Android 尝试在AsyncTask中填充ListView时发生ClassCastException

获取错误：

java.lang.ClassCastException:android.app.Application无法强制转换为android.app.Activity

尝试在

AsyncTask

的

onPostExecute（）

中填充

列表视图时

为什么我会得到这个

活动

public class NotificationsActivity extends Activity {

private static final String FILENAME_NOTIFICATIONS = "notifications.json";

ListView listView;
NotificationsAdapter adapter;
private JSONReader reader;
private ArrayList<Notification> notificationsArray;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_notifications);
    getActionBar().setTitle("");

    reader = new JSONReader(getApplicationContext());

    notificationsArray = new ArrayList<Notification>();

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

    if (Utilities.isNetworkAvailable(getApplicationContext())) { 
        new UpdateNotifications().execute();
    }
    else {
        Toast.makeText(getApplicationContext(), "Network Error: No Connectivity", Toast.LENGTH_SHORT).show();

        if (Utilities.checkIfFileExists(getApplicationContext(), FILENAME_NOTIFICATIONS)) {
            createNotificationsArray();
        }
        else {
            Toast.makeText(getApplicationContext(), "No files found locally. Please connect to the internet and try again.", Toast.LENGTH_LONG).show();
        }
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.notifications, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.action_update:
        if (Utilities.isNetworkAvailable(this)) {
            new UpdateNotifications().execute();
        }
        else {
            Toast.makeText(getApplicationContext(), "Network Error: No Connectivity", Toast.LENGTH_SHORT).show();
        }
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}

private void createNotificationsArray() {
    try { 
        reader.readFromInternal(FILENAME_NOTIFICATIONS);
        notificationsArray = reader.getNotificationsArray();
    } 
    catch (IOException e) { e.printStackTrace(); }
}

private class UpdateNotifications extends AsyncTask<Void, Void, Void> {

    ProgressDialog progressDialog;

    protected void onPreExecute() {
        progressDialog = new ProgressDialog(NotificationsActivity.this);
        progressDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.setMessage("Updating notifications. Please wait.");
        progressDialog.show();
        progressDialog.setCanceledOnTouchOutside(false);
    }

    protected Void doInBackground(Void... params) {
        HTTPGetRequest getRequest = new HTTPGetRequest();
        JSONWriter writer = new JSONWriter(getApplicationContext());

        // Updates local JSON file containing notifications
        String notificationsJsonString = "";
        notificationsJsonString = getRequest.getNotifications();

        try { writer.writeToInternal(FILENAME_NOTIFICATIONS, notificationsJsonString); } 
        catch (IOException e) { e.printStackTrace(); }

        createNotificationsArray();

        Log.v("SIZE", Integer.toString(notificationsArray.size()));

        return null;
    }

    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        progressDialog.dismiss();

        listView = (ListView)findViewById(R.id.notifications_listview);
        adapter = new NotificationsAdapter(getApplicationContext(), R.layout.listview_notification_row, notificationsArray);
        listView.setAdapter(adapter);

        return;
    }
}

在适配器的
getView（）
中，更改此代码

LayoutInflater inflater = ((Activity) context).getLayoutInflater();

到

在适配器中进行更改

 LayoutInflater inflater = ((Activity) context).getLayoutInflater();

与

请参阅：
希望获得此帮助
尝试此代码适配器=新建NotificationsAdapter（NotificationsActivity.this，R.layout.listview\u notification\u row，notificationsArray）；另外，我建议不要使用
getApplicationContext（）
，而是使用
this
或
NotificationsActivity。这
代替了
NotificationsActivity
中的内容。所有这些都可以正常工作了。您能简要解释一下为什么不使用
getApplicationContext（）
？非常感谢。根据SO上关于
上下文的一些帖子，我发现通过使用
getApplicationContext（）
，如果处理不正确，可能会出现内存泄漏。还有，有详细的解释。
LayoutInflater inflater = ((Activity) context).getLayoutInflater();

LayoutInflater inflater = (LayoutInflater) context
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

 LayoutInflater inflater = ((Activity) context).getLayoutInflater();

 LayoutInflater inflater = LayoutInflater.from(context);