Question

我在从JSON .txt文件中提取信息并将该信息显示到ListFragment时遇到了一些困难。

我在资源文件夹中保存.txt文件，其类型为：

{
"cities":
[
  {
    "name":"NAME",
    "state":"STATE",
    "latitude":45.000000,
    "longitude":-102.089016,
  },
  {
    "name":"NAME",
    "state":"STATE",
    "latitude":35.000000,
    "longitude":-102.089016,
  },
  ...
  {
    "name":"NAME",
    "state":"STATE",
    "latitude":15.000000,
    "longitude":-102.089016,
  }
]
}

我正在为以下城市使用公共课：public class City implements Serializable {...} 其中包含每个字段的getter和setter。

我正在尝试使用扩展LoadDataAsyncTask的类AsyncTask<>加载数据：

我认为为了将这些数据加载到ListFragment，我需要在doInBackground()方法中对其进行编码：

@Override
protected Void doInBackground(String... arg0) {
    AssetManager manager = contexto.getAssets();
    JSONArray jarray = null;
    StringBuilder builder = new StringBuilder();

    try {

        BufferedReader reader = new BufferedReader( new InputStreamReader( manager.open("jsonfile.txt") ) );
        String line;
        JSONObject jobject = new JSONObject();
        // Read data
        while((line = reader.readLine()) != null) { 
            builder.append(line);
            String city = jobject.getString("name");

        }
        reader.close();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (JSONException e) {
        Log.e("", e.toString());
    }
    return null;
}

然后有一个类CitiesListFragment包含这样的代码：

public class CitiesListFragment extends ListFragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        ArrayAdapter<City> adapt = new ArrayAdapter<City>(getActivity(),
                    android.R.layout.simple_list_item_1, new ArrayList<City>());

        LoadDataAsyncTask task = new LoadDataAsyncTask(getActivity(), adapt);

        tarea.execute("jsonfile.txt");
        setListAdapter(adaptador);
    }   
}

我想我错过了一些编码，但我不确定在哪里编写它。

Answer 1

您应该在jsonlint.com上查看您的json响应。将json粘贴到那里，看看json的格式是否有效。

如果有效则使用此方法并获得完整的jsonString响应。

 private String readJson() {
        String jsonResponse = null;
        try {
            InputStream inputStream = context.getResources().openRawResource(R.raw.json);

            if (inputStream != null) {
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                String receiveString = "";

                StringBuilder strBuilder = new StringBuilder();
                while ((receiveString = bufferedReader.readLine()) != null) {
                    strBuilder.append(receiveString);
                }
                inputStream.close();

                jsonResponse = strBuilder.toString();
            }
        }
        catch (FileNotFoundException e) {
            Log.e("login activity", "File not found: " + e.toString());
        }
        catch (IOException e) {
            Log.e("login activity", "Can not read file: " + e.toString());
        }
        return jsonResponse;
    }

一旦你有了jsonReponse，只需使用gson或任何其他方法来解析它。

Answer 2

第一：这是我对你的json做的事情：

{
   "cities":[
      {
         "name":"NAME",
         "state":"STATE",
         "latitude":"45.000000",
         "longitude":"-102.089016"
      },
      {
         "name":"NAME",
         "state":"STATE",
         "latitude":"35.000000",
         "longitude":"-102.089016"
      },
      {
         "name":"NAME",
         "state":"STATE",
         "latitude":"15.000000",
         "longitude":"-102.089016"
      },

   ]
}

我将它保存为资源文件夹中的JSON（yourjson.json），以下是我访问它的方式：

首先：只使用活动而不是ListActivity ..您可以在您的情况下使用ListActivity。

public class CitiesListFragment extends Activity {

    ArrayList<String> QuestionForSliderMenu = new ArrayList<String>();

    ArrayList<String> NAME = new ArrayList<String>();
    ArrayList<String> STATE = new ArrayList<String>();
    ArrayList<String> LATITUDE = new ArrayList<String>();
    ArrayList<String> LONGITUDE = new ArrayList<String>();

