Java 如何从片段中加载的页面获取JSON数据，并通过asyncbackground调用数据
嗨，我正在尝试显示我从Web服务获取的数据。我通过异步后台管理和获取数据。我正试图显示我通过片段加载的视图listview。请看下面的代码Java 如何从片段中加载的页面获取JSON数据，并通过asyncbackground调用数据,java,android,json,listview,android-fragments,Java,Android,Json,Listview,Android Fragments,嗨，我正在尝试显示我从Web服务获取的数据。我通过异步后台管理和获取数据。我正试图显示我通过片段加载的视图listview。请看下面的代码 this is my MainActivity.java public class MainActivity extends Activity { private DrawerLayout mDrawerLayout; private ListView mDrawerList; private
this is my MainActivity.java
public class MainActivity extends Activity
{
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String[] mActions;
public JSONArray blogData;
public String[] blogPostTitle;
private int position;
@Override
protected void onCreate(Bundle savedInstanceState) {
ListView listView;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
mActions = getResources().getStringArray(R.array.action_array);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
// set a custom shadow that overlays the main content when the drawer opens
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, mActions));
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// enable ActionBar app icon to behave as action to toggle nav drawer
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close /* "close drawer" description for accessibility */
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
}
//public void onItemClick(AdapterView<?> adapter, View view,
// int position, long id) {
// Toast.makeText(getApplicationContext(), ((TextView) view).getText(),
// Toast.LENGTH_SHORT).show();
//}
public void signInClick(View v) {
//Button button = (Button) v;
//startActivity(new Intent(getApplicationContext(), PatientActivity.class));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
//boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
return super.onPrepareOptionsMenu(menu);
}
/* */
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
int pos;
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
// update the main content by replacing fragments
Fragment fragment = new ActionFragment();
Bundle args = new Bundle();
args.putInt(ActionFragment.ARG_ACTION1_NUMBER, position);
fragment.setArguments(args);
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mActions[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggles
mDrawerToggle.onConfigurationChanged(newConfig);
}
}
这是我的MainActivity.java
公共类MainActivity扩展了活动
{
私人抽屉布局mDrawerLayout；
私有列表视图mDrawerList；
私有操作bardrawertoggle mDrawerToggle；
私有字符序列mDrawerTitle；
私有字符序列mTitle；
私有字符串[]符号；
公共JSONArray博客数据；
公共字符串[]blogPostTitle；
私人职位；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
列表视图列表视图；
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
mTitle=mDrawerTitle=getTitle（）；
mActions=getResources（）.getStringArray（R.array.action\u数组）；
mDrawerLayout=（抽屉布局）findViewById（R.id.抽屉布局）；
mDrawerList=（ListView）findViewById（R.id.left\u抽屉）；
//设置抽屉打开时覆盖主要内容的自定义阴影
//mDrawerLayout.setDrawerShadow（R.drawable.drawer\u shadow，GravityCompat.START）；
//使用项目设置抽屉的列表视图，然后单击listener
mDrawerList.setAdapter（新阵列适配器，
R.布局图、抽屉清单（项目、标记）；
setOnItemClickListener（新的DrawerItemClickListener（））；
//启用ActionBar应用程序图标作为切换导航抽屉的操作
getActionBar（）.setDisplayHomeAsUpEnabled（true）；
getActionBar（）.setHomeButtonEnabled（true）；
//ActionBarDrawerToggle将适当的交互连接在一起
//在滑动抽屉和操作栏应用程序图标之间
mDrawerToggle=新操作bardrawertoggle(
此，/*主机活动*/
mDrawerLayout，/*抽屉布局对象*/
R.drawable.ic_抽屉，/*导航抽屉图像替换“Up”插入符号*/
R.string.drawer\u open，/*“open drawer”描述，用于辅助功能*/
R.string.drawer\u close/*“close drawer”可访问性说明*/
) {
公共无效onDrawerClosed（视图）{
getActionBar（）.setTitle（mTitle）；
InvalidateOptions SMenu（）；//创建对OnPrepareOptions SMenu（）的调用
}
打开图纸上的公共空白（视图抽屉视图）{
getActionBar（）.setTitle（mDrawerTitle）；
