我使用PagerSlidingTabStrip library但是这个库有问题。我有一个GridView，当页面发生变化时，AsyncTask会通过 public class SubCategoryActivity extends SherlockFragmentActivity {
static SubCategoryObjectsFragment f;
private PagerSlidingTabStrip tabs;
private ViewPager pager;
private MyPagerAdapter pagerAdapter;
TextView tvCustomTitle;
static List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
static JSONArray jsonArray;
static String url = "http://192.168.1.2/arel/SubCat.php";
static String url2 = "http://192.168.1.2/arel/subCatObject.php";
private static String[][] SubCat;
GridviewAdapter gridAdapter;
static GridView gridViewSubCategory;
HashMap<String, String> map;
static ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
Intent intent;
private class getSubCategoryObjects extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... url) {
// TODO Auto-generated method stub
return BaseActivity.jsonParser.makeHttpRequest(url[0], "POST",
nameValuePairs);
}
@Override
protected void onProgressUpdate(Void... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
try {
jsonArray = new JSONArray(result);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObjet;
map = new HashMap<String, String>();
try {
jsonObjet = jsonArray.getJSONObject(i);
map.put("id", String.valueOf(jsonObjet.getInt("id")));
map.put("title", jsonObjet.getString("title_fa"));
map.put("image", jsonObjet.getString("image"));
map.put("price", jsonObjet.getString("price"));
map.put("date", jsonObjet.getString("date"));
list.add(map);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
gridAdapter = new GridviewAdapter(SubCategoryActivity.this, list);
gridViewSubCategory.setAdapter(gridAdapter);
}
}
private class getSubCategory extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... url) {
// TODO Auto-generated method stub
return BaseActivity.jsonParser.makeHttpRequest(url[0], "POST",
nameValuePairs);
}
@Override
protected void onProgressUpdate(Void... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
try {
jsonArray = new JSONArray(result);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
SubCat = new String[jsonArray.length()][2];
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObjet;
try {
jsonObjet = jsonArray.getJSONObject(i);
SubCat[i][0] = String.valueOf(jsonObjet.getInt("id"));
SubCat[i][1] = jsonObjet.getString("title_fa");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO: handle exception
e.toString();
}
}
pagerAdapter = new MyPagerAdapter(getSupportFragmentManager());
pager.setAdapter(pagerAdapter);
// pager.setCurrentItem(0);
//pager.setOffscreenPageLimit(0);
tabs.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int arg0) {
// TODO Auto-generated method stub
jsonArray = new JSONArray();
list = new ArrayList<HashMap<String, String>>();
nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("getAdvertise", "true"));
nameValuePairs.add(new BasicNameValuePair("subCatId",
SubCat[arg0][0]));
// Activity myActivity = getActivity();
// if (myActivity instanceof SubCategoryActivity) {
new getSubCategoryObjects().execute(url2);
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
// TODO Auto-generated method stub
}
@Override
public void onPageScrollStateChanged(int arg0) {
// TODO Auto-generated method stub
}
});
//jsonArray = new JSONArray();
// final int pageMargin = (int) TypedValue.applyDimension(
// TypedValue.COMPLEX_UNIT_DIP, 16, getResources()
// .getDisplayMetrics());
// pager.setPageMargin(pageMargin);
tabs.setViewPager(pager);
tabs.setTextSize(20);
tabs.setTypeface(BaseActivity.font, Typeface.NORMAL);
// list = new ArrayList<HashMap<String, String>>();
// nameValuePairs = new ArrayList<NameValuePair>();
// nameValuePairs.add(new BasicNameValuePair("getAdvertise", "true"));
// nameValuePairs.add(new BasicNameValuePair("subCatId",
// SubCat[0][0]));
//new getSubCategoryObjects().execute(url2);
}
}
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list);
intent = getIntent();
tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);
pager = (ViewPager) findViewById(R.id.pager);
jsonArray = new JSONArray();
nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("getSubCategory", "true"));
nameValuePairs.add(new BasicNameValuePair("catId", intent
.getStringExtra("id")));
