我创建了一个具有viewpager的fragmentactivity（MainActivity），因为我有3个listfragments。当在列表片段之一（AllPatient）中按下listitem时，会打开另一个片段活动（PrescAct），其中包含一个包含3个片段的viewpager。
我的问题是，当按下AllPatient列表项时，patient_id将传递给PrescAct，PrescAct又将该值传递给片段DocPresc。我在DocPresc.class中pid = b.getString("TAG_PATIENT_ID1");获得Null Pointer Exception。
请建议，我在这个问题上坚持了很长时间。
以下是代码。
MainActivity FragmentActivity：
public class MainActivity extends FragmentActivity {
/** Called when the activity is first created. */
static AppSectionsPagerAdapter mAppSectionsPagerAdapter;
ViewPager mViewPager;
SearchView mSearchView;
MenuItem menuSearch;
Boolean flag = false;
String pid;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setupActionBar();
//getActionBar().setTitle("All Patients");
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOffscreenPageLimit(3);
mViewPager.setCurrentItem(0);
mViewPager.setOnPageChangeListener(new OnPageChangeListener()
{
public void onPageSelected(int position)
{
//mAppSectionsPagerAdapter.getItemPosition(getFragmentManager().findFragmentById(position));
//getActionBar().setTitle(mAppSectionsPagerAdapter.getPageTitle(position));
// getActionBar().setTitle(getTitle(position));
//mAppSectionsPagerAdapter.notifyDataSetChanged();
if(position==0){
getActionBar().setTitle("All Patients");
flag = true;
// menuSearch.setVisible(true);
//menuSearch.
invalidateOptionsMenu();
}
if(position==1){
getActionBar().setTitle("All Doctors");
flag=false;
// menuSearch.setVisible(false);
invalidateOptionsMenu();
}
else
getActionBar().setTitle("All Nurses");
invalidateOptionsMenu();
}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
{
}
public void onPageScrollStateChanged(int state)
{
if (state == ViewPager.SCROLL_STATE_DRAGGING)
{
}
if (state == ViewPager.SCROLL_STATE_IDLE)
{
}
}
});
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new AllPatient();
case 1:
//Intent intent = new Intent(MainActivity.this,abc.class);
return new AllDoctors();
case 2:
return new AllNurses();
}
return null;
}
@Override
public int getCount() {
return 3;
}
}
}
AllPatient ListFragment：
public class AllPatient extends ListFragment {
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList = new ArrayList<HashMap<String,String>>();
// url to get all products list
private static String url_all_patients = "http://192.168.44.208/get_all_patients.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PATIENT_ID = "patient_id";
private static final String TAG_PATIENT_NAME = "patient_name";
JSONArray products = null;
Context ctx;
String pid;
EditText inputSearch;
ListAdapter adapter;
ListView lv;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.patient_list, container, false);
//ListView lv;
// lv = (ListView)view.findViewById(android.R.id.list);
//ListView v = getListView();
getActivity().getActionBar().setTitle("All Patients");
new LoadAllPatients().execute();
return view;
}
@Override
public void onListItemClick(ListView lv, View v, int position, long id) {
// TODO Auto-generated method stub
onAttach(getActivity());
//lv.setAdapter(adapter);
String id1 = ((TextView) v.findViewById(R.id.pid)).getText().toString();
System.out.println("all patient"+id1);
Bundle bundle = new Bundle();
bundle.putString("TAG_PATIENT_ID",id1 );
System.out.println("bundle"+id1);
Intent i = new Intent(getActivity(),PrescAct.class);
i.putExtras(bundle);
startActivity(i);
//passData(date);
Toast.makeText(
getActivity(),
getListView().getItemAtPosition(position).toString(),
Toast.LENGTH_LONG).show();
}
class LoadAllPatients extends AsyncTask<String, String, String> {
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_patients, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Patients: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PATIENT_ID).toUpperCase();
String name = c.getString(TAG_PATIENT_NAME).toUpperCase();
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PATIENT_ID, id);
map.put(TAG_PATIENT_NAME, name);
// adding HashList to ArrayList
productsList.add(map);
Collections.sort(productsList, new Comparator<Map<String, String>>() {
public int compare(Map<String, String> o1, Map<String, String> o2) {
String name1 = o1.get("patient_name");
String name2 = o2.get("patient_name");
if (name1 == null) return -1;
return name1.compareTo(name2);
}
});
}
} else {
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
// pDialog.dismiss();
// updating UI from Background Thread
getActivity().runOnUiThread(new Runnable() {
public void run() {
ListAdapter adapter = new SimpleAdapter(
getActivity(), productsList,
R.layout.list_item1, new String[] { TAG_PATIENT_ID,
TAG_PATIENT_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
//setListAdapter(adapter);
setListAdapter(adapter);
inputSearch = (EditText)getView().findViewById(R.id.inputSearch);
inputSearch.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
// When user changed the Text
//ListView lv = getListView();
((SimpleAdapter) getListAdapter()).getFilter().filter(cs);
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
});
}
});
}
}
这是PrescAct FragmentActivity：
public class PrescAct extends FragmentActivity {
/** Called when the activity is first created. */
static AppSectionsPagerAdapter mAppSectionsPagerAdapter;
ViewPager mViewPager;
SearchView mSearchView;
MenuItem menuSearch;
Boolean flag = false;
String pid;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.prescact);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setupActionBar();
//getActionBar().setTitle("All Patients");
// Getting value of pid from all patient
Intent i = getIntent();
Bundle extras = i.getExtras();
pid = extras.getString("TAG_PATIENT_ID");
System.out.println("Pid in prescact"+pid);
// Bundle bundle = new Bundle();
/* bundle.putString("TAG_PATIENT_ID",pid);
Intent m = new Intent(PrescAct.this,DocPresc1.class);
m.putExtras(bundle);*/
//Passing pid value to the list fragment
Bundle b = new Bundle();
b.putString("TAG_PATIENT_ID1",pid);
Fragment f = new DocPresc1();
f.setArguments(b);
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager1);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOffscreenPageLimit(3);
mViewPager.setCurrentItem(2);
mViewPager.setOnPageChangeListener(new OnPageChangeListener()
{
public void onPageSelected(int position)
{
//mAppSectionsPagerAdapter.getItemPosition(getFragmentManager().findFragmentById(position));
//getActionBar().setTitle(mAppSectionsPagerAdapter.getPageTitle(position));
// getActionBar().setTitle(getTitle(position));
//mAppSectionsPagerAdapter.notifyDataSetChanged();
if(position==0){
getActionBar().setTitle("Prescription1");
flag = true;
// menuSearch.setVisible(true);
//menuSearch.
