我有一个GridView的ImageAdapter类，它由本地图像填充。我想通过电影数据库api来更新它。这是我的ImageAdapter类-
package jindal5.mayank.popular_movies_14ce10032_gsc;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
public class ImageAdapter extends BaseAdapter {
private Context mContext;
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return mThumbIds.length;
}
public Object getItem(int position) {
return null;
}
public long getItemId(int position) {
return 0;
}
// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) {
// if it's not recycled, initialize some attributes
imageView = new ImageView(mContext);
imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setPadding(8, 8, 8, 8);
} else {
imageView = (ImageView) convertView;
}
imageView.setImageResource(mThumbIds[position]);
return imageView;
}
// references to our images
private Integer[] mThumbIds = {
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7
};
}
这是我的MainActivityFragment，其中包含AsyncTask-
package jindal5.mayank.popular_movies_14ce10032_gsc;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.GridView;
import android.widget.ImageView;
import com.squareup.picasso.Picasso;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
/**
* A placeholder fragment containing a simple view.
*/
public class MainActivityFragment extends Fragment {
private ImageAdapter imag_adap;
public MainActivityFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Add this line in order for this fragment to handle menu events.
setHasOptionsMenu(true);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.menu_fragment, menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_refresh) {
getimage imageTask = new getimage();
imageTask.execute("popularity.desc");
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.fragment_main, container, false);
GridView grid = (GridView) rootview.findViewById(R.id.gridView);
imag_adap = new ImageAdapter(getActivity());
grid.setAdapter(imag_adap);
return rootview;
}
public class getimage extends AsyncTask<String, Void, String[]> {
private final String LOG_TAG = getimage.class.getSimpleName();
public int count;
String[] pos_path;
@Override
protected String[] doInBackground(String... params) {
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
String movieJsonStr = null;
try {
final String movie_url_str = "http://api.themoviedb.org/3/discover/movie?sort_by="+ params[0] +"&api_key=8d7a48043ba1d3348181e2b6615cedc7";
URL movie_url = new URL(movie_url_str);
urlConnection = (HttpURLConnection) movie_url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
return null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
buffer.append(line + "n");
}
if (buffer.length() == 0) {
return null;
}
movieJsonStr = buffer.toString();
Log.v(LOG_TAG, "Forecast string: " + movieJsonStr);
JSONObject movieJson = new JSONObject(movieJsonStr);
JSONArray movieJsonarray = movieJson.getJSONArray("results");
count = movieJsonarray.length();
pos_path = new String[count];
for(int i=0;i<count;i++){
JSONObject sin_movie = movieJsonarray.getJSONObject(i);
pos_path[i] = sin_movie.getString("poster_path");
}
} catch (IOException | JSONException e) {
Log.e(LOG_TAG, "Error ", e);
return null;
}
finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e(LOG_TAG, "Error closing stream", e);
}
}
}
return pos_path;
}
@Override
protected void onPostExecute(String[] result) {
Uri.Builder url_for_poster = new Uri.Builder();
ImageView[] im_vi = new ImageView[count];
for(int j=0;j<count;j++) {
String pos_sin_path = pos_path[j];
Uri.Builder url_build = url_for_poster.scheme("http").authority("image.tmdb.org/t/p").appendPath("w92").appendPath("pos_sin_path");
String url = url_build.toString();
Picasso.with(getActivity()).load("http://image.tmdb.org/t/p/w185//nBNZadXqJSdt05SHLqgT0HuC5Gm.jpg").into(im_vi[j]); **probably this shows target must be null**
//imag_adap.getItem(j) = im_vi[j]; **after uncommenting it shows variable expexted**
}
}
}
}
如下更改适配器，
public class ImageAdapter extends BaseAdapter {
private String drawablePrefix;
private Context mContext;
private ArrayList<String> mThumbUris;
public ImageAdapter(Context c) {
mContext = c;
String packName=mContext.getPackageName();
drawablePrefix="android.resource://" +packName+ "/";
ArrayList<String> uriPaths=new ArrayList<>();// place your drawables.
uriPaths.add(drawablePrefix+ R.drawable.weather);
uriPaths.add(drawablePrefix+ R.drawable.wall_bird);
uriPaths.add(drawablePrefix+ R.drawable.weather);
uriPaths.add(drawablePrefix+ R.drawable.weather);
uriPaths.add(drawablePrefix+ R.drawable.weather);
uriPaths.add(drawablePrefix+ R.drawable.weather);
uriPaths.add(drawablePrefix+ R.drawable.weather);
mThumbUris=uriPaths;
}
public int getCount() {
return mThumbUris.size();
}
public String getItem(int position) {
return mThumbUris.get(position);
}
public long getItemId(int position) {
return 0;
}
// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) {
// if it's not recycled, initialize some attributes
imageView = new ImageView(mContext);
imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setPadding(8, 8, 8, 8);
} else {
imageView = (ImageView) convertView;
}
Uri imgUri=Uri.parse(mThumbUris.get(position));
Picasso.with(mContext)
.load(imgUri)
.placeholder(R.drawable.weather)
.centerCrop()
.resize(400, 400)
.into(imageView);
return imageView;
}
public ArrayList<String> getUriList(){
return mThumbUris;
}
}
更改onPostExecute逻辑如下。
protected void onPostExecute(String[] result) {
Uri.Builder url_for_poster = new Uri.Builder();
ArrayList<String> uriPaths = imag_adap.getUriList();
uriPaths.clear();
for (int j = 0; j < count; j++) {
String pos_sin_path = pos_path[j];
Uri.Builder url_build = url_for_poster.scheme("http").authority("image.tmdb.org/t/p").appendPath("w92").appendPath("pos_sin_path");
String url = url_build.toString();
uriPaths.add(url);
}
imag_adap.notifyDataSetChanged();
}
那么它工作得很好。