如何根据JSON对象的结果填充ListView？

Question

私有ListView ListViewGoogle；

private String[] resultArray;

private EditText searchBox;

private Button searchBtn;

private String search_url = "http://ajax.googleapis.com/ajax/services/search/web?v=1.0&q=";

private String search_query;

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

    listViewGoogle = (ListView)findViewById(R.id.listviewgoogle);

    searchBox = (EditText)findViewById(R.id.searchBox);
    searchBtn = (Button)findViewById(R.id.searchBtn);

    searchBtn.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            new JsonSearchTask().execute();

            try
            {
                search_query = search_url + searchBox.getText().toString();

                new JsonSearchTask().execute();

                ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.activity_listviewgoogle, resultArray);
                listViewGoogle.setAdapter(adapter);

            }
            catch (Exception e)
            {
                // TODO: handle exception
            }
        }
    });
}

private class JsonSearchTask extends AsyncTask<Void, Void, Void>
{
    @Override
    protected Void doInBackground(Void... arg0)
    {
        try
        {
            parseResult(sendQuery(search_query));
        }
        catch (JSONException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }
}

private String sendQuery(String query) throws IOException
{
    String queryResult = "";

    URL searchURL = new URL(query);

    HttpURLConnection httpURLConnection = (HttpURLConnection) searchURL.openConnection();

    if (httpURLConnection.getResponseCode() == HttpURLConnection.HTTP_OK)
    {
        InputStreamReader inputStreamReader = new InputStreamReader(httpURLConnection.getInputStream());
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader, 8192);

        String line = null;

        while ((line = bufferedReader.readLine()) != null)
        {
            queryResult += line;
        }

        bufferedReader.close();
    }

    return queryResult;
}

private void parseResult(String json) throws JSONException
{
    String parsedResult = "";

    JSONObject jsonObject = new JSONObject(json);

    JSONObject jsonObject_responseData = jsonObject.getJSONObject("responseData");

    JSONArray jsonArray_results = jsonObject_responseData.getJSONArray("results");

    resultArray = new String[jsonArray_results.length()];

    for(int i = 0; i < jsonArray_results.length(); i++)
    {
        JSONObject jsonObject_i = jsonArray_results.getJSONObject(i);
        parsedResult = "title: " + jsonObject_i.getString("title") + "\n";
        parsedResult += "url: " + jsonObject_i.getString("url") + "\n";
        //parsedResult += "\n";
        resultArray[i] = parsedResult;
    }
}

activity_listviewgoogle.xml:

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/label"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip"
    android:textSize="16dip"
    android:textStyle="bold"
    android:gravity="center" >
</TextView>

activity_my.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="horizontal"
    android:id="@+id/parentOuter" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >

        <EditText
            android:layout_width="fill_parent"
            android:layout_height="match_parent"
            android:hint="type to search..."
            android:layout_weight="2"
            android:id="@+id/searchBox" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Search Me!"
            android:layout_weight="2"
            android:id="@+id/searchBtn" />

        <ListView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/listviewgoogle"
            android:layout_weight="1" />

    </LinearLayout>

</LinearLayout>

Answer 1

你做错了。您调用了AsyncTsk并设置了适配器，如下所示：

new JsonSearchTask().execute();
ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.activity_listviewgoogle, resultArray);
listViewGoogle.setAdapter(adapter);

JSONSearchTask在seperate线程中运行，而ListViewGoogle.setAdapter（适配器）；在获得JSONSearchTask的结果之前在主线程中调用。因此，必须在JSONSearchTask的onPostExecute()方法中调用此方法。

错误：

ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.activity_listviewgoogle, resultArray);

在您的SetonClickListener中。因此，在这个引用OnClickListener的上下文引用，而不是活动的引用。

所以试试

ArrayAdapter adapter = new ArrayAdapter<String>(MainActivity.this, R.layout.activity_listviewgoogle, resultArray);

而不是

ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.activity_listviewgoogle, resultArray);