invalidateOptionsMenu();
}
if(position==1){
getActionBar().setTitle("Prescription2");
flag=false;
// menuSearch.setVisible(false);
invalidateOptionsMenu();
}
else
System.out.println("today fragment");
getActionBar().setTitle("Today's Prescription");
invalidateOptionsMenu();
}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
{
}
public void onPageScrollStateChanged(int state)
{
if (state == ViewPager.SCROLL_STATE_DRAGGING)
{
}
if (state == ViewPager.SCROLL_STATE_IDLE)
{
}
}
});
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new AllPatient();
case 1:
//Intent intent = new Intent(MainActivity.this,abc.class);
return new AllDoctors();
case 2:
System.out.println("today fragment called");
return new DocPresc1();
}
return null;
}
@Override
public int getCount() {
return 3;
}
}
这是DocPresc片段：
public class DocPresc1 extends ListFragment {
//public static Context ctx;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList = new ArrayList<HashMap<String,String>>();
String pid;
JSONArray products = null;
EditText ailm,date,comment;
Button delete;
ListAdapter adapter;
JSONParser jsonParser = new JSONParser();
// single product url
private static final String url_patient_presc = "http://192.168.44.208/get_prescription.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
// private static final String TAG_PATIENT_ID = "patient_id";
private static final String TAG_AIL = "ailment";
private static final String[] TAG_MED = {"medicine_id","medicine_id2"};
private static final String TAG_D1 = "qty1";
private static final String TAG_D2 = "qty2";
private static final String TAG_D3 = "qty3";
private static final String TAG_DATE = "prescription_date";
private static final String TAG_COM = "comment";
private static final String TAG_PRESCRIPTION = "prescription_id";
//private static final String TAG_DID = "dosage_id";
// private static final String TAG_MED1_D1 = "m1dosage";
private static final String[] TAG_MED_D = {"m1dosage","m2dosage"};
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.docpresc1, container, false);
// setContentView(R.layout.docpresc);
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads().detectDiskWrites().detectNetwork() // StrictMode is most commonly used to catch accidental disk or network access on the application's main thread
.penaltyLog().build());
// Intent i = getIntent();
//Intent i = new Intent(getApplicationContext);//,PrescAct.class);
/* Bundle extras = i.getExtras();
pid = extras.getString("TAG_PATIENT_ID");*/
Bundle b = getArguments();
pid = b.getString("TAG_PATIENT_ID1");
// System.out.println("Docpresc"+pid);
// pid=getArguments().getString("TAG_PATIENT_ID1");
System.out.println("Docpresc"+pid);
// return inflater.inflate(R.layout.fragment, container, false);
ailm = (EditText)getView().findViewById(R.id.ailment1);
date = (EditText)getView().findViewById(R.id.date1);
comment = (EditText)getView().findViewById(R.id.comment1);
// if (savedInstanceState == null) {
new LoadPrescriptions().execute();
// }
return view;
// return inflater.inflate(R.layout.fragment, container, false);
}
class LoadPrescriptions extends AsyncTask<String, String, String> {
protected String doInBackground(String... args) {
// Building Parameters
getActivity().runOnUiThread(new Runnable() {
public void run() {
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
//pid=getArguments().getString("TAG_PATIENT_ID1");
// System.out.println("Docpresc"+pid);
// getting JSON string from URL
params.add(new BasicNameValuePair("patient_id",pid));//search1.getText().toString()));
System.out.println("database"+pid);
JSONObject json = jParser.makeHttpRequest(url_patient_presc, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Patients: ", json.toString());
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
//-----------------------------------
/*JSONObject product = products.getJSONObject(0);
ailm = (EditText)findViewById(R.id.ailment1);
ailm.setText(product.getString(TAG_AIL));*/
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
for(int m =0;m<2;m++){
String medicine = c.getString(TAG_MED[m]).toUpperCase();
String prescription = c.getString(TAG_PRESCRIPTION);
//String medicine[] = ((String) c.get(TAG_MED[i])).toUpperCase();
// String qty1 = c.getString(TAG_D1).toUpperCase();
// String qty2 = c.getString(TAG_D2).toUpperCase();
// String qty3 = c.getString(TAG_D3).toUpperCase();
String dosage = c.getString(TAG_MED_D[m]);
// String dsg_id = c.getString(TAG_DID).toUpperCase();
//String ail = c.getString(TAG_AIL).toUpperCase();
//getting 3 bytes from dosage1
String do1 = Character.toString(dosage.charAt(0));
String do2 = Character.toString(dosage.charAt(1));
String do3 = Character.toString(dosage.charAt(2));
