我已经3 ScreenSlidePageFragment objects。我通过解析json文件来显示我的数据。这是我的主要活动代码：
public class ScheduleMainActivity extends FragmentActivity {
/*
* Parsing JSON to get the array length
*/
private void getLength() {
try {
BufferedReader jsonReader = new BufferedReader(new InputStreamReader(this
.getResources().openRawResource(R.raw.program)));
StringBuilder jsonBuilder = new StringBuilder();
for (String line = null; (line = jsonReader.readLine()) != null;) {
jsonBuilder.append(line).append("\n");
}
JSONTokener tokener = new JSONTokener(jsonBuilder.toString());
JSONArray jsonArray = new JSONArray(tokener);
totalPages = jsonArray.length();
for(int counter = 0 ; counter < NUM_PAGES ; counter ++){
JSONObject jsonObject = jsonArray.getJSONObject(counter);
String getDate = jsonObject.getString("date");
ScheduleItem.dateWay.add(getDate);
}
} catch (Exception e) {
// TODO: handle exception
}
}
public static int totalPages; //value = 3
/**/
/**
* The pager widget, which handles animation and allows swiping horizontally
* to access previous and next wizard steps.
*/
private ViewPager mPager;
/**
* The pager adapter, which provides the pages to the view pager widget.
*/
private PagerAdapter mPagerAdapter;
@Override
public void onBackPressed() {
if (mPager.getCurrentItem() == 0) {
super.onBackPressed();
} else {
mPager.setCurrentItem(mPager.getCurrentItem() - 1);
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_screen_slide);
getLength();
mPager = (ViewPager)findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
supportInvalidateOptionsMenu();
}
});
}
/**
* A simple pager adapter that represents ScreenSlidePageFragment objects,
* in sequence.
*/
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
@Override
public Fragment getItem(int position) {
//Log.e("#MA", position + "");
return ScheduleSlideFragment.create(position, mPager);
}
@Override
public int getCount() {
return totalPages;
}
}
}
现在，我想检查数据date中是否包含先前的ArrayList。所以，我试过这个
if(!ScheduleItem.dateWay.get(getPageNumber).contains(data.get(getPageNumber).getDate())){
jsonParseData(getPageNumber);
}
它抛出IndexOutOfBoundsException: Invalid index 0, size is 0。
这是我的ScheduleSlideFragment代码
public class ScheduleSlideFragment extends Fragment {
final static String ARG_PAGE = "page";
private static ViewPager pager;
private static int pageNumber;
final static int totalPages = ScheduleMainActivity.totalPages;
//@SuppressWarnings("unchecked")
//public List<ScheduleItem>[] data = (ArrayList<ScheduleItem>[])new ArrayList[totalPages];
public ArrayList<ScheduleItem> data = new ArrayList<ScheduleItem>();
public int getPageNumber;
private void jsonParseData(int _getPageNumber) {
try {
BufferedReader jsonReader = new BufferedReader(new InputStreamReader(this
.getResources().openRawResource(R.raw.program)));
StringBuilder jsonBuilder = new StringBuilder();
for (String line = null; (line = jsonReader.readLine()) != null;) {
jsonBuilder.append(line).append("\n");
}
// Parse Json
JSONTokener tokener = new JSONTokener(jsonBuilder.toString());
JSONArray jsonArray = new JSONArray(tokener);
_getPageNumber = getPageNumber;
JSONObject jsonObject = jsonArray.getJSONObject(_getPageNumber);
String getDate = jsonObject.getString("date");
JSONArray getFirstArray = new JSONArray(jsonObject.getString("events"));
for (int i = 0; i < getFirstArray.length(); i++) {
JSONObject getJSonObj = (JSONObject)getFirstArray.get(i);
String time = getJSonObj.getString("time");
//Log.e("Time Log",time);
String type = getJSonObj.getString("type");
String title = getJSonObj.getString("title");
int typeId = getJSonObj.getInt("type_id");
data.add(new ScheduleItem(time, title, typeId, getDate));
/*
* Get Events
*/
if (typeId == 0) {
JSONArray getEventsArray = new JSONArray(getJSonObj.getString("events"));
for (int j = 0; j < getEventsArray.length(); j++) {
JSONObject getJSonEventobj = (JSONObject)getEventsArray.get(j);
int typeEventId = getJSonEventobj.getInt("type_id");
if (typeEventId == 1) {
