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Android 2.1 NullPointerException with TabWidgets

I have a problem that I could not figure out, and this only happens on devices running <2.1. It works fine on Android 2.2. I have a synchronous task that displays a download dialog when it loads all tabs. Here is the code for TabActivity:

public class OppTabsView extends TabActivity { Dialog dialog; String errorText; boolean save; final int OPP_SAVE = 0; public static boolean edited; public void onCreate(Bundle icicle) { try { super.onCreate(icicle); new DoInBackground().execute(); } catch (Exception e) { Toast.makeText(this, "Error occured. Please try again later.", Toast.LENGTH_SHORT).show(); } } @Override protected void onResume() { super.onResume(); } @Override protected void onStop() { super.onStop(); } @Override protected void onPause() { super.onPause(); } public boolean onCreateOptionsMenu(Menu menu) { menu.add(0, OPP_SAVE, 0, "Test"); return true; } public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case OPP_SAVE: save = true; new DoInBackground().execute(); return true; } return false; } public void LoadOpp() { handler.sendEmptyMessage(0); } public void SaveOpp() { DoStuff(); } public void LoadLayout() { setContentView(R.layout.view_opptabs); /* TabHost will have Tabs */ TabHost tabHost = (TabHost) findViewById(android.R.id.tabhost); /* * TabSpec used to create a new tab. By using TabSpec only we can able * to setContent to the tab. By using TabSpec setIndicator() we can set * name to tab. */ /* tid1 is firstTabSpec Id. Its used to access outside. */ TabSpec firstTabSpec = tabHost.newTabSpec("tid1"); TabSpec secondTabSpec = tabHost.newTabSpec("tid1"); TabSpec thirdTabSpec = tabHost.newTabSpec("tid1"); /* TabSpec setIndicator() is used to set name for the tab. */ /* TabSpec setContent() is used to set content for a particular tab. */ firstTabSpec.setIndicator("General", getResources().getDrawable(R.drawable.tab_moneybag)) .setContent(new Intent(this, OppTabGeneral.class)); secondTabSpec.setIndicator("Details", getResources().getDrawable(R.drawable.tab_papers)).setContent( new Intent(this, OppTabDetails.class)); thirdTabSpec.setIndicator("Contact", getResources().getDrawable(R.drawable.tab_contact)).setContent( new Intent(this, OppTabContact.class)); /* Add tabSpec to the TabHost to display. */ tabHost.addTab(firstTabSpec); tabHost.addTab(secondTabSpec); tabHost.addTab(thirdTabSpec); } private void do_update() { if (save) { SaveOpp(); } else { LoadOpp(); } } Handler handler = new Handler() { public void handleMessage(Message msg) { LoadLayout(); } }; private class DoInBackground extends AsyncTask<Void, Void, Void> implements DialogInterface.OnCancelListener { protected void onPreExecute() { String verb = "Connecting"; if (save) { verb = "Saving"; } dialog = ProgressDialog.show(OppTabsView.this, "", verb + ". Please Wait...", true, true, this); } protected Void doInBackground(Void... v) { do_update(); return null; } protected void onPostExecute(Void v) { dialog.dismiss(); } public void onCancel(DialogInterface dialog) { cancel(true); dialog.dismiss(); finish(); } } }

Here is the stack trace from the error:

 java.lang.NullPointerException at android.widget.TabWidget.dispatchDraw(TabWidget.java:206) at android.view.ViewGroup.drawChild(ViewGroup.java:1529) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) at android.view.ViewGroup.drawChild(ViewGroup.java:1529) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) at android.view.ViewGroup.drawChild(ViewGroup.java:1529) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) at android.view.View.draw(View.java:6538) at android.widget.FrameLayout.draw(FrameLayout.java:352) at android.view.ViewGroup.drawChild(ViewGroup.java:1531) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) at android.view.ViewGroup.drawChild(ViewGroup.java:1529) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) at android.view.View.draw(View.java:6538) at android.widget.FrameLayout.draw(FrameLayout.java:352) at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1830) at android.view.ViewRoot.draw(ViewRoot.java:1349) at android.view.ViewRoot.performTraversals(ViewRoot.java:1114) at android.view.ViewRoot.handleMessage(ViewRoot.java:1633) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:4363) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:521) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) at dalvik.system.NativeStart.main(Native Method)

I tried to get through it, but the error seems to be coming from outside, not on a specific line. Any help is appreciated.

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4 answers
 TabSpec firstTabSpec = tabHost.newTabSpec("tid1"); TabSpec secondTabSpec = tabHost.newTabSpec("tid1"); TabSpec thirdTabSpec = tabHost.newTabSpec("tid1");

Can I use the same tag for multiple TabSpec? I would try installing them correctly and see if it fixes it.

EDIT: OK, so my suggestion didn't fix it, but it makes sense to have unique tags.

Try this to see if this helps. Add a parameter to set the currently selected tab at the end of your LoadLayout () method, as shown below (see last line) ...

 /* Add tabSpec to the TabHost to display. */ tabHost.addTab(firstTabSpec); tabHost.addTab(secondTabSpec); tabHost.addTab(thirdTabSpec); tabHost.setCurrentTab(0); // <== Add this

EDIT2: I found the source of TabWidget.java and line 206 (where the NullPointerException is thrown) ...

mBottomLeftStrip.setState(selectedChild.getDrawableState());

... There are three possible reasons for the exception that I see.

  • mBottonLeftStrip is null (unlikely)
  • selectedCHild is null (TabWidget should by default be a child of 0, and using tabHost.setCurrentTab () would ensure compliance anyway)
  • The result of selectedChild.getDrawableState() is null

The latter seems like a likely cause, but I'm not sure what might make it return null.

Try Google for “TabWidget.java source” - the second result on the grepcode.com page with line numbers, and you can see what it is trying to do at the exception point.

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There was the same problem with tabs populated from AsyncTask on 1.6 and 2.1. It seems that earlier versions do not like TabHost without any tabs. To solve this problem, I do not use TabActivity and create TabHost with all my hierarchy manually in the onPostExecute AsyncTask function.

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A simple solution is to set the tabWidget visibility in the expired in your layout

 <TabWidget android:id="@android:id/tabs" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="0" android:visibility="gone" />

Then, once you have defined your tabs, you can make it visible again:

 // Add tab content (here a fragment class) tabHost.addTab( tabHost.newTabSpec("tag1").setIndicator("Title"), contentFragment.class, null); // Set tabWidget visible again tabWidget.setVisibility(View.VISIBLE);
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Inspired by one of the related TabHost answers:

 public class FixedTabHost extends FragmentTabHost { public FixedTabHost(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void dispatchDraw(Canvas canvas) { try { super.dispatchDraw(canvas); } catch (Exception ignored) {} } }

Worked for me.

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Source: https://habr.com/ru/post/1340098/

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