[android-developers] TabActivity with multiple nested acitivities based on Button Click

[youssef]

The problem I face is how to navigate through tab activity with nested
activities based on Button click android.

I have 3 tabs Dashboard, Vehicle search, and Location search. When I
press the location search tab I get a Edit text(to enter the zip code)
and  go button(when I press it I should get the locations in 100 miles
of zip code in different page called Location Search Results page)

My specific problem is the app crashes when I press go button and
before I get the locations

I have MainActivity class which extends the TabActivity and define all
the tabs

public class MainActivity extends TabActivity
{
      public TabHost tabHost;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tabHost = (TabHost) findViewById(android.R.id.tabhost);
        TabHost.TabSpec spec;
        Intent intent;

        intent = new Intent().setClass(this, DashBoard.class);
        spec =
tabHost.newTabSpec("dashboard").setIndicator("DashBoard").setContent(intent);
        tabHost.addTab(spec);

        intent = new Intent().setClass(this, VehicleSearch.class);
        spec =
tabHost.newTabSpec("vehicleSearch").setIndicator("VehicleSearch").setContent(intent);
        tabHost.addTab(spec);

        intent = new Intent().setClass(this, BranchSearch.class);
        spec =
tabHost.newTabSpec("branchSearch").setIndicator("BranchSearch").setContent(intent);
        tabHost.addTab(spec);

        tabHost.setCurrentTab(3);


}

I also have the BranchSearchHelper class which extends ActivityGroup

public class BranchSearchHelper extends ActivityGroup
{
      public static BranchSearchHelper branchSearch;
      private ArrayList<View> history;
      @Override
    public void onCreate(Bundle savedInstanceState)
      {
        super.onCreate(savedInstanceState);
        branchSearch = this;
        this.history = new ArrayList<View>();


        View view =
getLocalActivityManager().startActivity("BranchSearch", new
Intent(this,BranchSearch.class)
                  .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView();

        replaceView(view);

      }

      public void replaceView(View v)
      {
                           // Adds the old one to history
                    history.add(v);
                            // Changes this Groups View to the new
View.
                    setContentView(v);
      }

       public void back()
       {
                     if(history.size() > 0) {
                         history.remove(history.size()-1);
 
setContentView(history.get(history.size()-1));
                     }
                     else
                     {
                         finish();
                     }
}

                @Override
                public void onBackPressed()
                {

                  BranchSearchHelper.branchSearch.back();
                     return;
                 }


}

The class BranchSearch extends Activity

public class BranchSearch extends Activity implements OnClickListener
{

      public void onCreate(Bundle savedInstanceState)
      {
              super.onCreate(savedInstanceState);
              setContentView(R.layout.branchsearch);
              Button locSearch = (Button)
findViewById(R.id.btnlocSearch);
              locSearch.setOnClickListener(this);


          }

       public void onClick(View v)
      {
                  // TODO Auto-generated method stub

                  EditText editText = (EditText)
findViewById(R.id.lsearch);

                  Bundle bundle = new Bundle();
                  bundle.putString("zipCode",
editText.getText().toString() );

                  Intent i = new Intent(getApplicationContext(),
LocationSearchResults.class);
                  i.putExtras(bundle);
                  i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);


                 View view =
BranchSearchHelper.branchSearch.getLocalActivityManager().startActivity("Locations
Results",i).getDecorView();

                  BranchSearchHelper.branchSearch.replaceView(view);




            }


}

I always get an javaNUllPointerexception the exception throws at
View view =
BranchSearchHelper.branchSearch.getLocalActivityManager().startActivity("Locations
Results",i).getDecorView();
because branchSearch is null

 so can you please tell me how I can keep the track of tabs and show
the all the location results when I press the go button without
crashing the application. ( what parts of code should I change)

There is a class called LocationSearchResults which handles the
displaying of all location search results.

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