在列表视图中显示JSON数据

Question

I am trying to display data fetched from an api. I can display the data as a textview andin a log but I cannot get it to display as a list.

I am getting an error " Cannot resolve constructor "

Error:(72, 68) error: no suitable constructor found for ArrayAdapter(<anonymous FutureCallback<JsonArray>>,int,ArrayList<String>) constructor ArrayAdapter.ArrayAdapter(Context,int,int) is not applicable

Here is the full error code

Error:(72, 68) error: no suitable constructor found for ArrayAdapter(<anonymous FutureCallback<JsonArray>>,int,ArrayList<String>) constructor ArrayAdapter.ArrayAdapter(Context,int,int) is not applicable (argument mismatch; <anonymous FutureCallback<JsonArray>> cannot be converted to Context) constructor ArrayAdapter.ArrayAdapter(Context,int,String[]) is not applicable (argument mismatch; <anonymous FutureCallback<JsonArray>> cannot be converted to Context) constructor ArrayAdapter.ArrayAdapter(Context,int,List<String>) is not applicable (argument mismatch; <anonymous FutureCallback<JsonArray>> cannot be converted to Context)

public class MainActivity extends AppCompatActivity {
ListView lView;
TextView tView;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    lView = (ListView) findViewById(R.id.lv);
    tView = (TextView) findViewById(R.id.textView);

    Ion.with(this).
            load("https://jsonplaceholder.typicode.com/users").
            asJsonArray().
            setCallback(
                    new FutureCallback<JsonArray>()
                    {
                        @Override
                        public void onCompleted(final Exception ex,
                                                final JsonArray array)
                        {
                            if(ex != null)
                            {
                                Toast.makeText(MainActivity.this,
                                        "Error: " + ex.getMessage(),
                                        Toast.LENGTH_LONG).show();
                            }
                            else
                            {
                                ArrayList<String> list = new ArrayList<String>();
                                for(final JsonElement element : array)
                                {
                                    final JsonObject  json;
                                    final JsonElement nameElement;
                                    final JsonElement usernameElement;
                                    final String      name;
                                    final String      username;
                                    json              = element.getAsJsonObject();
                                    nameElement       = json.get("name");
                                    usernameElement   = json.get("username");
                                    name              = nameElement.getAsString();
                                    username          = usernameElement.getAsString();

                                    Log.d("X",
                                            name + " -> " + username);
                                    list.add(name);
                                    list.add(username);
                                    tView.setText(name);
                                }
                                /*  
                              for (int i = 0; i < array.size(); i++) {
                                    list.add(array.get(i).toString());
                                }*/
                                ArrayAdapter<String> adapter = new ArrayAdapter<String>
                                        (this,android.R.layout.simple_list_item_1,list); //ERROR HERE
                                lView.setAdapter(adapter);
                            }

                        }

                    });

}

Answer 1

You have to pass a Context as the first parameter of the Adapter constructor. You pass this , which is not a Context . According to your code, MainActivity.this might work

Answer 2

Remove this in constructor and use MainActivity.this instead. this in your case is instance of anonymous inner class not an Activity(context).