String EventInfo = getJSonEventobj.getString("info");
String EventType = getJSonEventobj.getString("type");
String EventTitle = getJSonEventobj.getString("title");
String Eventtime = getJSonEventobj.getString("time");
data.add(new ScheduleItem(Eventtime, EventTitle, EventInfo,
typeEventId, getDate));
} else {
String EventType = getJSonEventobj.getString("type");
String EventTitle = getJSonEventobj.getString("title");
String Eventtime = getJSonEventobj.getString("time");
data.add(new ScheduleItem(Eventtime, EventTitle, typeEventId,
getDate));
}
}
}
}
} catch (Exception e) {
Log.getStackTraceString(e);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup)inflater.inflate(R.layout.schedule, container, false);
getPageNumber = pageNumber;
/**
* JSON Parsing
*/
if(!ScheduleItem.dateWay.get(getPageNumber).contains(data.get(getPageNumber).getDate())){
jsonParseData(getPageNumber);
}
/**
* Set header date
*/
((TextView)rootView.findViewById(R.id.tvDay)).setText(data.get(pageNumber).getDate().toString());
final ListView list = (ListView)rootView.findViewById(R.id.list);
BinderData bindingData = new BinderData(this.getActivity(), data);
list.setAdapter(bindingData);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
if (data.get(position).getItemType() == 0
|| data.get(position).getItemType() == 3
|| data.get(position).getItemType() == 2)
return;
Intent intent = new Intent(ScheduleSlideFragment.this.getActivity(),
ContentExtended.class);
intent.putExtra("title", data.get(position).getTitle());
intent.putExtra("content", data.get(position).getContent());
startActivity(intent);
}
});
ImageButton ibLeft = (ImageButton)rootView.findViewById(R.id.ibLeft);
if (pageNumber == 0)
ibLeft.setVisibility(View.INVISIBLE);
else
ibLeft.setVisibility(View.VISIBLE);
ibLeft.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (pager.getCurrentItem() > 0)
pager.setCurrentItem(pager.getCurrentItem() - 1, true);
}
});
ImageButton ibRight = (ImageButton)rootView.findViewById(R.id.ibRight);
if (pageNumber + 1 == totalPages)
ibRight.setVisibility(View.INVISIBLE);
else
ibRight.setVisibility(View.VISIBLE);
ibRight.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (pager.getCurrentItem() < totalPages)
pager.setCurrentItem(pager.getCurrentItem() + 1, true);
}
});
return rootView;
}
public static Fragment create(int position) {
Fragment fragment = new ScheduleSlideFragment();
Bundle args = new Bundle();
args.putInt(ARG_PAGE, position);
fragment.setArguments(args);
return fragment;
}
public static Fragment create(int position, ViewPager _pager) {
pageNumber = position;
pager = _pager;
Fragment fragment = new ScheduleSlideFragment();
Bundle args = new Bundle();
args.putInt(ARG_PAGE, position);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pageNumber = getArguments().getInt(ARG_PAGE);
}
}
我的主要问题是：
数据数组包含每个位置一天/页的所有数据。在当前的实现中（没有If条件），每当有人打开说第3页时，第3页的所有数据都被加载，转换并存储在位置2的数据中。如果我们使用这样的数据数组，则不应重新创建所有的数据。时间。所以，我想使用if condition检查数据是否可用。
我的问题是：
1）有什么方法可以检查data ArrayList是否包含任何数据？
2）如何解决IndexOutOfBoundsException问题？
答案 0 :(得分：2)
1）检查数据ArrayList的方法有哪些替代方法 包含任何数据??
要检查ArrayList是否包含任何数据，请使用isEmpty()方法，如下所示：
ArrayList<ScheduleItem> data = new ArrayList<ScheduleItem>();
if (!data.isEmpty()) { //data is not empty, meaning there is data....
当您尝试使索引位置超出范围时，会抛出2）如何解决
IndexOutOfBoundsException问题？
IndexOutOfBoundsException。
超出范围的时间是[0, size() - 1]，其中size()是ArrayList()的大小。
要简单地检查一下你是否超出界限，做一些这样的事情......
if ( i < 0 || i >= size()) { // Don't get item from an ArrayList, it's out of bounds
在你的情况下：
if ( _getPageNumber >=0 && _getPageNumber < data.size()) { //Get item from jsonArray...
我希望这会有所帮助。
答案 1 :(得分：0)
回答你的问题
1）您可以检查数据是否包含if (data != null && data.size() > 0)
2）您可以通过验证IndexOutOfBoundsException
if (getPageNumber > 0 && getPageNumber < data.size())
答案 2 :(得分：0)
我认为寻找通用Java API的第一个地方是Apache Commons。对于您的特定情况（检查集合是否为空） - 请参阅http://commons.apache.org/proper/commons-collections/javadocs/api-release/org/apache/commons/collections/CollectionUtils.html#isEmpty%28java.util.Collection%29。