {
super.onPostExecute(result);
dialog.dismiss();
MovieAdapter adapter = new MovieAdapter(getApplicationContext(), R.layout.row, result);
lvMovies.setAdapter(adapter);
// TODO Need to set Data on List
}
}
public class MovieAdapter extends ArrayAdapter {
private List<MovieModel> movieModelList;
private int resource;
private LayoutInflater inflater;
public MovieAdapter(Context context, int resource, List<MovieModel> objects) {
super(context, resource, objects);
movieModelList = objects;
this.resource = resource;
inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(resource, null);
holder.ivMovieIcon = (ImageView) convertView.findViewById(R.id.ivIcon);
holder.tvMovie = (TextView) convertView.findViewById(R.id.tvMovie);
holder.tvTagline = (TextView) convertView.findViewById(R.id.tvTagLine);
holder.tvYear = (TextView) convertView.findViewById(R.id.tvYear);
holder.tvDuration = (TextView) convertView.findViewById(R.id.tvDuration);
holder.tvDirector = (TextView) convertView.findViewById(R.id.tvDirector);
holder.rbMovieRating = (RatingBar) convertView.findViewById(R.id.rbMovie);
holder.tvCast = (TextView) convertView.findViewById(R.id.tvCast);
holder.tvStory = (TextView) convertView.findViewById(R.id.tvStory);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
final ProgressBar progressBar = (ProgressBar) convertView.findViewById(R.id.progressBar);
ImageLoader.getInstance().displayImage(movieModelList.get(position).getImage(), holder.ivMovieIcon, new ImageLoadingListener() {
@Override
public void onLoadingStarted(String imageUri, View view) {
progressBar.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
progressBar.setVisibility(View.GONE);
}
@Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
progressBar.setVisibility(View.GONE);
}
@Override
public void onLoadingCancelled(String imageUri, View view) {
progressBar.setVisibility(View.GONE);
}
});
holder.tvMovie.setText(movieModelList.get(position).getMovie());
holder.tvTagline.setText(movieModelList.get(position).getTagline());
holder.tvYear.setText("Year : " + movieModelList.get(position).getYear());
holder.tvDuration.setText(movieModelList.get(position).getDuration());
holder.tvDirector.setText(movieModelList.get(position).getDirector());
// Rating Bar
holder.rbMovieRating.setRating(movieModelList.get(position).getRating() / 2);
Log.v("Rating is", "" + movieModelList.get(position).getRating() / 2);
StringBuffer stringBuffer = new StringBuffer();
for (MovieModel.Cast cast : movieModelList.get(position).getCastList()) {
stringBuffer.append(cast.getName() + ", ");
}
holder.tvCast.setText(stringBuffer);
holder.tvStory.setText(movieModelList.get(position).getStory());
return convertView;
}
class ViewHolder {
private ImageView ivMovieIcon;
private TextView tvMovie;
private TextView tvTagline;
private TextView tvYear;
private TextView tvDuration;
private TextView tvDirector;
private RatingBar rbMovieRating;
private TextView tvCast;
private TextView tvStory;
}
} }
答案 2 :(得分：0)
试试我的适配器代码：
public class MyAdapter extends BaseAdapter implements OnClickListener {
Context con;
ArrayList<Model> mlist;
LayoutInflater inflater=null;
public MyAdapter(Context con,ArrayList<Model> list,SpinnerInterface sp)
{
this.con=con;
this.mlist=list;
inflater=(LayoutInflater)con.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
// UNIVERSAL IMAGE LOADER SETUP
DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
.cacheOnDisc(true).cacheInMemory(true)
.imageScaleType(ImageScaleType.EXACTLY)
.displayer(new FadeInBitmapDisplayer(300)).build();
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(con)
.defaultDisplayImageOptions(defaultOptions)
.memoryCache(new WeakMemoryCache())
.discCacheSize(100 * 1024 * 1024).build();
ImageLoader.getInstance().init(config);
// END - UNIVERSAL IMAGE LOADER SETUP
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return mlist.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return mlist.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public int getViewTypeCount() {
if (getCount() != 0)
return getCount();
return 1;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
model=mlist.get(position);
ViewHolder holder=null;
if(convertView==null){
convertView=inflater.inflate(R.layout.product_layour,parent,false);
holder=new ViewHolder();
holder.img1=(ImageView)convertView.findViewById(R.id.imageViewProductImage);
convertView.setTag(holder);
}else{ holder=(ViewHolder)convertView.getTag(); }
String img_url=model.getPhoto();
ImageLoader imageLoader = ImageLoader.getInstance();
DisplayImageOptions options = new DisplayImageOptions.Builder().cacheInMemory(true)
.cacheOnDisc(true).resetViewBeforeLoading(true)
.showImageForEmptyUri(R.drawable.productimg)
.showImageOnFail(R.drawable.productimg)
.showImageOnLoading(R.drawable.productimg).build();
//download and display image from url
imageLoader.displayImage(img_url,holder.img1, options);
return convertView;
}
private class ViewHolder{
public ImageView img1 ;
}
}
希望它可以帮到你