从ListView将JSON值解析为Activity。 初学者

Question

I just learned java and also android app development.

I've been able to populate json object to a listview from a web-service to my NewActivity.class . but having problems with setting OnItemClickListener for my listview by parsing json value from my jsonparser class to my DetailActivity.class .

I tried reading some answers from here but got lost at some point. I Will be very glad if anyone makes an input. Thanks

JSON PARSER CLASS

public class JSONParser {

public static List<Events> parseFeed(String content) {

    try {
        JSONArray ar = new JSONArray(content);
        List<Events> eventList = new ArrayList<>();

        for (int i = 0; i < ar.length(); i++) {

            JSONObject obj = ar.getJSONObject(i);
            String headline = obj.optString("Content");

            Events events = new Events();

            events.setId(obj.getInt("id"));
            events.setTitle(obj.getString("Title"));
            events.setPostDate(obj.getString("PostDate"));
            events.setSummary(obj.getString("Summary"));
            events.setContent(obj.getString("Content"));
            events.setPicture(obj.getString("Picture"));
            eventList.add(events);
        }

        return eventList;
    } catch (JSONException e) {
        e.printStackTrace();
        return null;
    }

}

This is my NewActivity.class.

public class NewActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

final String LOG = "ListActivity";
private List<Events> eventsList;
private ListView lvEvents;
ProgressBar pb;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_new);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    lvEvents = (ListView) findViewById(R.id.listview1);
    pb = (ProgressBar) findViewById(R.id.progressBar);
    pb.setVisibility(View.INVISIBLE);

    if (isOnline()){
        requestData("http://json/events.php");
    } else {
        Toast.makeText(this, "No Internet Connection", Toast.LENGTH_LONG).show();
    }

}

protected void updateDisplay() {
    EventListAdapter adapter =  new EventListAdapter(this, R.layout.mylist_view, eventsList );
    lvEvents.setAdapter(adapter);
    lvEvents.setOnItemClickListener(this);
}

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Intent intent = new Intent(NewActivity.this, EventsDetail.class);
    intent.putExtra("selectedEvents", eventlist[position]);
    startActivity(intent);
}

private void requestData(String uri){
    MyTask task = new MyTask();
    task.execute(uri);
}

protected boolean isOnline(){
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netinfo = cm.getActiveNetworkInfo();

    if (netinfo != null && netinfo.isConnectedOrConnecting()) {
        return true;
    } else {
        return false;
    }
}

public class MyTask extends AsyncTask<String, String, List<Events>> {

    @Override
    protected void onPreExecute() {
        pb.setVisibility(View.VISIBLE);
    }

    @Override
    protected List<Events> doInBackground(String... params) {

        String data = HttpManager.getData(params[0]);
        eventsList = JSONParser.parseFeed(data);

        for (Events events : eventsList) {

            try {
                String imageUrl = events.getPicture();
                InputStream imageRead = (InputStream) new URL(imageUrl).getContent();
                Bitmap bitmap = BitmapFactory.decodeStream(imageRead);
                events.setBitmap(bitmap);
                imageRead.close();
            } catch (Exception e){
                e.printStackTrace();
            }
        }
        return eventsList;
    }

    @Override
    protected void onPostExecute(List<Events> results) {
        eventsList = results;
        updateDisplay();
        pb.setVisibility(View.INVISIBLE);
    }

}

And this my Events.class

public class Events implements Serializable  {

public int id;
public String Title;
public String PostDate;
public String Summary;
public String Content;
public String Picture;
public Bitmap bitmap;

public String getContent() {
    return Content;
}

public void setContent(String content) {
    Content = content;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public String getPicture() {
    return Picture;
}

public void setPicture(String picture) {
    Picture = picture;
}

public String getPostDate() {
    return PostDate;
}

public void setPostDate(String postDate) {
    PostDate = postDate;
}

public String getSummary() {
    return Summary;
}

public void setSummary(String summary) {
    Summary = summary;
}

public String getTitle() {
    return Title;
}

public void setTitle(String title) {
    Title = title;
}

public Bitmap getBitmap() {
    return bitmap;
}

public void setBitmap(Bitmap bitmap) {
    this.bitmap = bitmap;
}

Lastly my DetailActivity.class which has three TextView to receive the JSON values

public class EventsDetail extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_events_detail);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    TextView detailname = (TextView) findViewById(R.id.detailTitle);
    TextView eventDetail = (TextView) findViewById(R.id.detailContent);
    TextView eventDate = (TextView) findViewById(R.id.detailDate);

 }

Answer 1

You can try this :)

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Intent intent = new Intent(NewActivity.this, EventsDetail.class);

    //try type casting Events instance as Serializable :)
    Events selectedEvent = eventList[position];
    intent.putExtra("selectedEvent",(Serializable)selectedEvent);
    startActivity(intent);
}

This will add selected event as an arguement to your intent :) which is responsible for invoking eventdetail activity :)

and in event detail activity :)

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_events_detail);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    Events passedEvent = getIntent().getSerializableExtra("selectedEvent");

    TextView detailname = (TextView) findViewById(R.id.detailTitle);
    TextView eventDetail = (TextView) findViewById(R.id.detailContent);
    TextView eventDate = (TextView) findViewById(R.id.detailDate);

    //set the textview values now from the recieved events instance :)
}

All being said :) for the above code to work you must implement implements Serializable to your Event class :)

This is very simple :) just requires you to specify implement Serializable and write setter and getter for all the properties of Events class :) Thats all :)

Here is a link for how to implement serialization :) http://www.vogella.com/tutorials/JavaSerialization/article.html

Hope my answer helped you :) Happy coding buddy :)

Answer 2

You need to this way:

1. Make class Serializable

public class Events implements Serializable{

 // Other stuff

}

2. onItemClick of ListView .

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Intent intent = new Intent(NewActivity.this, EventsDetail.class);
    intent.putExtra("object",eventList[position]);
    startActivity(intent);
}

3. EventsDetail class.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_events_detail);

   // Other stuff

    Events event = (Events) getIntent().getSerializableExtra("object");

}

Hope this will help you.