Activities and sub activities

Question

My Application has 5 different activities ( name them as A,B,C,D,E ) and there is a menu (made by buttons on bottom of the screen), to switch between A,B...E

when I am displaying A, there are some button by which the user goes on another activity A1 on top of A, then from there he goes into A12, so my activity stack is something like A>A1>A12, now the user click on menu button for B, then he goes on B1 from there . (Stack would be like A>A1>A12>B>B1) now if user press the button to switch back to A, so it should display A12, as it is on top of A.

how do I manage this scanario? I have no hint at all

Answer 1

I suggest you should create a tabHost contains all 5 Activity A, B, C, D, E.

After initialize tabHost, let hide this tab bar by calling:

tabHost.getTabWidget.setVisibility(View.GONE);

And you should switch between each Activity like this:

public boolean onOptionsItemSelected( MenuItem item ) 
{
switch (item.getItemId()) 
{
    case R.id.menu_item_A:
        tabHost.setCurrentTab(0);
        return true;

    case R.id.menu_item_B:
        tabHost.setCurrentTab(1);
        return true;

    case R.id.menu_item_C:
        tabHost.setCurrentTab(2);
        return true;

    case R.id.menu_item_D:
        tabHost.setCurrentTab(3);
        return true;

    case R.id.menu_item_E:
        tabHost.setCurrentTab(4);
        return true;

    return false;
}

So, when you are in A1 -> A2, and switch to Activity B, and use menu to switch back A, you're still in A2.

Hope it can help you.

Answer 2

Instead of buttons at bottom of the screen, use TabHost and ActivityGroup to display multiple activities under the selected tab.

<TabHost
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@android:id/tabhost"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">

  <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <FrameLayout
      android:id="@android:id/tabcontent"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_weight="1" />

    <TabWidget
      android:id="@android:id/tabs"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_weight="0" />

  </LinearLayout>

</TabHost>

Main activity:

/**
 * Activity that displays the main tabs and manages separate activity for the
 * selected tab.
 */
public class MainActivity extends TabActivity {

  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    // load main view
    setContentView(R.layout.main_activity);

    // get the TabHost
    TabHost tabHost = getTabHost();

    // resusable TabSpec for each tab
    TabHost.TabSpec spec;

    // reusable Intent for each tab
    Intent intent;

    // first tab
    intent = new Intent(this, TabGroupActivity.class);
    spec = tabHost.newTabSpec("first")
        .setIndicator(createTabIndicatorView(tabHost, "First", R.drawable.ic_tab_first))
        .setContent(intent);
    tabHost.addTab(spec);

    // second tab
    intent = new Intent(this, TabGroupActivity.class);
    spec = tabHost.newTabSpec("second")
        .setIndicator(createTabIndicatorView(tabHost, "Second", R.drawable.ic_tab_second))
        .setContent(intent);
    tabHost.addTab(spec);

    tabHost.setCurrentTab(0);
  }

  /**
   * Creates tabs with custom layout.
   * 
   * @param tabHost the tab host
   * @param tabTitle the title of the tab
   * @param icon the icon of the tab
   * @return the view representing single tab
   */
  private View createTabIndicatorView(TabHost tabHost, CharSequence tabTitle, int icon) {
    LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View tabIndicator = inflater.inflate(R.layout.tab_indicator, tabHost, false);
    final TextView tv = (TextView) tabIndicator.findViewById(R.id.title);
    tv.setText(tabTitle);
    final ImageView iconView = (ImageView) tabIndicator.findViewById(R.id.icon);
    iconView.setImageDrawable(getResources().getDrawable(icon));
    return tabIndicator;
  }

}

The activty group:

/**
 * The purpose of this Activity is to manage the activities in a tab. Note:
 * Child Activities can handle Key Presses before they are seen here.
 */
public class TabGroupActivity extends ActivityGroup {

  private ArrayList<String> mIdList;

  public TabGroupActivity() {
  }

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (mIdList == null) {
      mIdList = new ArrayList<String>();
    }

    startChildActivity("firstChildActivity", new Intent(this, FirstChildActivity.class));
  }

  /**
   * This is called when a child activity of this one calls its finish method.
   * This implementation calls {@link LocalActivityManager#destroyActivity} on
   * the child activity and starts the previous activity. If the last child
   * activity just called finish(),this activity (the parent), calls finish to
   * finish the entire group.
   */
  @Override
  public void finishFromChild(Activity child) {
    LocalActivityManager manager = getLocalActivityManager();
    int index = mIdList.size() - 1;

    if (index < 1) {
      finish();
      return;
    }

    manager.destroyActivity(mIdList.get(index), true);
    mIdList.remove(index);
    index--;
    String lastId = mIdList.get(index);
    Intent lastIntent = manager.getActivity(lastId).getIntent();
    Window newWindow = manager.startActivity(lastId, lastIntent);
    setContentView(newWindow.getDecorView());
  }

  /**
   * Starts an Activity as a child Activity to this.
   * 
   * @param Id Unique identifier of the activity to be started.
   * @param intent The Intent describing the activity to be started.
   * @throws android.content.ActivityNotFoundException.
   */
  public void startChildActivity(String Id, Intent intent) {
    Window window = getLocalActivityManager().startActivity(Id,
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
    if (window != null) {
      mIdList.add(Id);
      setContentView(window.getDecorView());
    }
  }

  /**
   * The primary purpose is to prevent systems before
   * android.os.Build.VERSION_CODES.ECLAIR from calling their default
   * KeyEvent.KEYCODE_BACK during onKeyDown.
   */
  @Override
  public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
      // preventing default implementation previous to
      // android.os.Build.VERSION_CODES.ECLAIR
      return true;
    }
    return super.onKeyDown(keyCode, event);
  }

  /**
   * Overrides the default implementation for KeyEvent.KEYCODE_BACK so that all
   * systems call onBackPressed().
   */
  @Override
  public boolean onKeyUp(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
      onBackPressed();
      return true;
    }
    return super.onKeyUp(keyCode, event);
  }

  /**
   * If a Child Activity handles KeyEvent.KEYCODE_BACK. Simply override and add
   * this method.
   */
  @Override
  public void onBackPressed() {
    int length = mIdList.size();
    if (length > 1) {

      Activity current = getLocalActivityManager().getActivity(mIdList.get(length - 1));
      current.finish();

    } else {
      super.onBackPressed();
    }
  }

}