Android onActivityResult called early

问题:

I have 2 Activities, each in seperate applications. Activity1 has a button the user can click and it calls the second activity using an intent in its onClick() method:

Intent myIntent = getPackageManager().getLaunchIntentForPackage(com.myProject.Activity2);
startActivityForResult(myIntent, 600);

This correctly launches Activity2 from Activity1, but onActivityResult gets called in Activity1 before onCreate gets called in Activity2, instead of in onBackPressed() where I set up the return intent.

Here is the onCreate method for Activity2:

@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}

Here is the current version of onBackPressed method for Activity2:

@Override
public void onBackPressed() {
    Intent intent = new Intent();
    intent.putExtra("Stuff", someStuff);

    if(getParent()==null){
        setResult(Activity.RESULT_OK, intent);
    }else{
        getParent().setResult(Activity.RESULT_OK, intent);
    }
    finish();
    super.onBackPressed();
}

My AndroidManifest.xml has the following intent filter for Activity2:

<intent-filter>
    <action android:name="android.intent.action.MAIN"/>
    <category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>

I verified that my launchMode is standard (and not singleTask, etc) as advised here and my request code is not negative as warned here. I also tried android:launchMode="singleTop", but that was a no-go also.

I also tried not calling finish() in onBackPressed() for Activity2 as mentioned here (also with just super.onBackPressed() as suggested here) and again calling it as suggested here.

Additionally I tried commenting out the line intent.putExtra("Stuff", someStuff); as it seemed to cause trouble for this person.

Any ideas as to what I might be doing wrong?

回答1:

So here is the final solution that took care of it:

I changed the intent for Activity1 to the following:

Intent myIntent = new Intent();
myIntent.setClassName("com.myProject", "com.myProject.Activity2");
startActivityForResult(myIntent, 600);

For some reason Android requires the fully qualified name for the second parameter in addition to the package name given by the first parameter. Now it works! :)

回答2:

It will happen if "singleInstance" flag is set when you launch the activity.

回答3:

Not certain what your problem is. The way you're creating the Intent in Activity1 is odd; that method isn't meant for creating intents that launch another activity in the same app. Some developers use the Intent(Context, Class<>) constructor. I prefer to use Intent(String action) with a custom action string defined only in my app (which is easier to code correctly).

Also, the intent filter you've specified for Activity2 is usually used for an activity that's launched directly from the Home screen.

Where's the onCreate() code for activity2? Where's the code for onBackPressed()? Can you prove to me that setResult() is called before some other code in Activity2? You should run the activities in debug. Ensure that Activity2 is receiving the intent you think it should, then trace step by step the statements that are executed until setResult(). The thing not to do is throw solutions at the code before you understand what the underlying problem is.

As far as I can tell so far, Activity1 is sending out an Intent, and then onActivityResult is being called. Nothing else is proven so far.