我正在尝试制作列表视图。我成功地做到了，没有从URL加载的照片，而无需使用自定义阵列适配器。但是，如何在不使用自定义数组适配器的情况下从URL实现加载图像？
我正在尝试使用此线程的工作代码，但是它给出了 holder 的错误。
错误部分
icon = new ImageDownloaderTask(holder.imageView).execute(doctorPhoto);
doctorsactivity.java
public class DoctorsActivity extends AppCompatActivity {
private JSONArray arrayAdapter;
private static final String URL_FOR_BALANCE = "http://192.168.1.28/api2/doctors.php";
String cancel_req_tag = "login";
private ListView lv;
ArrayList<HashMap<String, String>> contactList;
Bitmap icon = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_doctors);
getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
getSupportActionBar().setCustomView(R.layout.toolbar_doctors);
getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#003764")));
getSupportActionBar().setDisplayHomeAsUpEnabled(false);
SharedPreferences sharedPreferences = getSharedPreferences(Config.SHARED_PREF_NAME, Context.MODE_PRIVATE);
final String pid = sharedPreferences.getString(Config.UID_SHARED_PREF, null);
contactList = new ArrayList<>();
lv = (ListView) findViewById(R.id.list);
StringRequest strReq = new StringRequest(Request.Method.POST,
URL_FOR_BALANCE, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
if (!error) {
JSONArray contacts = jObj.getJSONArray("user");
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String doctorTitle = c.getString("title");
String doctorName = c.getString("first_name");
String doctorSurname = c.getString("last_name");
String doctorPhoto = c.getString("photo"); //image URL
String doctorMobile = c.getString("mobile");
String doctorFullName = doctorTitle+" "+doctorName+" "+doctorSurname;
icon = new ImageDownloaderTask(holder.imageView).execute(doctorPhoto);
// tmp hash map for single contact
HashMap<String, String> contact = new HashMap<>();
// adding each child node to HashMap key => value
contact.put("photo", icon);
contact.put("doctor", doctorFullName);
contact.put("mobile", doctorMobile);
// adding contact to contact list
contactList.add(contact);
}
ListAdapter adapter = new SimpleAdapter(
DoctorsActivity.this, contactList,
R.layout.activity_doctors_list_item, new String[]{"photo", "doctor",
"mobile"}, new int[]{R.id.photo,
R.id.doctor, R.id.mobile});
lv.setAdapter(adapter);
} else {
String errorMsg = jObj.getString("error_msg");
Toast.makeText(getApplicationContext(),
errorMsg, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() {
// Posting params to login url
Map<String, String> params = new HashMap<String, String>();
params.put("uid", pid);
params.put("lang", Locale.getDefault().getDisplayLanguage());
return params;
}
};
// Adding request to request queue
AppSingleton.getInstance(getApplicationContext()).addToRequestQueue(strReq,cancel_req_tag);
}
class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {
private final WeakReference<ImageView> imageViewReference;
public ImageDownloaderTask(ImageView imageView) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(String... params) {
return downloadBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
if (isCancelled()) {
bitmap = null;
}
if (imageViewReference != null) {
ImageView imageView = imageViewReference.get();
if (imageView != null) {
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
Drawable placeholder = null;
imageView.setImageDrawable(placeholder);
}
}
}
}
private Bitmap downloadBitmap(String url) {
HttpURLConnection urlConnection = null;
try {
URL uri = new URL(url);
urlConnection = (HttpURLConnection) uri.openConnection();
final int responseCode = urlConnection.getResponseCode();
if (responseCode != HttpURLConnection.HTTP_OK) {
return null;
}
InputStream inputStream = urlConnection.getInputStream();
if (inputStream != null) {
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
}
} catch (Exception e) {
urlConnection.disconnect();
Log.w("ImageDownloader", "Errore durante il download da " + url);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return null;
}
}
}
为什么不像https://github.com/bumptech/glide一样使用第三方lib？
相关代码：
// ...
new Glide
.with(convertView.getContext())
.load(url)
.centerCrop()
.placeholder(R.drawable.noimage)
.crossFade()
.into(bmImage);
holder.tvName.setText(doctorList.get(position).getName());
holder.tvMobile.setText(doctorList.get(position).getMobile());
// ...
对于每个想要使用图像的listView的人，这是我更正的工作自定义适配器：
public class DoctorAdapter extends ArrayAdapter<Doctors>{
ArrayList<Doctors> doctorList;
LayoutInflater vi;
int Resource;
ViewHolder holder;
public DoctorAdapter(Context context, int resource, ArrayList<Doctors> objects) {
super(context, resource, objects);
vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
Resource = resource;
doctorList = objects;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
holder = new ViewHolder();
v = vi.inflate(Resource, null);
holder.imageview = (ImageView) v.findViewById(R.id.photo);
holder.tvName = (TextView) v.findViewById(R.id.doctor);
holder.tvMobile = (TextView) v.findViewById(R.id.mobile);
holder.callButton = (Button) v.findViewById(R.id.btnCall);
holder.callButton.setTag(holder);
holder.callButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
ViewHolder viewHolder = (ViewHolder) view.getTag();
String message= viewHolder.tvMobile.getText().toString();
Toast.makeText(view.getContext(), message, Toast.LENGTH_SHORT).show();
}
});
v.setTag(holder);
} else {
holder = (ViewHolder) v.getTag();
}
holder.imageview.setImageResource(R.drawable.noimage);
new DownloadImageTask(holder.imageview).execute(doctorList.get(position).getImage());
holder.tvName.setText(doctorList.get(position).getName());
holder.tvMobile.setText(doctorList.get(position).getMobile());
return v;
}
static class ViewHolder {
public ImageView imageview;
public TextView tvName;
public TextView tvMobile;
public Button callButton;
}
private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView bmImage;
public DownloadImageTask(ImageView bmImage) {
this.bmImage = bmImage;
}
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap mIcon = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
mIcon = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return mIcon;
}
protected void onPostExecute(Bitmap result) {
bmImage.setImageBitmap(result);
}
}
}