InvalidateOptions SMenu（）；//创建对OnPrepareOptions SMenu（）的调用
}
};
mDrawerLayout.setDrawerListener（mDrawerToggle）；
如果（savedInstanceState==null）{
选择项目（0）；
}
}
//public void onItemClick（适配器视图适配器、视图、，
//内部位置，长id）{
//Toast.makeText（getApplicationContext（），（（TextView）视图）.getText（），
//吐司。长度（短）。show（）；
//}
公共无效标志单击（视图五）{
//按钮=（按钮）v；
//startActivity（新意图（getApplicationContext（），PatientActivity.class））；
}
@凌驾
公共布尔onCreateOptions菜单（菜单）{
MenuInflater充气机=getMenuInflater（）；
充气机。充气（右菜单。主菜单，菜单）；
返回super.onCreateOptions菜单（菜单）；
}
/*调用InvalidateOptions菜单（）时调用*/
@凌驾
公共布尔值OnPrepareOptions菜单（菜单）{
//如果导航抽屉打开，则隐藏与内容视图相关的操作项
//boolean-DrawerLayout=mDrawerLayout.isDrawerOpen（mDrawerList）；
返回super.onPrepareOptions菜单（菜单）；
}
/* */
@凌驾
公共布尔值onOptionsItemSelected（菜单项项）{
//操作栏home/up操作应打开或关闭抽屉。
//ActionBarDrawerToggle会处理好的。
如果（MDRAWERTOGLE.onOptionsItemSelected（项目））{
返回true；
}
返回super.onOptionsItemSelected（项目）；
}
/*在导航抽屉中单击ListView的侦听器*/
私有类DrawerItemClickListener实现ListView.OnItemClickListener{
int pos；
@凌驾
public void onItemClick（AdapterView父对象、视图、整型位置、长id）{
选择项目（位置）；
}
}
私有void selectItem（内部位置）{
//通过替换片段更新主要内容
Fragment Fragment=新的ActionFragment（）；
Bundle args=新Bundle（）；
args.putInt（ActionFragment.ARG_ACTION1_编号、位置）；
fragment.setArguments（args）；
FragmentManager FragmentManager=getFragmentManager（）；
fragmentManager.beginTransaction（）.replace（R.id.content_frame，fragment.commit（）；
//更新所选项目和标题，然后关闭抽屉
mDrawerList.setItemChecked（位置，true）；
设置标题（位置）；
mDrawerLayout.closeDrawer（mDrawerList）；
}
@凌驾
公共无效设置标题（字符序列标题）{
mTitle=标题；
getActionBar（）.setTitle（mTitle）；
}
/**
*使用ActionBarDrawerToggle时，必须在
*onPostCreate（）和onConfigurationChanged（）。。。
*/
@凌驾
后创建时受保护的无效（Bun
public class ActionFragment extends Fragment
{
public static final String ARG_ACTION1_NUMBER = "Fragment_layout";
public JSONArray blogData;
public String[] blogPostTitle;
public ActionFragment() {
// Empty constructor required for fragment subclasses
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_layout, container, false);
int i = getArguments().getInt(ARG_ACTION1_NUMBER);
if (i == 0)
{
rootView = inflater.inflate(R.layout.fragment_layout, container, false);
}
else if (i == 1) {
rootView = inflater.inflate(R.layout.fragment_articles, container, false);
ListView listview1 = (ListView) rootView.findViewById(R.id.article_list);
ArrayAdapter<String> arrayAdapter1 = new ArrayAdapter<String>(getActivity(), R.layout.layout_listitem, R.id.titleTV, blogPostTitle);
listview1.setAdapter(arrayAdapter1);
} else if (i == 2)
{
rootView = inflater.inflate(R.layout.fragment_news, container, false);
} else if (i == 3) {
rootView = inflater.inflate(R.layout.fragment_signin, container, false);
}
return rootView;
}
public void articleList()
{
if (blogData == null)
{
// TODO: update list when null.
}
else
{
try
{
blogPostTitle = new String[blogData.length()];
for (int i = 0; i < blogData.length(); i++)
{
JSONObject jsonObject = blogData.getJSONObject(i);
String title = jsonObject.getString("title");
title = Html.fromHtml(title).toString();
blogPostTitle[i] = title;
}
} catch (JSONException e) {
Log.e("TAG", "Exception Caught: ", e);
}
}
}
private final MyListener mListener = new MyListener()
{
@Override
public void onComplete(JSONArray result) {
PostController postActivity = new PostController(mListener);
postActivity.execute();
blogData = result;
articleList();
}
};
}
public class PostController extends AsyncTask<Object, Void, JSONArray> {
MyListener mListener;
public PostController(MyListener listenr) {
mListener = listenr;
}
@Override
protected JSONArray doInBackground(Object... arg0)
{
String result = "No data available";
JSONArray jsonResponse = null;
try
{
DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
//TODO: URL ADDRESS for Articles.