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.citieslayout);

        ListView listView = (ListView) findViewById(R.id.listview1);

        MyAdapter adapter = new MyAdapter(this, QuestionForSliderMenu);

        listView.setAdapter(adapter);

        try {
            ParsedData();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public void ParsedData() {

        NAME = new ArrayList<String>();
        STATE = new ArrayList<String>();
        LATITUDE = new ArrayList<String>();
        LONGITUDE = new ArrayList<String>();
        try {

            JSONObject json = new JSONObject(loadJSONFromAsset());

            JSONArray array = json.getJSONArray("cities");
            QuestionForSliderMenu = new ArrayList<String>();
            Log.d("Cities: ", array.toString());
            for (int my = 0; my <= array.length(); my++) {

                JSONObject c = array.getJSONObject(my);

                String name = c.getString("name");
                String state = c.getString("state");
                String latitude = c.getString("latitude");
                String longitude = c.getString("longitude");

                  NAME.add(name);
                  STATE.add(state);
                  LATITUDE.add(latitude);
                  LONGITUDE.add(longitude);

            }

        } catch (JSONException e) {

            e.printStackTrace();

        }

    }

    private class MyAdapter extends BaseAdapter {

        private int lastPosition = -1;
        private Context context;
        private ArrayList<ModelClass> name;
        private ArrayList<ModelClass> state;
        private ArrayList<ModelClass> latitude;
        private ArrayList<ModelClass> longitude;
        private ArrayList<ModelClass> MainItems;
        private ArrayList<String> mainList;

        public MyAdapter(Context context, ArrayList<ModelClass> name,
                ArrayList<ModelClass> state, ArrayList<ModelClass> latitude,
                ArrayList<ModelClass> longitude) {
            super();
            this.context = context;
            this.name = name;
            this.state = state;
            this.latitude = latitude;
            this.longitude = longitude;
        }

        public MyAdapter(Context applicationContext,
                ArrayList<String> questionForSliderMenu1) {

            super();

            this.mainList = questionForSliderMenu1;

        }

        @Override
        public int getCount() {

            return STATE.size();
        }

        @Override
        public Object getItem(int position) {

            return position;
        }

        @Override
        public long getItemId(int position) {

            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if (convertView == null) {

                LayoutInflater inflater = (LayoutInflater) getApplicationContext()
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(R.layout.cities_row, null);
            }

            TextView name = (TextView) convertView.findViewById(R.id.Name);
            TextView state = (TextView) convertView.findViewById(R.id.State);
            TextView latitude = (TextView) convertView
                    .findViewById(R.id.Latitude);
            TextView longitude = (TextView) convertView
                    .findViewById(R.id.Longitude);

            try {
                name.setText(NAME.get(position));
                state.setText(STATE.get(position));
                latitude.setText(LATITUDE.get(position));
                longitude.setText(LONGITUDE.get(position));
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            return convertView;
        }

    }

//这是我从资源获取json的地方，在上面的方法中只使用此方法获取json对象。

public String loadJSONFromAsset() {

            String json = null;

            try {

                InputStream is = getApplicationContext().getAssets().open(
                        "yourjson.json");

                int size = is.available();

                byte[] buffer = new byte[size];

                is.read(buffer);

                is.close();

                json = new String(buffer, "UTF-8");

            } catch (IOException ex) {

                ex.printStackTrace();

                return null;
            }
            return json;

        }

    }

这就是全部。最后，布局：

cities_row.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/Name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Cities"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/State"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="States"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/Latitude"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Latitude"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/Longitude"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Longitude"
        android:textAppearance="?android:attr/textAppearanceMedium" />

</LinearLayout>

并且，citieslayout.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"

    tools:context=".MainActivity" >

    <ListView
        android:id="@+id/listview1"
        android:layout_width="match_parent"
        android:layout_height="338dp"
        android:layout_weight="0.36" 
        android:background="#333333">
    </ListView>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button" />

</LinearLayout>

希望这会有所帮助.. :)

从JSON.txt文件解析为ListFragment

2 个答案: