How to capture the new Intent in onNewIntent()?

问题:

I want to pass a new, but different, Intent to an Activity. How do you differentiate between the new Intent and previous Intents? What kind of code goes into onNewIntent()? An example will be very helpful.

回答1:

The new intent comes as part of onNewIntent(Intent). The original Intent is still available via getIntent().

You put whatever code you need to into onNewIntent in order to update the UI with the new parameters; probably similar to what you're doing in onCreate.

Also, you probably want to call setIntent(intent) in onNewIntent to make sure future calls to getIntent() within the Activity lifecycle get the most recent Intent data.

回答2:

How an intent arrives at your activity depends on the launchMode (see the launchmode docs at http://developer.android.com/guide/topics/manifest/activity-element.html#lmode).

• For launchmode "standard" (the default) a startActivity with a new intent will result in an onCreate with that intent to a new instance of the activity.

• For launchmodes "singleTop" and "singleTask" a startActivity with a new intent will result in either

a) an onCreate with that intent to a new instance of the activity (if that activity was not running) [as per "standard" above] or b) an onNewIntent with that intent to the existing activity (if that activity was already runnning).

For b), the second intent is available in the onNewIntent parameters. What you do with it depends on your application. Some applications will just ignore it, while others will do a setIntent() and start re-initialization / update processing the new intent.

回答3:

Your Called Activity-Main Activity

public class MainActivity extends Activity
{
    public void onCreate(Bundle SavedInstanceState)
    {
    }

    @Override
    protected void onNewIntent(Intent intent) 
    {
        super.onNewIntent(intent);
        if(intent.getStringExtra("methodName").equals("myMethod"))
        {
            myMethod();
        }
    }

    public void myMethod()
    {
    }
}

Your Calling Activity

Code goes to Previous Intent

public class CallingActivity extends Activity
{
    public void onCreate(Bundle savedInstanceState)
    {
        Intent i=new Intent(this,MainActivity.class);
        i.putExtra("methodName","myMethod");//goes to previous INtent
        startActivity(i);//will trigger only myMethod in MainActivity
    }
}

Your Calling Activity

Code Starts New Activity using these kind of intent

public class CallingActivity extends Activity
{
    public void onCreate(Bundle savedInstanceState)
    {
        Intent i=new Intent(this,MainActivity.class);
        startActivity(i);//will trigger New Activity i.e. MainActivity
    }
}

回答4:

There's a bug related to this : http://code.google.com/p/android/issues/detail?id=17137

回答5:

If you don't want your activity to re-use the new intent in every subsequent onResume() I would recommend to store the intent in an instance field instead of via setIntent(intent).

That way you can reset that instance field to null once you have consumed the intent without throwing away the original launch intent.

More details in my answer here: https://stackoverflow.com/a/21261404/621690

setIntent(Intent) has been described as a mistake by an Android Framework Engineer: https://groups.google.com/forum/#!topic/android-developers/vrLdM5mKeoY