java - 使用类中生成的 Hashmap ArrayList 数据在 MainActivity 的 ListView 中使用？

Question

我正在使用一个类将所有 json 数据添加到 bookList HashMap 数组列表中。现在我需要 MainActivity 上的列表根据引入的数据进行更新。

这似乎是基于我的选择，它正在将所有正确的数据记录到 logcat 中，但 ListView 或结果 View 中没有显示任何内容......我假设我必须返回 bookList HashMap arraylist 返回到 MainActivity 以便以某种方式使用...

MainActivity.java

public class MainActivity extends Activity {

    ArrayList<HashMap<String, String>> bookList;
    Context context;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.search_form);

        context = this;

        list = (ListView) findViewById(R.id.game_list);

 // Possibly this is reading the wrong bookList, so it's not showing the ListView???
        ListAdapter adapter = new SimpleAdapter(context,
                bookList, R.layout.list_view, new String[] {
                        TAG_TITLE, TAG_INFO }, new int[] {
                        R.id.title, R.id.info });

        list.setAdapter(adapter);

        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent,
                    View view, int position, long id) {

                resultsView.setBackgroundColor(Color.DKGRAY);

                resultsView.setText("Book: "
                        + bookList.get(+position).get(TAG_TITLE)
                        + "\n"
                        + "About Book: "
                        + bookList.get(+position).get(TAG_INFO));
            }
        });
    }
}

Json.java

public class Json {

        String TAG_PARENT = "results";
        String TAG_TITLE = "title";
        String TAG_INFO = "info";

    public static ArrayList<HashMap<String, String>> bookList = new ArrayList<HashMap<String, String>>();
            public static void pSearch(String item) {
                String origURL = item;
                URL resultURL;
                try {

                    resultURL = new URL(origURL);

                    Json json = new Json();
                    Json.SnagData gd = json.new SnagData();


                    gd.execute(resultURL);
                } catch (MalformedURLException e) {

                    Log.e("INCORRECT URL", "CHECK URL PASSED");

                    resultURL = null;
                }
            }
        public class SnagData extends AsyncTask<URL, Void, String> {




                protected void onPreExecute() {
                    super.onPreExecute();

                    bookList.clear();

                }

                @Override
                protected String doInBackground(URL... urls) {

                    String fURL = "";
                    for (URL url : urls) {


                        fURL = NetworkConnection.getURLResponse(url);
                    }

                    return fURL;
                }


                protected void onPostExecute(String result) {
                    try {


                        JSONObject json = new JSONObject(result);

                        JSONArray results = json.getJSONArray(TAG_PARENT);

                        int j = results.length();


                        for (int i = 0; i < j; i++) {


                            JSONObject jo = results.getJSONObject(i);


                            String title = jo.getString(TAG_TITLE);
                            String info = jo.getString(TAG_INFO);


                            HashMap<String, String> map = new HashMap<String, String>();

                            map.put(TAG_TITLE, title);
                            map.put(TAG_INFO, info);


                            bookList.add(map);


                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            }
}

Answer 1

使用接口(interface)作为回调

编辑:

public class SnagData extends AsyncTask<URL, Void, String> {
  String TAG_PARENT = "results";
    String TAG_TITLE = "title";
    String TAG_INFO = "info";
    public interface returnListListener
    {
        public void returnList(ArrayList<HashMap<String,String>> list);
    }
    returnListListener mCallback;
public SnagData(Context context)
{
    mCallback = (returnListListener)context;
}

ArrayList<HashMap<String,String>> booklist = new ArrayList<HashMap<String,String>>();
    protected void onPreExecute() {
        super.onPreExecute();

    }

    @Override
    protected String doInBackground(URL... urls) {

        String fURL = "";
        for (URL url : urls) {


            fURL = NetworkConnection.getURLResponse(url);
        }

        return fURL;
    }


    protected void onPostExecute(String result) {
        try {


            JSONObject json = new JSONObject(result);

            JSONArray results = json.getJSONArray(TAG_PARENT);

            int j = results.length();


            for (int i = 0; i < j; i++) {


                JSONObject jo = results.getJSONObject(i);


                String title = jo.getString(TAG_TITLE);
                String info = jo.getString(TAG_INFO);


                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_TITLE, title);
                map.put(TAG_INFO, info);


                bookList.add(map);
                if(mCallback!=null)
                {
                    mCallback.returnList(booklist);
                }


