-2
我正在開發一個應用程序，我想檢查互聯網連接是否存在，然後它會執行任務，否則它會顯示錯誤消息，如沒有互聯網連接there.In此應用程序我我使用2個選項卡。我寫了一個代碼來檢查互聯網連接，但每當沒有連接時，我的應用程序崩潰。如何檢查Fragement選項卡中的互聯網連接
代碼主要活動：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (!isNetworkAvailable()) {
Toast.makeText(getApplicationContext(),
"Internet Connection is Not Available", Toast.LENGTH_LONG).show();
finish();
} else {
if (getIntent().getExtras() != null) {
for (String key : getIntent().getExtras().keySet()) {
String value = getIntent().getExtras().getString(key);
if (key.equals("Tab_Notification") && value.equals("True")) {
Intent intent = new Intent(this, Tab_Notification.class);
intent.putExtra("value", value);
startActivity(intent);
finish();
}
}
}
subscribeToPushService();
final Handler mHandler = new Handler();
final Runnable mUpdateResults = new Runnable() {
public void run() {
AnimateandSlideShow();
}
};
int delay = 1000; // delay for 1 sec.
int period = 15000; // repeat every 4 sec.
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
public void run() {
mHandler.post(mUpdateResults);
}
}, delay, period);
SharedPreferences sharedpreferences = getSharedPreferences(SignIn.MyPREFERENCES, Context.MODE_PRIVATE);
final String e = sharedpreferences.getString(SignIn.email, "");
toolbar = (Toolbar) findViewById(R.id.toolbar1);
tabLayout = (TabLayout) findViewById(R.id.tab_layout1);
viewPager = (ViewPager) findViewById(R.id.pager1);
i = (ImageView) findViewById(R.id.pinButton);
i.setOnClickListener(this);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);
tabLayout.addTab(tabLayout.newTab().setText("Super Market"));
tabLayout.addTab(tabLayout.newTab().setText("Shopping"));
tabLayout.addTab(tabLayout.newTab().setText("FOOD"));
tabLayout.addTab(tabLayout.newTab().setText("Cosmetics"));
tabLayout.addTab(tabLayout.newTab().setText("Medical"));
tabLayout.addTab(tabLayout.newTab().setText("Hotels"));
tabLayout.addTab(tabLayout.newTab().setText("Jewellery"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
fragmentAdapter = new FragmentAdapterClass(getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(fragmentAdapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab LayoutTab) {
viewPager.setCurrentItem(LayoutTab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab LayoutTab) {
}
@Override
public void onTabReselected(TabLayout.Tab LayoutTab) {
}
});
}
}
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager
.getActiveNetworkInfo();
return activeNetworkInfo != null;
}
TAB1代碼：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.activity_tab_1, container, false);
recyclerView = (RecyclerView) v.findViewById(R.id.recyclerview);
recyclerView.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
mSwipeRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.swifeRefresh);
mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
getData();
upcomingJobs.clear();
upcomingJobs.addAll(upcomingJobs);
// fire the event
adapter.notifyDataSetChanged();
// uAdapter.notifyDataSetChanged();
}
});
//Make call to AsyncTask
getData();
return v;
}
private void getData() {
class GetData extends AsyncTask<Void, Void, String> {
ProgressDialog progressDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
// progressDialog = ProgressDialog.show(getContext(), "Fetching Data", "Please wait...",false,false);
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
// progressDialog.dismiss();
parseJSON(s);
mSwipeRefreshLayout.setRefreshing(false);
}
@Override
protected String doInBackground(Void... params) {
BufferedReader bufferedReader = null;
try {
URL url = new URL(Config.GET_URL);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String json;
while ((json = bufferedReader.readLine()) != null) {
sb.append(json + "\n");
}
return sb.toString().trim();
} catch (Exception e) {
return null;
}
}
}
GetData gd = new GetData();
gd.execute();
}
public void showData() {
adapter = new CardAdapter(Config.offer, Config.offerprice, Config.bitmaps, Config.price, Config.urls);
recyclerView.setAdapter(adapter);
recyclerView.addOnItemTouchListener(new RecyclerItemClickListener(getContext(), new RecyclerItemClickListener.OnItemClickListener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(getContext(), "Card at " + position + " is clicked", Toast.LENGTH_SHORT).show();
}
}));
}
private void parseJSON(String json) {
try {
JSONObject jsonObject = new JSONObject(json);
JSONArray array = jsonObject.getJSONArray(Config.TAG_JSON_ARRAY);
config = new Config(array.length());
for (int i = 0; i < array.length(); i++) {
JSONObject j = array.getJSONObject(i);
Config.offer[i] = getoffer(j);
Config.urls[i] = geturl(j);
Config.offerprice[i] = getofferprice(j);
Config.price[i] = getprice(j);
Config.urls[i] = geturl(j);
}
} catch (JSONException e) {
e.printStackTrace();
}
GetBitmap gb = new GetBitmap(getContext(), this, Config.urls);
gb.execute();
}
private String getoffer(JSONObject j) {
String name = null;
try {
name = j.getString(Config.TAG_Offer);
} catch (JSONException e) {
e.printStackTrace();
}
return name;
}
private String getofferprice(JSONObject j) {
String name = null;
try {
name = j.getString(Config.TAG_Offerprice);
} catch (JSONException e) {
e.printStackTrace();
}
return name;
}
private String getprice(JSONObject j) {
String name = null;
try {
name = j.getString(Config.TAG_price);
} catch (JSONException e) {
e.printStackTrace();
}
return name;
}
private String geturl(JSONObject j) {
String url = null;
try {
url = j.getString(Config.TAG_IMAGE_URL);
} catch (JSONException e) {
e.printStackTrace();
}
return url;
}
的logcat：
FATAL EXCEPTION: main
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:156)
at org.json.JSONObject.<init>(JSONObject.java:173)
at com.zaps.myrewards.Tab_1_Activity.parseJSON(Tab_1_Activity.java:144)
at com.zaps.myrewards.Tab_1_Activity.access$300(Tab_1_Activity.java:31)
at com.zaps.myrewards.Tab_1_Activity$1GetData.onPostExecute(Tab_1_Activity.java:92)
at com.zaps.myrewards.Tab_1_Activity$1GetData.onPostExecute(Tab_1_Activity.java:78)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5938)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
請發佈您的logcat。 – adalPaRi
請檢查我的更新代碼 – user