java - 使用 Jackson Mapper 将 JSON 数据映射到 Java POJO 类，希望在 listview 中获得结果

Question

试图通过意图数据使用杰克逊解析并添加到 pojo 类并返回但无法发送和获取？

主要活动是..

public class MainActivity extends AppCompatActivity {

private Button getButton;
private TextView textView;
private String jsonData;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    setContentView(R.layout.activity_json);
    super.onCreate(savedInstanceState);
    getButton = (Button) findViewById(R.id.getButton);
    textView = (TextView) findViewById(R.id.textView);

    getButton.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
        new  JSONTask().execute("http://192.168.11.75/Headspire/api.php");
        }
    });
}

public class JSONTask extends AsyncTask<String, String, String>
{
    private String json_string = "";
    @Override
    protected String doInBackground(String... params) {
        HttpURLConnection urlConnection = null;
        BufferedReader reader = null;
        try {
            URL url = new URL(params[0]);
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.connect();

            InputStream stream = urlConnection.getInputStream();
            reader = new BufferedReader(new InputStreamReader(stream));
            StringBuffer buffer = new StringBuffer();
            while ((json_string = reader.readLine()) != null) {
                buffer.append(json_string);
            }
            return buffer.toString();
        }
        catch (MalformedURLException e)
        {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(final String result) {
        super.onPostExecute(result);
        textView.setText(result);
        jsonData = result;
    }
    }

    public void parseJSON(View view)
    {
    if (jsonData == null)
    {
        Toast.makeText(getApplicationContext(),
    "Get JSON data first", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Intent intent = new Intent(this, ActivityListView.class);
        intent.putExtra("json_data", jsonData);
        startActivity(intent);
    }
    }
     }

这是我的 ActivityListView 类...

public class ActivityListView extends AppCompatActivity
{

private String jsonData;
private ListView listView;
private PersonAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_list_view);
    listView = (ListView) findViewById(R.id.listView);
    adapter = new PersonAdapter(this, R.layout.row);
    listView.setAdapter(adapter);
    jsonData = getIntent().getExtras().getString("json_data");

    ObjectMapper mapper = new ObjectMapper();
    try
    {
        PersonModel model = mapper.readValue(jsonData, PersonModel.class);
        model.getName();
        model.getId();
        model.getDescription();
        model.getRating();
        adapter.add(model);
    }
    catch (JsonParseException e) {
        e.printStackTrace();
    }

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

我的 PersonAdapeter 类看起来像这样

public class PersonAdapter extends ArrayAdapter
{

private List list = new ArrayList();

public PersonAdapter(Context context, int resource) {
    super(context, resource);
}

@SuppressWarnings("unchecked")
public void add(PersonModel object)
{
    super.add(object);
    list.add(object);
}

@Override
public int getCount()
{
    return list.size();
}
@Override
public Object getItem(int position)
{
    return list.get(position);
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
    View row;
    row = convertView;
    NameHolder nameHolder;
    if (row == null)
    {
        LayoutInflater inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(R.layout.row, parent, false);
        nameHolder = new NameHolder();
        nameHolder.nameTextView = (TextView) row.findViewById(R.id.nameTextView);
        nameHolder.idTextView = (TextView) row.findViewById(R.id.idTextView);
        nameHolder.descriptionTextView = (TextView) row.findViewById(R.id.descriptionTextView);
        nameHolder.ratingTextView = (TextView) row.findViewById(R.id.ratingTextView);
        row.setTag(nameHolder);
    }
    else {
        nameHolder = (NameHolder)row.getTag();
    }
    PersonModel model = (PersonModel) this.getItem(position);
    nameHolder.nameTextView.setText(model.getName());
    nameHolder.idTextView.setText(model.getId());
    nameHolder.descriptionTextView.setText(model.getDescription());
    nameHolder.ratingTextView.setText(model.getRating());

    return row;
}

static class NameHolder
{
    TextView nameTextView, idTextView, descriptionTextView, ratingTextView;
}
}

这是我的 PersonModel 类...

@JsonIgnoreProperties(ignoreUnknown=true)
public class PersonModel extends AppCompatActivity
{

private String name;
private String id;
private String description;
private String rating;

public PersonModel(String name, String id, String description,
String  rating)
{
    this.name = name;
    this.id = id;
    this.description = description;
    this.rating = rating;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getId() {
    return id;
}

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

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public String getRating() {
    return rating;
}

public void setRating(String rating) {
    this.rating = rating;
}

@Override
public String toString()
{
    return "PersonModel [name=" + name + ", id=" + id + ",
description=" + description + ", " +
            "rating=" + rating +"]";
}

}