            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

Activity 中

    public class MainActivity extends Activity implements returnListListener
    {
    ListView list;
    URl url; /// initialize your url
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.search_form);
    new SnagData(MainActivity.this).execute(url); // url passed to doInbackgrounf
    list = (ListView) findViewById(R.id.game_list);
    }
     public void returnList(ArrayList<HashMap<String,String>> list)
       {
      // set adapter with list here
      ListAdapter adapter = new SimpleAdapter(MainActivity.this,
            list, R.layout.list_view, new String[] {
                    TAG_TITLE, TAG_INFO }, new int[] {
                    R.id.title, R.id.info });
     list.setAdapter(adapter);

     }
   }

编辑2:

前往评论中的链接 ( https://github.com/woolardjason/JavaTest )

public class MainActivity extends Activity implements returnListListener {
    // Local Variables
    Context context;
    String mTAG = "NETWORK ACTIVITY - MainActivity Class";
    String mUrlString = "http://www.giantbomb.com/api/games/?api_key=84bb1f7ad08b299e6c29992eff7ed6278f406a15&format=json&limit=5&sort=original_release_date:asc&filter=expected_release_year:";
    String[] mReleaseYears;
    public static TextView resultsView;
    ListView mList;
    TextView name;
    TextView deck;
    TextView release;
    Boolean mConnected = false;


    ArrayList<HashMap<String, String>> gameList;
    // Node names from JSON Data
    String TAG_PARENT = "results";
    String TAG_NAME = "name";
    String TAG_DECK = "deck";
    String TAG_RELEASE = "expected_release_year";

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

        // Setting context local var to this activity.
        context = this;
        resultsView = (TextView) findViewById(R.id.results_view);
        // Setting mReleaseYears Local Var to String Array from resources
        mReleaseYears = getResources().getStringArray(R.array.yearArray);
        mList = (ListView) findViewById(R.id.game_list);
        // Creating Spinner Adapter
        ArrayAdapter<String> spinnerAdapter = new ArrayAdapter<String>(context,
                android.R.layout.simple_spinner_item, mReleaseYears);
        spinnerAdapter
                .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // Creating the spinner
        Spinner viewSpinner = (Spinner) findViewById(R.id.release_years);
        // Setting the spinners adapter to created adapter 'spinnerAdapter'
        viewSpinner.setAdapter(spinnerAdapter);
        // Setting
        viewSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
            public void onItemSelected(AdapterView<?> parent, View view,
                    int position, long id) {
                // Setting Local Var Boolean 'mConnected' to the current
                // context's status
                mConnected = NetworkConn.grabConnectionStatus(context);
                // If connected...
                if (mConnected) {
                    // Performing a search using performSearch method based off
                    // current selected spinner position. Passes is data from
                    // array (mReleaseYears) based on selection to allow user
                    // manipulation of data.
                    //Data.performSearch(mUrlString + mReleaseYears[position]);
                    new Data(MainActivity.this).execute(mUrlString+ mReleaseYears[position]);
                    // If not connected...
                } else {
                    // Setting the result's view text
                    resultsView.setText(R.string.networkError);
                    AlertDialog.Builder adb = new AlertDialog.Builder(context);
                    adb.setMessage(R.string.networkError);
                    adb.setCancelable(true);
                    adb.setPositiveButton("Okay", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            dialog.cancel();
                        }
                    });
                    AlertDialog errorAlert = adb.create();
                    errorAlert.show();
                }
            }

            // Method onNothingSelected...self explanatory method not utilized
            // at the moment.
            public void onNothingSelected(AdapterView<?> arg0) {

            }
        });

        // Setting list's item click listener

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


    @Override
    public void returnList(final ArrayList<HashMap<String, String>> list) {
        // TODO Auto-generated method stub
        // set adapter with list here
          ListAdapter adapter = new SimpleAdapter(MainActivity.this,
                list, R.layout.list_view, new String[] {
                        TAG_NAME, TAG_RELEASE }, new int[] {
                        R.id.name, R.id.release });
         mList.setAdapter(adapter);
         mList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                // Method to be called upon item click within list
                public void onItemClick(AdapterView<?> parent,
                        View view, int position, long id) {
                    // Setting the resultsView background color to dark
                    // gray (in case an error occurs, and it's currently
                    // red)
                    resultsView.setBackgroundColor(Color.DKGRAY);
                    // Setting the resultView to display the current
                    // position's (in list) item details based off
                    // pulled in json data thats stored in gameList
                    resultsView.setText("Game: "
                            + list.get(+position).get(TAG_NAME)
                            + "\n"
                            + "About Game: "
                            + list.get(+position).get(TAG_DECK)
                            + "\n"
                            + "Release Year: "
                            + list.get(+position).get(TAG_RELEASE));
                }
            });
    }

}

数据

public class Data extends AsyncTask<String, Void, String> {
    // Node names from JSON Data
    String TAG_PARENT = "results";
    String TAG_NAME = "name";
    String TAG_DECK = "deck";
    String TAG_RELEASE = "expected_release_year";
    static Context context;

    public static ArrayList<HashMap<String, String>> gameList = new ArrayList<HashMap<String, String>>();

    public interface returnListListener
    {
          public void returnList(ArrayList<HashMap<String,String>> list);
    } 
    returnListListener mCallBack;
    public Data(Context context)
    {
       mCallBack = (returnListListener)context;
    }


    // onPreExecute Method - Setting TextView Cars to TextView IDS located
    // in xml
    protected void onPreExecute() {
        super.onPreExecute();
        // Clearing out the GameList (for reloads)
        gameList.clear();

    }

    @Override
    protected String doInBackground(String... urls) {
        // Resetting URL
        String fURL = "";
    //for (URL url : urls) {
            // Setting fURL stringVar to response of getURLReponse method
            // from WebClass class.
            fURL = NetworkConn.getURLResponse(urls[0]);
        //}
        // Returning fURL string var
        return fURL;
    }

    // OnPostExecute method
    protected void onPostExecute(String result) {
        try {
            // Setting json var for type JSONObject to new JSOBObject with
            // passed in string result
            JSONObject json = new JSONObject(result);
            // Setting results JSONArray var to results json node
            JSONArray results = json.getJSONArray(TAG_PARENT);
            // Setting j int var to results array length
            int j = results.length();
            // For conditional cycling through results array grabbing
            // defined nodes and storing them
            for (int i = 0; i < j; i++) {
                // Setting JSONObject var 'jo' to each object within results
                // array
                JSONObject jo = results.getJSONObject(i);

                // Storing pulled in JSON Nodes into separate strings
                String nam = jo.getString(TAG_NAME);
                String dec = jo.getString(TAG_DECK);
                String rel = jo.getString(TAG_RELEASE);

                // Creating HashMap entitled map and initializing it
                HashMap<String, String> map = new HashMap<String, String>();

                // Putting JSON nodes into map
                map.put(TAG_RELEASE, rel);
                map.put(TAG_NAME, nam);
                map.put(TAG_DECK, dec);

                // Adding data to gameList Local var
                gameList.add(map);

                if(mCallBack!=null)
                {
                       mCallBack.returnList(gameList);
                }

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

网络连接

public class NetworkConn {
    static Boolean isConnected = false;
    static String mTAG = "NETWORK ACTIVITY - Webclass Class";
    public static Boolean grabConnectionStatus(Context context){
        checkConnectionStatus(context);
        return isConnected;
    }
    // checkConnectionStatus method
    public static void checkConnectionStatus(Context context) {
        // Obtaining context system service /Connectivity_Service
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        // Obtaining active network info for created connectivitymanager instance
        NetworkInfo networkInfo = cm.getActiveNetworkInfo();
        // checking if networkInfo is null or not
        if (networkInfo != null) {
            // checking if network info is connected
            if (networkInfo.isConnected()) {
                // logging connection type if connected, and networkInfo is not null
                Log.i(mTAG, "connection type: " + networkInfo.getTypeName());
                // setting isConnected to true if connected and networkInfo is not null
                isConnected = true;
            }
        }
    }
    // getURLResponse method
    public static String getURLResponse(String url) {
        // Resetting response var by setting it to equal nothing.
        String response = "";
        try {
            // Initializing URLConnection
            URL url1 = new URL(url);
            URLConnection connection = url1.openConnection();
            // Setting created bufferedinputstring to connection input stream
            BufferedInputStream bis = new BufferedInputStream(
                    connection.getInputStream());
            // Setting contextByte
            byte[] contextByte = new byte[1024];
            // Setting int bytesRead
            int bytesRead = 0;
            // Setting StringBuffer entitled responseBuffer to new StringBuffer
            StringBuffer responseBuffer = new StringBuffer();
            // While conditional to check while bytesRead is
            while ((bytesRead = bis.read(contextByte)) != -1) {
                response = new String(contextByte, 0, bytesRead);
                responseBuffer.append(response);
            }
            response = responseBuffer.toString();
            Log.i(mTAG, response);

        } catch (IOException e) {

            response = "Something happened, no info returned!";
            Log.e(mTAG, "Something happened, no info returned!", e);
        }
        return response;
    }
}

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