Android 带有Asynctask和自定义适配器的ListFragment
我的问题很基本，但我看不出解决办法。这是我在Android上的第三个项目。 到目前为止，我使用的片段中声明了一个ListView，Android 带有Asynctask和自定义适配器的ListFragment,android,android-fragments,android-asynctask,android-listfragment,Android,Android Fragments,Android Asynctask,Android Listfragment,我的问题很基本，但我看不出解决办法。这是我在Android上的第三个项目。 到目前为止，我使用的片段中声明了一个ListView，onCreateView，其中我正在膨胀我的ListView和onActivityCreated来初始化布局。现在我想用ListFragment做同样的事情 我使用此exmaple作为参考： 下面是我用于带有ListView的片段的修改代码。我将此更改为使用ListFragment，但没有成功。有人能帮我吗？先谢谢你 public class PlayersL
onCreateViewonActivityCreated public class PlayersListFragment extends ListFragment {
OnPlayerSelectedListener mCallback;
// URL to make request
private static String URL = Utils.URL;
private static int userID;
ArrayList<HashMap<String, Object>> playersList;
ListView playerView;
private Dialog pDialog;
// The container Activity must implement this interface so the frag can
// deliver messages
public interface OnPlayerSelectedListener {
/** Called by HeadlinesFragment when a list item is selected */
public void onPlayerSelected(int position);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// We need to use a different list item layout for devices older than
// Honeycomb
int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ? android.R.layout.simple_list_item_activated_1
: android.R.layout.simple_list_item_1;
// Create an array adapter for the list view, using the Ipsum headlines
// array
setRetainInstance(true);
new PlayersLoadTask().execute();
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initLayout();
}
public boolean onOptionsItemSelected(MenuItem item) {
return false;
}
private void initLayout() {
if(getActivity().getIntent()!=null) {
userID = getActivity().getIntent().getIntExtra("id", 0);
} else {
return;
}
playerView = (ListView) getActivity().findViewById(R.id.list);
playersList = new ArrayList<HashMap<String, Object>>();
int[] colors = {0, 0xFFFF0000, 0}; // red for the example
}
@Override
public void onStart() {
super.onStart();
// When in two-pane layout, set the listview to highlight the selected
// list item
// (We do this during onStart because at the point the listview is
// available.)
if (getFragmentManager().findFragmentById(R.id.playerDetailFragment) != null) {
getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception.
try {
mCallback = (OnPlayerSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnPlayerSelectedListener");
}
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// Notify the parent activity of selected item
mCallback.onPlayerSelected(position);
// Set the item as checked to be highlighted when in two-pane layout
getListView().setItemChecked(position, true);
}
class PlayersLoadTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
pDialog = ProgressDialog.show(getActivity(), "",
"Loading. Please wait...", true);
}
@Override
protected String doInBackground(String... params) {
try {
ArrayList<BasicNameValuePair> parameters = new ArrayList<BasicNameValuePair>();
parameters.add(new BasicNameValuePair("request", "getPlayers"));
parameters.add(new BasicNameValuePair("clubid", Integer
.toString(userID)));
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(URL);
httpPost.setEntity(new UrlEncodedFormEntity(parameters,
("ISO-8859-1")));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// if this is null the web service returned an empty page
if (httpEntity == null) // response is empty so exit out
return null;
String jsonString = EntityUtils.toString(httpEntity);
if (jsonString != null && jsonString.length() != 0)
{
JSONArray jsonArray = new JSONArray(jsonString);
for (int i = 0; i < jsonArray.length(); i++) {
HashMap<String, Object> map = new HashMap<String, Object>();
JSONObject jsonObject = (JSONObject) jsonArray.get(i);
int id = jsonObject.getInt("id");
String name = jsonObject.getString("name");
map.put("id", id);
map.put("name", name);
playersList.add(map);
}
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
Log.e("ERROR SOMEWHERE!!!! ", e.toString());
}
return null;
}
@Override
protected void onPostExecute(String file_url) {
if (pDialog.isShowing())
pDialog.dismiss();
if (playersList.size() == 0) {
Toast.makeText(getActivity(), "No players in a list",
Toast.LENGTH_SHORT).show();
} else {
playerView.setAdapter(new PlayerListAdapter( // <<== EXCEPTION HERE
getActivity(), R.id.player_list_id,
playersList));
}
}
}
}
在
onactivitycreatedinitLayout（）playerView = (ListView) getActivity().findViewById(R.id.list);
NullPointerException playerView = getListView(); // since you extend ListFragment
这就是我解决问题的方法。似乎您必须在onCreate（）或onActivityCreated（）中包含setListAdapter（）。供日后参考的代码：
public class PlayersListFragment extends ListFragment {
OnPlayerSelectedListener mCallback;
// URL to make request
private static String URL = Utils.URL;
private static int userID;
ArrayList<HashMap<String, Object>> playersList;
ListView playerView;
private ProgressDialog pDialog;
// The container Activity must implement this interface so the frag can
// deliver messages
public interface OnPlayerSelectedListener {
/** Called by HeadlinesFragment when a list item is selected */
public void onPlayerSelected(int position);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
initLayout();
new PlayersLoadTask().execute();
int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ?
