How to reference child activity from TabHost to ca

问题:

I have a TabHost with two child activities in it (in two tabs). I also implemented a public function in one of these activities that i would like to call from my parent (TabHost), to trigger some action within the tab.

Is it possible to reference the activity itself from the TabHost to call a public function?

Thanks

here is my tabhost setup:

    res = getResources(); 
    tabHost = getTabHost(); 

    TabHost.TabSpec spec; 
    Intent intent;  

    intent = new Intent().setClass(this, home.class);
    spec = tabHost.newTabSpec("home").setIndicator("Groups", res.getDrawable(R.drawable.groups)).setContent(intent);
    tabHost.addTab(spec);
    intent = new Intent().setClass(this, messages.class);
    spec = tabHost.newTabSpec("messages").setIndicator("Messages", res.getDrawable(R.drawable.messages)).setContent(intent);    
    tabHost.addTab(spec);

回答1:

My approach would be to define a nested 'listener' class in the child activity which extends BroadcastReceiver.

I would then simply broadcast an Intent from my TabActivity which would then trigger the BroadcastReceiver to perform the action.

EDIT: To give example code...

The steps are...

1. Define the intent filter in the manifest
2. Add the nested 'listener' to the child activity
3. Set onResume()/onPause() in child activity to register/unregister the listener
4. Create intent in TabActivity and broadcast it when you want child to do something

In AndroidManifest.xml

<activity
    android:name=".MyActivity"
    android:label="@string/app_name"
    <intent-filter>
        <action android:name="com.mycompany.myApp.DO_SOMETHING" />
    </intent-filter>
</activity>

In MyActivity.java

public class MyActivity extends Activity {

    private MyListener listener = null;
    private Boolean MyListenerIsRegistered = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreated(savedInstanceState);

        listener = new MyListener();
    }

    @Override
    protected void onResume() {
        super.onResume();

        if (!MyListenerIsRegistered) {
            registerReceiver(listener, new IntentFilter("com.mycompany.myApp.DO_SOMETHING"));
            MyListenerIsRegisterd = true;
        }
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (MyListenerIsRegistered) {
            unregisterReceiver(listener);
            MyListenerIsRegistered = false;
        }
    }

    // Nested 'listener'
    protected class MyListener extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {

            // No need to check for the action unless the listener will
            // will handle more than one - let's do it anyway
            if (intent.getAction().equals("com.mycompany.myApp.DO_SOMETHING")) {
                // Do something
            }
        }
    }
}

In the main TabActivity

private void MakeChildDoSomething() {

    Intent i = new Intent();
    i.setAction("com.mycompany.myApp.DO_SOMETHING");
    sendBroadcast(i);
}

回答2:

I've found another, probably simpler solution. I'm sure OP doesn't need this any more, but maybe someone from the future will be glad to find it.

So, basically, to run a public method in your child activity, you just need this little piece of code in your parent (tabHost, home and message are taken from OP's TabHost configuration):

tabHost.setOnTabChangedListener(new TabHost.OnTabChangeListener() {
    @Override
    public void onTabChanged(String tabId) {
        Activity currentActivity = getCurrentActivity();
        if (currentActivity instanceof home) {
            ((home) currentActivity).aPublicMethodFromClassHome();
        }
        if (currentActivity instanceof messages) { 
            ((messages) currentActivity).aPublicMethodFromClassMessages();
        }
    }
});

I use it in my application. Works as a charm;)

回答3:

I'm currently debugging an Android application and came across the same need. I found a much straightforward answer to this with this code snippet :

String currentActivityId = getLocalActivityManager().getCurrentId();
Activity currentActivity = getLocalActivityManager().getActivity(currentActivityId);

The identifier here is the identifier given when creating the TabSpec :

tabHost.newTabSpec("id").setIndicator(indicator).setContent(intent);

回答4:

Thank you, this helped me to solve a simular problem!

Activity currentActivity = getLocalActivityManager().getActivity(_TabHost.getCurrentTabTag());
if(currentActivity != null && currentActivity instanceof iMyActivity)
{
// pass to children
((iMyActivity)currentActivity).onLaunchDelegate();
}

回答5:

From this link, I found this simple solution (http://androidactivity.wordpress.com/2012/08/17/two-way-communication-between-tabactivity-and-its-child-tabs/):

Well, the trick is to store the TAG associated with each tab, and use it to call the respective activity.

When you create the tab, you associate it with a tag like following:

yourTabHost.newTabSpec("Tab1");

Lets say we want to invoke a method “refreshContent()” that is inside the Tab1 Activity.

It’s simple as calling these lines from the MainActivity:

ActivityTab1 activity = (ActivityTab1) getLocalActivityManager().getActivity("Tab1");
 activity.refreshContent();

And that’s it!

Now for the opposite direction, we want to call some method “updateMain()” inside MainActivity, from the child tab TabActivity1.

At the TabActivity1 you will only need to call

((MainActivity)getParent()).updateMain();

回答6:

find it simple, use it in app ActivityTab class:

if(getCurrentActivity() instanceof YourSearchActivity){
            log("onClick: instance found");
            ((YourSearchActivity)getCurrentActivity()).activityPublicFuntion();
        }