我的应用程序从Web服务中提取数据，该Web服务为每个用户生成不同的部分。然后，我将使用这些部分使用FragmentPagerAdapter创建选项卡。
我使用了异步任务从Web服务中提取数据。但是，在我的异步任务之前执行了FragmentPagerAdapter中的诸如getCount（）和getPageTitle（）之类的重写方法，并完成了其工作。如何防止这种情况，并根据从Web服务获取的数据动态生成选项卡及其标题名称？
换句话说，如何基于从Web服务获取的数据来创建动态数量的标签和标题
我的FragmentPagerAdapter代码如下。如您所见，我对选项卡的数量及其标题名称进行了硬编码。
public class SectionsPagerAdapter extends FragmentPagerAdapter{
private boolean proceedStatus = false;
private String requestURL = "xxxxxxxxxxxxxxxxxxxxxxxx";
//list of fragments need to be added dynamically
public final ArrayList<Fragment> screens = new ArrayList<Fragment>();
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
Fragment fragment = new SectionFragment();
Bundle args = new Bundle();
args.putInt(SectionFragment.ARG_SECTION_NUMBER, position + 1);
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return "Camera".toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
case 3:
return "SECTION 4";
}
return null;
}
//setting the section title
private void setSectionTitle(){
}
//count the number of sections
private int countNumberofSections(){
int numberOfSection = 0;
return numberOfSection;
}
}
然后我有下面的片段代码，其中有异步任务的调用者
public static class SectionFragment extends Fragment implements OnTaskCompleted {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private Slider adapter;
private ViewPager viewPager;
public static final String ARG_SECTION_NUMBER = "section_number";
Button thumbUpBut;
Button thumbDownBut;
Button captureButton;
ImageView genImage;
TextView genCaption;
private Camera mCamera;
private CameraPreview mPreview;
private static File mediaFile;
private ProgressDialog progress;
private static String imageSaveLocation;
private static String file_name_without_extension;
private ImageView imageView;
private Button uploadButton;
private Button cancelButton;
private Collection<Place> places = null;
private Collection<Happenings> events = null;
private Collection<General> general = null;
private ArrayList<String> sections;
public int getNumberOfPages(){
return sections.size();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main_dummy,container, false);
TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
FeedRequest task = new FeedRequest(this);
task.execute("xxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
captureButton = (Button) rootView.findViewById(R.id.button_capture);
captureButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
takePhoto();
}
});
thumbUpBut = (Button) rootView.findViewById(R.id.thumbUp);
thumbUpBut.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Log.v("thumbPress", "thumbPressUp");
thumb("up");
}
});
thumbDownBut = (Button) rootView.findViewById(R.id.thumbDown);
thumbDownBut.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Log.v("thumbPress", "thumbPressDown");
thumb("down");
}
});
//allocating the activity one to the camera
if(getArguments().getInt(ARG_SECTION_NUMBER) == 1){
mCamera = getCameraInstance();
mPreview = new CameraPreview(this.getActivity(), mCamera);
FrameLayout preview = (FrameLayout)rootView.findViewById(R.id.camera_preview);
preview.addView(mPreview);
//hide buttons
thumbDownBut.setVisibility(rootView.INVISIBLE);
thumbUpBut.setVisibility(rootView.INVISIBLE);
}else{
thumbDownBut.setVisibility(rootView.VISIBLE);
thumbUpBut.setVisibility(rootView.VISIBLE);
captureButton.setVisibility(rootView.INVISIBLE);
}
viewPager = (ViewPager) rootView.findViewById(R.id.pager);
return rootView;
}
//take photo function
private void takePhoto() {
//get coordinates of the location
UserLocation userLocation = new UserLocation();
userLocation.getUserLocation(getActivity());
coordinates[0] = userLocation.longitude;
coordinates[1] = userLocation.latitude;
PictureCallback pictureCB = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera cam) {
new SavePhotoAndMetadata().execute(data);
cam.startPreview();
}
};
mCamera.takePicture(null, null, pictureCB);
}
//get camera instance
private Camera getCameraInstance() {
Camera camera = null;
try {
camera = Camera.open();
