读取本地 JSON 文件后的空列表

Question

我想在列表中填充来自本地 JSON 文件的一些消息，但它没有在列表中显示任何消息。有人有什么想法可以帮助我吗？

本地 JSON 文件：

    {
          "events": [
    {
      "event": "Taste of summer"
    },
    {
      "event": " House Party at Millennium Park"
    },
    {
      "event": " Farmers Markets"
    },
    {
      "event": "Blues Festival Preview Events"
    },
    {
      "event": "Cultural Alliance - Heritage and Fashion: At a Global Crossroad?"
    }
        ]
        }

解析 JSON 文件并将其填充到 ListView 中的主要活动：

    public class ListtestActivity extends AppCompatActivity {

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



                // Reading json file from assets folder
                StringBuffer sb = new StringBuffer();
                BufferedReader br = null;
                try {
                    br = new BufferedReader(new InputStreamReader(getAssets().open("listev.json")));
                    String temp;
                    while ((temp = br.readLine()) != null)
                        sb.append(temp);
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if ((br != null)) {
                        try {
                            br.close(); // stop reading
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }

                try {
                    JSONObject jsonObjMain = new JSONObject(sb.toString());
                    JSONArray jsonArray = jsonObjMain.getJSONArray("events");

                    ArrayList<String> messages = new ArrayList<String>();
                    for (int i = 0; i < jsonArray.length(); i++) {
                        // Creating JSONObject from JSONArray
                        JSONObject object = jsonArray.getJSONObject(i);
                       // String message = object.getString("event");
                        String message = jsonArray.getString(i);
                     //I try both but not working!!!
                        messages.add(message);
                    }

                    ArrayAdapter<String> adapter = new ArrayAdapter<String>(ListtestActivity.this,
                            android.R.layout.simple_list_item_1, messages);
                    ListView list = (ListView) findViewById(R.id.listView);
                    list.setAdapter(adapter);
                    list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                        @Override
                        public void onItemClick(AdapterView<?> parent, View view,
                                                int position, long id) {
                            Toast.makeText(ListtestActivity.this, "TEST List View", Toast.LENGTH_SHORT).show();

                        }
                    });

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


        }

带有 ListView 的布局文件：

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.chicago.spice.ListtestActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="events:"
        android:id="@+id/eventView"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/listView"
        android:layout_below="@+id/eventView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp" />
</RelativeLayout>

谢谢。

Answer 1

你必须这样做：

MainActivity

public class MainActivity extends AppCompatActivity {

    ArrayList<String> arrayList=new ArrayList<String>();
    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView=(ListView)findViewById(R.id.live_list_view);

        String json="{\n" +
                "      \"events\": [\n" +
                "{\n" +
                "  \"event\": \"Taste of summer\"\n" +
                "},\n" +
                "{\n" +
                "  \"event\": \" House Party at Millennium Park\"\n" +
                "},\n" +
                "{\n" +
                "  \"event\": \" Farmers Markets\"\n" +
                "},\n" +
                "{\n" +
                "  \"event\": \"Blues Festival Preview Events\"\n" +
                "},\n" +
                "{\n" +
                "  \"event\": \"Cultural Alliance - Heritage and Fashion: At a Global Crossroad?\"\n" +
                "}\n" +
                "    ]\n" +
                "    }";



        try {
            JSONObject jsonRootObject = new JSONObject(json);

            //Get the instance of JSONArray that contains JSONObjects
            JSONArray jsonArray = jsonRootObject.optJSONArray("events");

            if(jsonArray.length()>0) {
                //Iterate the jsonArray and print the info of JSONObjects
                for (int i = 0; i < jsonArray.length(); i++) {
                    JSONObject jsonObject = jsonArray.getJSONObject(i);
                    String data = jsonObject.getString("event");
                    arrayList.add(data);


                }
            }
            else
            {
                Toast.makeText(getApplicationContext(),"No Elements in JsonArray",Toast.LENGTH_SHORT).show();
            }
           // output.setText(data);
        } catch (JSONException e) {e.printStackTrace();}

        ArrayAdapter arrayAdapter=new ArrayAdapter(getApplicationContext(),android.R.layout.simple_list_item_1,arrayList);
        listView.setAdapter(arrayAdapter);

    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.win7.jsonarray.MainActivity">

    <ListView
        android:id="@+id/live_list_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">


    </ListView>
</RelativeLayout>

这会奏效。