Question

I have a TabActivity that is the “base” Activity in my application. From the TabActivity a user can navigate through new Activities that are not a part of the original TabHost (I’m not messing around with TabGroups or anything like that).

My application also has a global options menu, from which a user should be able to navigate back to the original TabActivity and select a certain tab. For example, if the user selected the left-most options menu item, they would go to the left-most tab in the original TabActivity.

How can I accomplish this behavior? I do not want to start a new TabActivity because the original TabActivity has data propogated on it like Map points and a ListView. Ideally I would like to go back to that specific TabActivity. This movement can also occur at any point in the lifecycle, e.g.:

Original TabActivity -> Activity1 -> Activity2 -> Activity3 -> Activity n ->Back to Original TabActivity

Original TabActivity -> Activity1 -> Back to Original TabActivity

There can be any number of Activities launched in between the navigation. Therefore, calling finish() in the current Activity won’t satisfy this (as far as I know…).

My questions/concerns:

1. Primarily, how to accomplish this.
2. It is possible that the original TabActivity could be removed from the stack due to memory, correct? If so, how to deal with that? I assume if I figured out a way to locate the original TabActivity I could just do a check for null and if it’s not there, start a new TabActivity.

Answer 1

Figured this out. You should use launchMode="singleTask" in your Manifest for the specific Activity that you wish to switch back to. According to the Dev docs this routes back to that specific Activity if it exists.

So, in my Manifest, I have:

    <activity
        android:name=".MainTabsActivity"
        android:launchMode="singleTask"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.NoTitleBar" >
    </activity>

Then, in any Activity where you want to switch back to that TabActivity, just call a normal Intent. You can also use putExtra() to tell the TabActivity to switch to a new tab.

In a sub Activity:

        Intent mainTabsSearchIntent = new Intent(this, MainTabsActivity.class);
        mainTabsSearchIntent.putExtra("tabval", 0);
        startActivity(mainTabsSearchIntent);

This will either launch a new MainTabsActivity if the stack doesn’t have one or switch back to the old instance because of the launchMode="singleTask" parameter.

In order to provide the tab switching functionality, override onNewIntent(Intent intent) in your main TabActivity like so:

@Override
protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    Log.d(MyApplication.TAG, "Bringing this Activity back!");

    Bundle extras = intent.getExtras();
    if (extras != null) {
        tabHost.setCurrentTab(extras.getInt("tabval"));
        Log.d(MyApplication.TAG, "Switching to tab " + extras.getInt("tabval"));
    }
}

I hope this helps somebody that has a similar problem.