How to tag Activity

Question

I'm using this code to jump back in activity stack (mainly to move to home Activity):

Intent goTo = new Intent(this, HomeActivity.class);
goTo.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(goTo);

So I create new Intent and set "target" to HomeActivity which is in Activity stack so whole stack will be cleared from top to this HomeActivity.
Now I need slightly different use case. I have for example five Activities A-B-C-D-E (A started B etc.) on the stack. Now I need to jump from E to C or B depending of what user choose. The problem is that Activities A, B, C, D, E have same class. So I can't use example above because I don't know how to target that Activity.
So the question is if there is any way how to "tag activity" or manipulate with stack.
Thanks!

Answer 1

I haven't tried it myself, but I think the best option would be to refactor your app to use a stack of Fragments within a single Activity (since you can then more easily manage the backstack using the provided addToBackStack() and popBackStack() methods). Basically this involves moving most of the code in your Activity into a Fragment and then adding the backstack manipulation code in the Activity). You can look at the code for FragmentBreadCrumbs (with API 11+) or the code for HanselAndGretel (for use with the compatibility library) to see how this can be implemented.

However, if you want to continue using your current multi-Activity approach, the following is some code I came up with to illustrate how you can do this.

First, add several internal classes to alias your current Activity and put these classes into a sequence list (note also the simplistic getSequencedActivityIntent() method that I wrote, you can add more advanced logic if you need - maybe use a HashMap to associate each class in the sequence with an arbitrary tag value?):

public class MyActivity extends Activity {

    public static class A extends MyActivity {}
    public static class B extends MyActivity {}
    public static class C extends MyActivity {}
    public static class D extends MyActivity {}
    public static class E extends MyActivity {}
    public static class F extends MyActivity {}
    public static class G extends MyActivity {}
    public static class H extends MyActivity {}
    public static class I extends MyActivity {}
    public static class J extends MyActivity {}

    private final static List<Class<?>> SEQUENCE = Arrays.asList(new Class<?>[] {
            A.class, B.class, C.class, D.class, E.class,
            F.class, G.class, H.class, I.class, J.class,
    });

    private Intent getSequencedActivityIntent(int step) {
        final int current = SEQUENCE.indexOf(this.getClass());
        if (current == -1) new Intent(this, SEQUENCE.get(0));

        final int target = current + step;
        if (target < 0 || target > SEQUENCE.size() - 1) return null;

        return new Intent(this, SEQUENCE.get(target));
    }

    // the rest of your activity code
}

Don't forget to add their entries to your AndroidManifest.xml file too (singleTop is optional - it will prevent the Activity instance in the stack to be created again when brought back to the front):

    <activity android:name=".MyActivity$A" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$B" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$C" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$D" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$E" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$F" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$G" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$H" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$I" android:launchMode="singleTop" />
    <activity android:name=".MyActivity$J" android:launchMode="singleTop" />

Now, whenever you need to start a new "top" instance of your Activity, you can do something like:

    final Intent intent = getSequencedActivityIntent(+1);
    if (intent == null) return;
    intent.putExtra("dataset", dataSet);
    startActivity(intent);

And when you need to go back to one of the instance in the backstack you can do:

    final Intent intent = getSequencedActivityIntent(- stepBack);
    if (intent == null) return;
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    startActivity(intent);

Answer 2

You can index your activities without having to worry about handling all the chain of onActivityResults using a super Activity that you extend in all your activities

Here is an implementation (I did not test it) but if you extend this SuperActivity in all your Activities, you can call fallBackToActivity( int ) to any activity using its index and each activity now has a getIndex(). You can use it to fallback to a relative index like getIndex()-3

package sherif.android.stack.overflow;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

public class SuperActivity extends Activity {
    private static String EXTRA_INDEX = "SUPER_INDEX";
    private static int RESULT_FALLBACK = 0x123456;
    private int index;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(getIntent()!=null) {
            index = getIntent().getIntExtra(EXTRA_INDEX, -1) + 1;
        }
    }
    protected final int getIndex() {
        return index;
    }
    protected final void fallBackToActivity(int index) {
        Intent intent = new Intent();
        intent.putExtra(EXTRA_INDEX, index);
        setResult(RESULT_FALLBACK, intent);
        finish();
    }
    @Override
    public void startActivityForResult(Intent intent, int requestCode) {
        intent.putExtra(EXTRA_INDEX, getIndex());
        super.startActivityForResult(intent, requestCode);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(resultCode == RESULT_FALLBACK) {
            if(data.getIntExtra(EXTRA_INDEX, -1)!=getIndex()) {
                setResult(RESULT_FALLBACK, data);
                finish();
            }
        }
    }
}

Answer 3

You can just keep a condition in your statement if user chooses this item pass intent to B class and if user chooses that item pass intent to C class

Answer 4

Add extra to your intent that will point the activity what to do. For example

    intent.putExtra("STATE", 1);

And get this value in onCreate of your activity.

  getIntent().getExtras()