How can i send back data using finish?

问题:

Like i can send data from one activity to another using this:

intent.putExtra("Name", Value);

how can i send data when i am using finish() to get back to the previous activity.

In my app from Activity_A i am going to Activity_B. In Activity_B i am marking a location on map, which gives me latitude and longitude. Then i want to use this lat and lng in Activity_A. But i don't want to get back to Activity_A using an intent, because i don't want to recreate the Activity_A since some data already filled will be lost.

回答1:

As you are using intent.putExtra("Name", Value);, use the same thing while finishing the activity also.

For ex.:

From activityA you call activityB like:

intent.putExtra("Name", Value);
now instead of startActivity() use `startActivityForResult()`

And from activityB, while finishing the activity, call:

setResult(RESULT_OK);

Now in activityA, your onActivityResult will be called, which is like:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // TODO Auto-generated method stub
}

So inthis way you can handle it.

回答2:

In Activity A:

// Add more, if you call different activities from Activity A
private static final REQUEST_GET_MAP_LOCATION = 0;

void doSomething() {
    ...
    startActivityForResult(theIntentYouUseToStartActivityB, REQUEST_GET_MAP_LOCATION);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_GET_MAP_LOCATION && resultCode == Activity.RESULT_OK) {
        int latitude = data.getIntExtra("latitude", 0);
        int longitude = data.getIntExtra("longitude", 0);
        // do something with B's return values
    }
}

In Activity B:

...
setResult(Activity.RESULT_OK, 
    new Intent().putExtra("latitude", latitude).putExtra("longitude", longitude));
finish();
...

回答3:

Call your Activity_B with startActivityForResult(), from your Activity_A:

 //Starting a new Intent
 Intent nextScreen = new Intent(getApplicationContext(), Activity_B.class);
 // starting new activity
 startActivityForResult(nextScreen,1000);

Once you finished working on the Activity_B, you call setResult() to set the data, followed by finish() like this

 //Starting the previous Intent
 Intent previousScreen = new Intent(getApplicationContext(), Activity_A.class);
 //Sending the data to Activity_A 
 previousScreen.putExtra("Bla"," Blabla"); 
 setResult(1000, previousScreen);
 finish();

This will bring you back to your previous Activity_A.

In Activity_A, override onActivityResult().

 @Override  
  protected void onActivityResult(int requestCode, int resultCode, Intent data)     
  {
     super.onActivityResult(requestCode, resultCode, data);
     String bla = data.getStringExtra("Bla");       
  }

Found here

回答4:

use startActivityForResult to start B and setResult before B finish and handle onAcitivityResult in A