android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1;
setListAdapter(new PlayerListAdapter(getActivity(), layout, playersList));
}
public boolean onOptionsItemSelected(MenuItem item) {
return false;
}
private void initLayout() {
if(getActivity().getIntent()!=null) {
userID = getActivity().getIntent().getIntExtra("id", 0);
} else {
return;
}
playerView = getListView();
playersList = new ArrayList<HashMap<String, Object>>();
}
@Override
public void onStart() {
super.onStart();
// When in two-pane layout, set the listview to highlight the selected
// list item
// (We do this during onStart because at the point the listview is
// available.)
if (getFragmentManager().findFragmentById(R.id.playerDetailFragment) != null) {
playerView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception.
try {
mCallback = (OnPlayerSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnPlayerSelectedListener");
}
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// Notify the parent activity of selected item
mCallback.onPlayerSelected(position);
// Set the item as checked to be highlighted when in two-pane layout
playerView.setItemChecked(position, true);
}
class PlayersLoadTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
pDialog = ProgressDialog.show(getActivity(), "",
"Loading. Please wait...", true);
}
@Override
protected String doInBackground(String... params) {
try {
ArrayList<BasicNameValuePair> parameters = new ArrayList<BasicNameValuePair>();
parameters.add(new BasicNameValuePair("request", "getPlayers"));
parameters.add(new BasicNameValuePair("clubid", Integer
.toString(userID)));
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(URL);
httpPost.setEntity(new UrlEncodedFormEntity(parameters,
("ISO-8859-1")));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// if this is null the web service returned an empty page
if (httpEntity == null) // response is empty so exit out
return null;
String jsonString = EntityUtils.toString(httpEntity);
if (jsonString != null && jsonString.length() != 0)
{
JSONArray jsonArray = new JSONArray(jsonString);
for (int i = 0; i < jsonArray.length(); i++) {
HashMap<String, Object> map = new HashMap<String, Object>();
JSONObject jsonObject = (JSONObject) jsonArray.get(i);
int id = jsonObject.getInt("id");
String name = jsonObject.getString("name");
map.put("id", id);
map.put("name", name);
playersList.add(map);
}
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
Log.e("ERROR SOMEWHERE!!!! ", e.toString());
}
return null;
}
@Override
protected void onPostExecute(String file_url) {
if (pDialog.isShowing())
pDialog.dismiss();
if (playersList.size() == 0) {
Toast.makeText(getActivity(), "No players in a list",
Toast.LENGTH_SHORT).show();
} else if(playerView != null) {
setListAdapter(new PlayerListAdapter(getActivity(), R.id.player_list_id, playersList));
/*playerView.setAdapter(new PlayerListAdapter(
getActivity(), R.id.player_list_id,
playersList));*/
}
}
}
公共类PlayersListFragment扩展ListFragment{
OnPlayerSelectedListener McCallback；
//发出请求的URL
私有静态字符串URL=Utils.URL；
私有静态int用户id；
ArrayList玩家列表；
ListView播放视图；
私人对话；
//容器活动必须实现此接口，以便frag能够
//传递信息
PlayerSelectedListener上的公共接口{
/**选择列表项时由HeadlinesFragment调用*/
公共球员当选（国际位置）；
}
@凌驾
已创建ActivityState上的公共无效（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setRetainInstance（真）；
initLayout（）；
新建PlayerLoadTask（）.execute（）；
int layout=Build.VERSION.SDK\u int>=Build.VERSION\u code.h？
android.R.layout.simple_list_item_activated_1:android.R.layout.simple_list_item_1；
setListAdapter（新的PlayerListAdapter（getActivity（），布局，playerList））；
}
公共布尔值onOptionsItemSelected（菜单项项）{
返回false；
}
私有void initLayout（）{
if（getActivity（）.getIntent（）！=null）{
userID=getActivity（）.getIntent（）.getIntExtra（“id”，0）；
}否则{
返回；
}
playerView=getListView（）；
PlayerList=新的ArrayList（）；
}
@凌驾
public void onStart（）{
super.onStart（）；
//在双窗格布局中，将listview设置为高亮显示选定的
//列表项
//（我们在onStart期间执行此操作，因为此时listview
//可用。）
if（getFragmentManager（）.findFragmentById（R.id.playerDetailFragment）！=null）{
playerView.setChoiceMode（ListView.CHOICE\u MODE\u SINGLE）；
}
}
@凌驾
公共事务主任（活动）{
超级转速计（活动）；
//这确保容器活动已实现
//回调接口。如果不是，则抛出异常。
试一试{
mCallback=（OnPlayerSelectedListener）活动；
}catch（ClassCastException e）{
抛出新的ClassCastException（activity.toString（）
+“必须实现OnPlayerSelectedListener”）；
}
}
@凌驾
public void onListItemClick（列表视图l、视图v、整数位置、长id）{
//通知所选项目的父活动
mCallback.onPlayerSelected（位置）；
//将项目设置为选中状态，以便在双窗格布局中高亮显示
