I am developing a MovieApp which loads movie posters in MainActivity Fragment using AsyncTask background thread. I am using gridview and BaseAdapter to display images. Following is the code.
MainActivityFragment.java :
package com.android.example.cinemaapp.app;
import android.app.Fragment;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
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.AdapterView;
import android.widget.GridView;
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.io.Serializable;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
public class MainActivityFragment extends Fragment{
MoviePosterAdapter moviePosterAdapter;
GridView posterGridView;
public HashMap<String, JSONObject> movieMap;
public MainActivityFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@Override
public void onStart(){
super.onStart();
updateMovies();
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.moviefragment, menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_refresh) {
updateMovies();
}
return super.onOptionsItemSelected(item);
}
public void updateMovies(){
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getActivity());
String sortBy = sharedPreferences.getString(getString(R.string.pref_sort_key), getString(R.string.pref_sort_popular));
new FetchMoviePosterTask().execute(sortBy);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
moviePosterAdapter = new MoviePosterAdapter(getActivity());
posterGridView = (GridView) rootView.findViewById(R.id.gridview_movie);
posterGridView.setAdapter(moviePosterAdapter);
posterGridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
// logic to start detail activity
startActivity(intent);
}
});
return rootView;
}
public class FetchMoviePosterTask extends AsyncTask<String, String, Void> implements Serializable {
@Override
protected Void doInBackground(String... params) {
Log.v("FetchMoviePosterTask", "In background method");
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
String movieJsonStr;
try {
//logic to create uri builder
URL url = new URL(builtUri.toString());
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// Read the input stream into a String
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
// Nothing to do.
movieJsonStr = null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
buffer.append(line + "\n");
}
if (buffer.length() == 0) {
movieJsonStr = null;
}
movieJsonStr = buffer.toString();
// Log.v("MainActivityFragment", "Movie json "+movieJsonStr);
try {
String[] posterPaths = getPosterPaths(movieJsonStr);
for(String path : posterPaths){
publishProgress(path);
}
}catch(JSONException je){
Log.e("MoviePosterPath","Error while parsing JSON");
}
} catch (IOException e) {
Log.e("MoviePosterAdapter", "Error ", e);
movieJsonStr = null;
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("MoviePosterAdapter", "Error closing stream", e);
}
}
}
return null;
}
public String[] getPosterPaths(String movieJsonStr) throws JSONException{
final String POSTER_PATH = //some value
final String POSTER_SIZE = //some value
JSONObject jsonObject = new JSONObject(movieJsonStr);
JSONArray results = jsonObject.getJSONArray("results");
String[] posterStrs = new String[results.length()];
movieMap = new HashMap<String, JSONObject>();
for(int i =0; i < results.length(); i++){
JSONObject movieObj = (JSONObject) results.get(i);
posterStrs[i] = POSTER_PATH + POSTER_SIZE + movieObj.getString("poster_path");
movieMap.put(posterStrs[i], movieObj);
}
return posterStrs;
}
@Override
protected void onProgressUpdate(String... posterValues){
Log.v("FetchMoviePosterTask", "In onProgress method");
moviePosterAdapter.add(posterValues[0]);
super.onProgressUpdate(posterValues);
}
@Override
protected void onPostExecute(Void result) {
Log.v("FetchMoviePosterTask", "In onPostExecute method");
moviePosterAdapter.notifyDataSetChanged();
super.onPostExecute(result);
}
}
}
MoviePosterAdapter.java :
package com.android.example.cinemaapp.app;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
public class MoviePosterAdapter extends BaseAdapter {
ArrayList<String> movieArray = new ArrayList<String>();
private Context mContext;
public MoviePosterAdapter(Context c) {
mContext = c;
}
void add(String path){
movieArray.add(path);
}
void clear(){
movieArray.clear();
}
void remove(int index){
movieArray.remove(index);
}
@Override
public int getCount() {
return movieArray.size();
}
@Override
public Object getItem(int position) {
return movieArray.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
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.setScaleType(ImageView.ScaleType.FIT_XY);
} else {
imageView = (ImageView) convertView;
}
Picasso.with(mContext).load(movieArray.get(position)).into(imageView);
return imageView;
}
}
Problem : When the application is first launched, UI is not getting populated with imageviews. In Logcat I could see control is flowing through doBackground(), onProgressUpdate() and onPostExecute().
When I click 'Refresh' button or If i navigate to some other activity or app and return to Movie app UI (onResume()) it is working perfectly fine. Images are displayed.
Many thanks in advance!