new getSubCategory().execute(url);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowTitleEnabled(false);
getSupportActionBar().setDisplayShowCustomEnabled(true);
tvCustomTitle = new TextView(this);
tvCustomTitle.setText(intent.getStringExtra("title"));
LinearLayout ll = new LinearLayout(this);
LinearLayout.LayoutParams para = new LinearLayout.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
para.setMargins(0, 0, 0, 0); // left,top,right, bottom
para.gravity = Gravity.CENTER_VERTICAL;
tvCustomTitle.setTypeface(BaseActivity.font);
Configuration config = getResources().getConfiguration();
if (Build.VERSION.SDK_INT >= 13) {
if (config.smallestScreenWidthDp >= 600) {
tvCustomTitle.setTextSize(22);
} else {
tvCustomTitle.setTextSize(14);
}
} else {
tvCustomTitle.setTextSize(14);
}
tvCustomTitle.setTextColor(Color.WHITE);
ll.addView(tvCustomTitle, para);
getSupportActionBar().setCustomView(ll);
changeColor(intent.getIntExtra("color", Color.parseColor("#FF666666")));
}
private void changeColor(int newColor) {
tabs.setIndicatorColor(newColor);
// change ActionBar color just if an ActionBar is available
Drawable colorDrawable = new ColorDrawable(newColor);
Drawable bottomDrawable = getResources().getDrawable(
R.drawable.actionbar_bottom);
LayerDrawable ld = new LayerDrawable(new Drawable[] { colorDrawable,
bottomDrawable });
getSupportActionBar().setBackgroundDrawable(ld);
}
/*
* @Override protected void onSaveInstanceState(Bundle outState) {
* super.onSaveInstanceState(outState);
*
* }
*
* @Override protected void onRestoreInstanceState(Bundle
* savedInstanceState) { super.onRestoreInstanceState(savedInstanceState);
*
* }
*/
public static class MyPagerAdapter extends FragmentStatePagerAdapter {
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public CharSequence getPageTitle(int position) {
return SubCat[position][1];
}
@Override
public int getCount() {
return SubCat.length;
}
@Override
public Fragment getItem(int position) {
f = new SubCategoryObjectsFragment();
Bundle b = new Bundle();
b.putString(SubCategoryObjectsFragment.ARG_ID, SubCat[position][0]);
f.setArguments(b);
return f;
}
}
public static class SubCategoryObjectsFragment extends Fragment {
private static final String ARG_ID = "id";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(
R.layout.fragment_sub_category_objects, container, false);
// gridViewSubCategory = new GridView(getActivity());
gridViewSubCategory = (GridView) rootView.findViewById(R.id.gridViewSubCategory);
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
/*
* jsonArray = new JSONArray(); list = new ArrayList<HashMap<String,
* String>>(); nameValuePairs = new ArrayList<NameValuePair>();
* nameValuePairs.add(new BasicNameValuePair("getAdvertise",
* "true")); nameValuePairs.add(new BasicNameValuePair("subCatId",
* getArguments().getString("id")));
*
*
* Activity myActivity = getActivity(); if (myActivity instanceof
* SubCategoryActivity) { ((SubCategoryActivity) myActivity).new
* getSubCategoryObjects().execute(url2); }
*/
// Implement On Item click listener
gridViewSubCategory
.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent,
View view, int position, long id) {
// TODO Auto-generated method stub
BaseActivity.cd = new ConnectionDetector(
getActivity());
BaseActivity.isInternetPresent = BaseActivity.cd
.isConnectingToInternet();
if (BaseActivity.isInternetPresent) {
Intent i = new Intent(getActivity(),
SubCategoryActivity.class);
i.putExtra("id", ((TextView) view
.findViewById(R.id.textViewId))
.getText().toString());
i.putExtra(
"color",
i.getIntExtra("color",
Color.parseColor("#FF666666")));
startActivity(i);
} else {
Toast.makeText(
getActivity(),
"به اینترنت متصل نیستید، به اینترنت متصل شده و دوباره امتحان کنید.",
Toast.LENGTH_SHORT).show();
}
}
});
}
}
public class GridviewAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> list;
HashMap<String, String> tempMap;
public GridviewAdapter(Activity activity,
ArrayList<HashMap<String, String>> list) {
this.activity = activity;
this.list = list;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return list.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater inflator = activity.getLayoutInflater();
View vi = convertView;
if (convertView == null)
vi = inflator.inflate(R.layout.gridview_sub_category_row, null);