playerView.setItemChecked（位置，真）；
}
类PlayerLoadTask扩展了AsyncTask{
@凌驾
受保护的void onPreExecute（）{
pDialog=ProgressDialog.show（getActivity（），“”，
“正在加载。请稍候…”，正确）；
}
@凌驾
受保护的字符串doInBackground（字符串…参数）{
试一试{
ArrayList参数=新的ArrayList（）；
添加（新的BasicNameValuePair（“请求”、“获取玩家”）；
添加（新的BasicNameValuePair（“clubid”），整数
.toString（userID））；
DefaultHttpClient httpClient=新的DefaultHttpClient（）；
HttpPost HttpPost=新的HttpPost（URL）；
httpPost.setEntity（新的UrlEncodedFormEntity）（参数，
（“ISO-8859-1”）；
HttpResponse HttpResponse=httpClient.execute（httpPost）；
HttpEntity HttpEntity=httpResponse.getEntity（）；
//如果为null，则web服务返回一个空页面
如果（httpEntity==null）//响应为空，则退出
返回null；
字符串jsonString=EntityUtils.toString（httpEntity）；
if（jsonString！=null&&jsonString.length（）！=0）
{
JSONArray JSONArray=新的JSONArray（jsonString）；
for（int i=0；ipublic class PlayersListFragment extends ListFragment {
OnPlayerSelectedListener mCallback;
// URL to make request
private static String URL = Utils.URL;
private static int userID;
ArrayList<HashMap<String, Object>> playersList;
ListView playerView;
private ProgressDialog pDialog;
// The container Activity must implement this interface so the frag can
// deliver messages
public interface OnPlayerSelectedListener {
/** Called by HeadlinesFragment when a list item is selected */
public void onPlayerSelected(int position);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
initLayout();
new PlayersLoadTask().execute();
int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ?
android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1;
setListAdapter(new PlayerListAdapter(getActivity(), layout, playersList));
}
public boolean onOptionsItemSelected(MenuItem item) {
return false;
}
private void initLayout() {
if(getActivity().getIntent()!=null) {
userID = getActivity().getIntent().getIntExtra("id", 0);
} else {
return;
}
playerView = getListView();
playersList = new ArrayList<HashMap<String, Object>>();
}
@Override
public void onStart() {
super.onStart();
// When in two-pane layout, set the listview to highlight the selected
// list item
// (We do this during onStart because at the point the listview is
// available.)
if (getFragmentManager().findFragmentById(R.id.playerDetailFragment) != null) {
playerView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception.
try {
mCallback = (OnPlayerSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnPlayerSelectedListener");
}
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// Notify the parent activity of selected item
mCallback.onPlayerSelected(position);
// Set the item as checked to be highlighted when in two-pane layout
playerView.setItemChecked(position, true);
}
class PlayersLoadTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
pDialog = ProgressDialog.show(getActivity(), "",
"Loading. Please wait...", true);
}
@Override
protected String doInBackground(String... params) {
try {
ArrayList<BasicNameValuePair> parameters = new ArrayList<BasicNameValuePair>();
parameters.add(new BasicNameValuePair("request", "getPlayers"));
parameters.add(new BasicNameValuePair("clubid", Integer
.toString(userID)));
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(URL);
httpPost.setEntity(new UrlEncodedFormEntity(parameters,
("ISO-8859-1")));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// if this is null the web service returned an empty page
if (httpEntity == null) // response is empty so exit out
return null;
String jsonString = EntityUtils.toString(httpEntity);
if (jsonString != null && jsonString.length() != 0)
{
JSONArray jsonArray = new JSONArray(jsonString);
for (int i = 0; i < jsonArray.length(); i++) {
HashMap<String, Object> map = new HashMap<String, Object>();
JSONObject jsonObject = (JSONObject) jsonArray.get(i);
int id = jsonObject.getInt("id");
String name = jsonObject.getString("name");
map.put("id", id);
map.put("name", name);
playersList.add(map);
}
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
Log.e("ERROR SOMEWHERE!!!! ", e.toString());
}
return null;
}
@Override
protected void onPostExecute(String file_url) {
if (pDialog.isShowing())
pDialog.dismiss();
if (playersList.size() == 0) {
Toast.makeText(getActivity(), "No players in a list",
Toast.LENGTH_SHORT).show();
} else if(playerView != null) {
setListAdapter(new PlayerListAdapter(getActivity(), R.id.player_list_id, playersList));
/*playerView.setAdapter(new PlayerListAdapter(
getActivity(), R.id.player_list_id,
playersList));*/
}
}
}