HttpGet httpGet = new HttpGet("http://localhost/public/webservices/post");
httpGet.setHeader("Content-type", "application/json");
InputStream inputStream = null;
HttpResponse response = httpclient.execute(httpGet);
HttpEntity entity = response.getEntity();
inputStream = entity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line);
}
result = sb.toString();
jsonResponse = new JSONArray(result);
// TODO: Remove log.
Log.d("TAG", String.valueOf(jsonResponse));
}
catch (MalformedURLException e)
{
Log.e("TAG", "exception caught: ", e);
}
catch (IOException e)
{
Log.e("TAG", "exception caught: ", e);
}
catch (Exception e)
{
Log.e("TAG", "exception caught: ", e);
}
return jsonResponse;
}
@Override
protected void onPostExecute(JSONArray result)
{
mListener.onComplete(result);
}
}
05-08 08:07:27.189 2585-2585/medapp.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: medapp.app, PID: 2585
java.lang.NullPointerException: storage == null
at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
at java.util.Arrays.asList(Arrays.java:155)
at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:141)
at medapp.app.ActionFragment.onCreateView(ActionFragment.java:42)
at android.app.Fragment.performCreateView(Fragment.java:1700)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
at android.app.BackStackRecord.run(BackStackRecord.java:684)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
`public class HomeFragment extends Fragment {
protected ProgressBar mProgressBar;
protected JSONArray blogPostData;
protected String[] blogPostTitle;
ListView listView;
View rootView;
public HomeFragment(){}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView.findViewById(R.id.article_list);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), R.layout.layout_listview_article,R.id.titleTV,blogPostTitle);
listView.setAdapter(adapter);*/
rootView = inflater.inflate(R.layout.fragment_home, container, false);
listView = (ListView) rootView.findViewById(R.id.article_list);
ArticleController articleController = new ArticleController(mListener);
articleController.execute();
return rootView;
}
MyListener mListener = new MyListener(){
@Override
public void onComplete(JSONArray result) {
// TODO: Here you will get the Jsonarray from Asynctask.
// Process it and get the values.
blogPostData = result;
updateArticleList();
ArrayAdapter<String> arrayAdapter1 = new ArrayAdapter<String>(getActivity(), R.layout.layout_listview_article, R.id.titleTV, blogPostTitle);
listView.setAdapter(arrayAdapter1);
}
};
protected void updateArticleList(){
try {
blogPostTitle = new String[blogPostData.length()];
String[] blogPostDate = new String[blogPostData.length()];
String[] blogPostAuthor = new String[blogPostData.length()];
for (int i = 0; i < blogPostData.length(); i++)
{
JSONObject jsonObject = blogPostData.getJSONObject(i);
String title = jsonObject.getString("title");
title = Html.fromHtml(title).toString();
blogPostTitle[i] = title;
String date = jsonObject.getString("date");
title = Html.fromHtml(title).toString();
blogPostTitle[i] = title;
String author = jsonObject.getString("author");
title = Html.fromHtml(title).toString();
blogPostTitle[i] = title;
Log.d("TAG", "Title: " + blogPostTitle);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}`
public class PostActivity extends AsyncTask<Object, Void, JSONArray> {
MyListener mListener;
public PostActivity(MyListener listenr) {
mListener = listenr;
}
@Override
protected JSONArray doInBackground(Object... arg0)
{
// your code
jsonResponse = new JSONArray(result);
return jsonResponse;
}
@Override
protected void onPostExecute(JSONArray result){
mListener.your_callback(result); // send the result back to the fragment,
}
}
public interface MyListener {
public abstract void onComplete(JSONArray result);
}
private final MyListener mListener = new MyListener(){
@Override
public void onComplete(JSONArray result) {
// TODO: Here you will get the Jsonarray from Asynctask.
// Process it and get the values.
blogData = result;
articleList();
}
}
PostActivity postActivity = new PostActivity(mListener);
postActivity.execute();
else if (i == 1) {
rootView = inflater.inflate(R.layout.fragment_articles, container, false);
listview1 = (ListView) rootView.findViewById(R.id.article_list);
PostController postActivity = new PostController(mListener);
postActivity.execute();
}
private final MyListener mListener = new MyListener()
{
@Override
public void onComplete(JSONArray result) {
blogData = result;
articleList();
ArrayAdapter<String> arrayAdapter1 = new ArrayAdapter<String>(getActivity(), R.layout.layout_listitem, R.id.titleTV, blogPostTitle);
listview1.setAdapter(arrayAdapter1);
}
};