TextView id = (TextView) vi.findViewById(R.id.textViewId);
TextView title = (TextView) vi.findViewById(R.id.textViewTitle);
ImageView imageViewSubCat = (ImageView) vi
.findViewById(R.id.imageViewSubCat);
TextView price = (TextView) vi.findViewById(R.id.textViewPrice);
TextView date = (TextView) vi.findViewById(R.id.textViewDate);
RelativeLayout textBackground = (RelativeLayout) vi
.findViewById(R.id.relativeLayoutText);
tempMap = new HashMap<String, String>();
tempMap = list.get(position);
id.setText(tempMap.get("id"));
textBackground.setBackgroundColor(intent.getIntExtra("color",
Color.parseColor("#FF666666")));
title.setText(tempMap.get("title"));
price.setText(tempMap.get("price"));
date.setText(tempMap.get("date"));
title.setTypeface(BaseActivity.font);
price.setTypeface(BaseActivity.font);
date.setTypeface(BaseActivity.font);
// File cachedImg = ImageLoader.getInstance().getDiscCache()
// .get(picUrl + tempMap.get("logo") + ".jpg");
// if (cachedImg.exists())
// cachedImg.delete();
ImageLoader.getInstance().displayImage(
BaseActivity.picUrl + tempMap.get("image") + ".jpg",
imageViewSubCat);
return vi;
}
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
menu.clear();
menu.add("آگهی جدید").setIcon(R.drawable.action_advertise_new)
.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
menu.add("غربال").setIcon(R.drawable.action_search)
.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
menu.add("مرتب سازی").setIcon(R.drawable.action_sort)
.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
}
更新。我的问题是第一页是空的。当我单击选项卡2时，内容显示，但如果我选中选项卡1时单击选项卡3（从选定选项卡移动到选项卡），页面也为空。只有逐一滑动页面或单击“下一个选项卡”（移动一个选项卡形式选择选项卡），它才能正常工作。
为什么页面有时会变空？
库示例应用程序正常工作，但它会在创建时更改视图。我的代码不同，因为网格视图在AsyncTask中通过选择更改页面进行更新。
subCategoryActivity.java ：
的代码 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.astuetz.viewpager.extensions.PagerSlidingTabStrip
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="48dip"
android:background="@drawable/background_tabs" />
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/tabs"
tools:context=".SubCategoryActivity" />
</RelativeLayout>
activity_list.xml 的代码：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="200dp" >
<TextView
android:id="@+id/textViewId"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone" />
<ImageView
android:id="@+id/imageViewSubCat"
android:layout_width="match_parent"
android:layout_height="140dp"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<RelativeLayout
android:id="@+id/relativeLayoutText"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/imageViewSubCat"
android:background="#FF3F9FE0" >
<TextView
android:id="@+id/textViewTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="5dp"
android:gravity="right"
android:text="همه"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/textViewPrice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignRight="@+id/textViewTitle"
android:layout_marginBottom="5dp"
android:layout_toRightOf="@+id/textViewDate"
android:gravity="right"
android:text="20500000 تومان" />
<TextView
android:id="@+id/textViewDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textViewPrice"
android:layout_alignBottom="@+id/textViewPrice"
android:layout_alignParentLeft="true"
android:layout_marginLeft="14dp"
android:text="دقایقی پیش" />
</RelativeLayout>
</RelativeLayout>
</RelativeLayout>
代码：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<GridView
android:id="@+id/gridViewSubCategory"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnWidth="300dp"
android:horizontalSpacing="16dp"
android:numColumns="auto_fit"
android:scrollbars="none"
android:verticalSpacing="16dp" >
</GridView>
</FrameLayout>
代码：
{{1}}
答案 0 :(得分：0)
尝试：
pager.setOffscreenPageLimit(2);
其中2是要保留在当前页面任一侧的内存中的页面数。
答案 1 :(得分：0)
当片段的视图距离当前显示的页面超过一页时，它通常会被销毁。但是，如果您的片段已经显示，它仍然会被创建，但是当它即将显示时，将再次调用onCreateView（）方法。因此，如果将数据存储在局部变量中，则可以检查该局部变量（并且您应该将其状态保存在OnSaveInstanceState（）中，并将它作为savedInstanceState包传递给onCreateView（）方法）然后重新使用缓存的内容填充您的视图。
答案 2 :(得分：0)
简要查看了您的代码，并且：
我没有看到使用'FragmentStatePagerAdapter'而不是正常的原因。请注意，您可以使用support.v4库中的适配器的vanilla实现。
另外，我不理解静态片段'f'的使用，而不是使用Array来提供从pagerAdapter中的'getItem（position）'返回的对象引用。
对于调试，它可以帮助查看ViewPager ...
的源代码scrl到＃800左右并查看'populate（）'和'dataSetChanged（）'，并查看您使用的适配器实现的基类的源代码。
如果您有“黑色”或空白页面，则当VP尝试主动管理保存在内存中以便于滚动的3个相邻页面（默认）时，ViewPager将被适配器送入错误的实例。