} catch (Exception e) {
// cannot get camera or does not exist
}
return camera;
}
//get the media out
private static File getOutputMediaFile() {
File mediaStorageDir = new File(Environment.getExternalStorageDirectory() + "/Android/data/asia.ceynet.realsnap/temp_img");
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d("MyCameraApp", "failed to create directory");
return null;
}
}
// Create a media file name
String timeStamp = (DateFormat.format("dd-MM-yyyy hh:mm:ss", new java.util.Date()).toString());
mediaFile = new File(mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp + ".jpg");
file_name_without_extension = "IMG_" + timeStamp;
imageSaveLocation = mediaFile.toString();
return mediaFile;
}
//saving the image and metadata together
class SavePhotoAndMetadata extends AsyncTask<byte[], String, String> {
@Override
protected String doInBackground(byte[]... data) {
File picFile = getOutputMediaFile();
if (picFile == null) {
return null;
}
byte[] photoData = data[0];
try {
//save the image
FileOutputStream fos = new FileOutputStream(picFile);
fos.write(photoData);
fos.close();
} catch (FileNotFoundException e) {
e.getStackTrace();
} catch (IOException e) {
e.getStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
progress = new ProgressDialog(getActivity());
progress.setMessage("Saving Picture..Please wait...");
progress.show();
}
@Override
protected void onPostExecute(String s) {
progress.dismiss();
imagePreviewDialog();
}
}
//save image metadata in async task
class SaveMetadataTask extends AsyncTask<Void, String, Void> {
@Override
protected Void doInBackground(Void... params) {
serializeDeserialize.serializeData("This is for testing", file_name_without_extension, Double.toString(coordinates[0]), Double.toString(coordinates[1]), deviceId, deviceEmail);
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(Void v) {
}
}
//image preview dialog and its functionality
private void imagePreviewDialog(){
//setting the bitmap
Bitmap bmp = BitmapFactory.decodeFile(mediaFile.toString());
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Image Preview");
builder.setCancelable(false);
LayoutInflater inflater = getActivity().getLayoutInflater();
ViewGroup vg = (ViewGroup)inflater.inflate(R.layout.sanp_preview_layout, null);
ImageView image = (ImageView) vg.findViewById(R.id.imageView);
image.setImageBitmap(rotateBitmap(bmp));
builder.setView(vg);
//buttons
builder.setPositiveButton("Upload",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
if(checkInternetConnection.haveNetworkConnection(sContext)){
//upload the image
uploadImage();
//save image metadata
new SaveMetadataTask().execute();
}else{
Toast.makeText(sContext, "Error! No internet connection detected. Image will be uploaded on an active internet connection", Toast.LENGTH_LONG).show();
new SaveMetadataTask().execute();
}
}
});
builder.setNegativeButton("Discard",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
discardImage(mediaFile.toString());
dialog.dismiss();
}
});
builder.show();
}
private Bitmap rotateBitmap(Bitmap image){
int width=image.getHeight();
int height=image.getWidth();
Bitmap srcBitmap=Bitmap.createBitmap(width, height, image.getConfig());
for (int y=width-1;y>=0;y--)
for(int x=0;x<height;x++)
srcBitmap.setPixel(width-y-1, x,image.getPixel(x, y));
return srcBitmap;
}
//device email
private String getDeviceEmail(){
AccountManager accountManager = AccountManager.get(sContext);
Account[] account = accountManager.getAccountsByType("com.google");
//device email
for(Account accLoop : account){
deviceEmail = accLoop.name;
}
return deviceEmail;
}
//upload image to the server
private void uploadImage(){
//save metadata
//call upload service
Intent intent = new Intent(sContext, HttpUploader.class);
Bundle loc = new Bundle();
loc.putDoubleArray("ss", coordinates);
intent.putExtra("url", PHOTO_UPLOAD);
intent.putExtra("paths", mediaFile.toString());
intent.putExtra("deviceid", deviceId);
intent.putExtra("deviceemail", getDeviceEmail());