//char do2 = dosage1.charAt(1);
//char do3 = dosage1.charAt(2);
ailm.setText(c.getString(TAG_AIL));
date.setText(c.getString(TAG_DATE));
comment.setText(c.getString(TAG_COM));
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
System.out.println("medicine"+medicine+m);
if(medicine.equals("NULL")==false){
System.out.println("medicine in if"+medicine+m);
map.put(TAG_MED[i], medicine);
map.put(TAG_MED_D[i],dosage);
map.put(TAG_D1,do1);
map.put(TAG_D2,do2);
map.put(TAG_D3,do3);
map.put(TAG_PRESCRIPTION,prescription);
// map.put(TAG_DID,dsg_id);
//if(map.containsValue(null)==false)
// adding HashList to ArrayList
productsList.add(map);
//if (productsList.get(m).containsValue(null))
// productsList.remove(m);
System.out.println("productsList"+m+productsList);
}
}
}
} else {
}
} catch (JSONException e) {
e.printStackTrace();
}
}
});
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
// pDialog.dismiss();
// updating UI from Background Thread
getActivity().runOnUiThread(new Runnable() {
public void run() {
//ListAdapter
adapter = new SimpleAdapter(
getActivity(), productsList,
R.layout.list_item2, new String[] {
TAG_MED[0],TAG_D1,TAG_D2,TAG_D3,TAG_MED_D[0],TAG_PRESCRIPTION},
// TAG_MED,TAG_MED1_D1},
new int[] {R.id.med,R.id.d1,R.id.d2,R.id.d3,R.id.dos1,R.id.pres});
// new int[] {R.id.med,R.id.dos1});
// updating listview
//setListAdapter(adapter);
setListAdapter(adapter);
}
});
}
}
这是堆栈跟踪：
06-20 12:44:34.767: E/AndroidRuntime(9394): FATAL EXCEPTION: main
06-20 12:44:34.767: E/AndroidRuntime(9394): java.lang.NullPointerException
06-20 12:44:34.767: E/AndroidRuntime(9394): at com.example.actionbar.DocPresc1.onCreateView(DocPresc1.java:104)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:461)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.view.ViewPager.populate(ViewPager.java:1011)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.view.ViewPager.populate(ViewPager.java:880)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1374)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.View.measure(View.java:15479)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:617)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:399)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.View.measure(View.java:15479)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4828)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.View.measure(View.java:15479)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.LinearLayout.measureVertical(LinearLayout.java:833)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.View.measure(View.java:15479)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4828)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
06-20 12:44:34.767: E/AndroidRuntime(9394): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2359)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.View.measure(View.java:15479)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1968)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1214)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1387)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4464)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.Choreographer.doFrame(Choreographer.java:525)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.os.Handler.handleCallback(Handler.java:615)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.os.Handler.dispatchMessage(Handler.java:92)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.os.Looper.loop(Looper.java:137)
06-20 12:44:34.767: E/AndroidRuntime(9394): at android.app.ActivityThread.main(ActivityThread.java:4895)
06-20 12:44:34.767: E/AndroidRuntime(9394): at java.lang.reflect.Method.invokeNative(Native Method)
06-20 12:44:34.767: E/AndroidRuntime(9394): at java.lang.reflect.Method.invoke(Method.java:511)
06-20 12:44:34.767: E/AndroidRuntime(9394): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
06-20 12:44:34.767: E/AndroidRuntime(9394): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
06-20 12:44:34.767: E/AndroidRuntime(9394): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
ailm = (EditText)getView().findViewById(R.id.ailment1);
date = (EditText)getView().findViewById(R.id.date1);
comment = (EditText)getView().findViewById(R.id.comment1);
return view;
Fragment.getView（）返回您在onCreateView中返回的内容，因此在onCreateView返回之前无法使用。改变这种方式
ailm = (EditText)view.findViewById(R.id.ailment1);
date = (EditText)view.findViewById(R.id.date1);
comment = (EditText)view.findViewById(R.id.comment1);
来自Android documentation：
Get the root view for the fragment's layout (the one returned by onCreateView(LayoutInflater, ViewGroup, Bundle)), if provided.
Returns
The fragment's root view, or null if it has no layout.