intent.putExtra("posttext", "This is for testing");
intent.putExtra("filename", file_name_without_extension);
intent.putExtra("geo", loc);
sContext.startService(intent);
Toast.makeText(getActivity(), "Your image is being uploaded", Toast.LENGTH_LONG).show();
}
//discard image when the discard button is pressed
private void discardImage(String imagePath){
File file = new File(imagePath);
try{
file.delete();
}catch(Exception e){
Log.e("IMAGE_DELETION_ERROR", e.toString());
}
}
@Override
public void onTaskCompleted(boolean status, String message) {
// TODO Auto-generated method stub
Log.e("onTaskCompleted", "success" + status);
if (message == "tumb UP success") {
thumbUpBut.setSelected(true);
thumbDownBut.setSelected(false);
Log.e("tumb", "tumb");
} else if (message == "tumb DOWN success") {
thumbDownBut.setSelected(true);
thumbUpBut.setSelected(false);
Log.e("tumb", "tumb");
}
}
//listener for fetching main objects
@Override
public void onFeedCompleted(ArrayList<Posts> postArray, Multimap<String, Object> multiMap) {
// TODO Auto-generated method stub
numberOfPages = postArray.size();
adapter = new Slider(getActivity(), postArray, getContext());
viewPager.setAdapter(adapter);
// displaying selected image first
viewPager.setCurrentItem(postArray.size());
//saving the keyset
Set<String> keys = multiMap.keySet();
sections = new ArrayList<String>();
//sorting the categories and creating the category list
for(String key:keys){
//getting category list
if(!sections.contains(keys)){
sections.add(key);
}
//sorting categories
if(key.equals("Place")){
places.add((Place) multiMap.get(key));
}else if(key.equals("Events")){
events.add((Happenings) multiMap.get(key));
}else if(key.equals("General")){
general.add((General) multiMap.get(key));
}
}
}
//adding the pages to the adaptor dynamically
public void addPagesDynamically(){
}
}
//create the parent directory
private void createParentDiectory(){
File dir = new File(Environment.getExternalStorageDirectory() + "/Android/data/asia.ceynet.realsnap");
if(!(dir.exists() && dir.isDirectory())) {
dir.mkdirs();
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case R.id.action_post:
openPost();
return true;
case R.id.action_settings:
// openSettings();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void openPost() {
/*
Intent i = new Intent(getApplicationContext(), PhotoActivity.class);
startActivity(i);
*/
}
public static void thumb(String type) {
SectionFragment d = new SectionFragment();
PostThumb task = new PostThumb(type, d);
task.execute("xxxxxxxxxxxxxxxxxxxxxxxxxxxx");
}
//broadcast receiver for picture upload
public class MyWebRequestReceiver extends BroadcastReceiver {
public static final String PROCESS_RESPONSE = "asia.ceynet.intent.action.PROCESS_RESPONSE";
@Override
public void onReceive(Context context, Intent intent) {
//String responseString = intent.getStringExtra(HttpUploader.RESPONSE_STRING);
String reponseMessage = intent.getStringExtra(HttpUploader.RESPONSE_MESSAGE);
String responseStatus = intent.getStringExtra(HttpUploader.RESPONSE_STATUS);
String file_to_be_deleted = intent.getStringExtra(HttpUploader.FILE_NAME_WITHOUT_EXTENSION);
Toast.makeText(getApplicationContext(), reponseMessage + " - " + file_to_be_deleted + ".jpg", Toast.LENGTH_LONG).show();
//if uploaded successfully delete or image and metadata
if(responseStatus.equals("true")){
File temp_image_dir = new File(Environment.getExternalStorageDirectory() + "/Android/data/asia.ceynet.realsnap/temp_img/" + file_to_be_deleted + ".jpg");
File metadata_file = new File(Environment.getExternalStorageDirectory() + "/Android/data/asia.ceynet.realsnap/temp_img/" + file_to_be_deleted + ".ser");
try{
temp_image_dir.delete();
metadata_file.delete();
}catch(Exception e){
Log.e("IMAGE_DELETION_ERROR", e.toString());
}
}
}
}
最佳答案
当您完成提取异步数据时，请向适配器提供新数据并在该适配器实例上调用.notifyDataSetChanged（），框架将自行更新页面并进行计数。
如果您希望获得更详细的说明，请发布FragmentPagerAdapter实现。
关于java - FragmentPagerAdapter动态选项卡和页数，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24887083/