I am trying to append certain data to an intent, before using StartActivityForResult on it.
When the intent returns in OnActivityForResult, I would like to access the data I appended in the intent. So I can correlate the data retrieved in the intent, with things like database entries, container ids, etc.
Unfortunately the intent that returns does not seem to be the same one I started. I tried comparing (==) the old and the new intent in a test case, and the result failed, and not surprisingly then the data I am trying append is not there. Is there any link back to the original intent?
Basic idea of what I've tried:
Code to StartActivityForResult in psuedo code:
Intent i = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI)
i.putExtra([-Key-], [int]);
i.putExtra([-Key-], [int]);
....
getParentFragment().startActivityForResult(i, requestCode);
Pseudo Code for OnActivityResult
#Override
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
....
switch(requestcode){
case RESULT_LOAD_IMAGE :
//These always evaluate to default. The intent returns with the picture,
//and I process it fine (with default values), but any extra data i try to append
//to the intent is lost.
int rowId = intent.getIntExtra([-Key-], [-def_value-]);
....
....
break;
default:
throw new RuntimeException();
}
}
When you launch an Activity using implicit Intent resolution, which is what you are doing when you do this:
Intent i = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI)
....
getParentFragment().startActivityForResult(i, requestCode);
you don't have any guarantees what Activity will actually be chosen to perform the action. Because of this, there isn't any "contract" between your Activity and the Activity that will be used to perform the desired action. This is, unfortunately, one of the disavantages of using implicit Intent resolution. Because there is no contract between the 2 Activities, you can't be sure what you are going to get in the result that is returned to you in onActivityResult().
If you look at the documentation for ACTION_PICK, it at least indicates what "should" happen (if the selected Activity actually behaves the way the documentation reads):
Input: getData() is URI containing a directory of data
(vnd.android.cursor.dir/*) from which to pick an item.
Output: The URI of the item that was picked.
This indicates that you should provide a URI that contains a directory of data and that you will be returned an Intent containing the URI of the item that was picked. That's it. That's all you can expect to get. You can put lots of other "extras" in the Intent that you pass to the Activity with ACTION_PICK, but that Activity doesn't care about those extras and will just ignore them. The Activity that performs the ACTION_PICK will create a new Intent containing the URI of the selected item and pass that back to you. It doesn't pass your original Intent back. The "input Intent" and the "output Intent" are completely different and don't have anything to do with each other.
To solve your problem, I'd suggest that you create a unique integer requestCode and save your "extras" in a table or map in your Activity associated with that requestCode. Then you can launch the ACTION_PICK activity using the requestCode. In onActivityResult() you can use the requestCode argument that comes back to find your "extras" that you saved and you'll be able to associate the returned URI with them.
NOTE: One more thing: When you call startActivityForResult() your Activity will be paused and the launched Activity will run. Your Activity won't be resumed until onActivityResult() is called. This means that you will only ever be able to have one ACTION_PICK pending at any given time. For this reason you may not need a way to associate a specific PICK action with any given data.
Related
I have recently started a new Android project and I'm working off the previous developer's code. I'm relatively new to Android and I've come across something that I'm unsure of.
What is the difference between this:
Intent intent = new Intent("com.example.project.MENU");
and this:
Intent intent = new Intent(this, DisplayMenu.class);
I understand what the 2nd code snippet does, I just can't get my head around as to what the first one is doing? Is it referencing the file in the package? Thanks
The first one is an implicit intent, while the second is an explicit intent.
The first one fired an Intent for the action com.example.project.MENU. If you look inside you project AndroidManifest.xml you can see some <intent-filter> balise. This baslise register activity, service or broadcast receiver to different actions.
This mecanism can be used to allow third party app to launch some of your activities.
You can see more on this tutorial http://www.vogella.com/tutorials/AndroidIntent/article.html#intenttypes
Basically an Intent carries some information that are used by the system in order to determine which component should be called for executing the action.
These information are:
Component name: the name of the component that should be launched. (If present the Intent is Explicit)
Action: it specifies the generic action that should be executed (es. ACTION_VIEW, ACTION_SEND). It determines how the rest of the intent is strucutred.
Data: represents the URI that refers to the object that should be associated with the action. For example with the action ACTION_EDIT, the Data should contain the URI of the document that you want modify.
Category: Additional infromation (for example if you want that your app is shown in the launcher you can use CATEGORY_LAUNCHER)
Extras: keys-values pairs that carries additional information
Flags: it is like a metadata that specify how the intent should be managed by the system.
The Intent class provides a lot of different constructors.
The first one you asked for is public Intent (String action)
So, this sets the Action, and lets null all other fields.
The second one public Intent (Context packageContext, Class<?> cls) creates an intent for a specific component by its Component name. All other fields are null. This is a Explicit Intent, since you declare exactly which component should receive it.
The first one is used when you need to call Intent from System
such as Open Camera, Gallery, or Share something to other Application
for example
// this one call Camera to Capture Image
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
// this one call gallery to let you select image
Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
and That MediaStore.something here is just a Path to the system
for example
MediaStore.ACTION_IMAGE_CAPTURE = "android.media.action.IMAGE_CAPTURE"
Intent.ACTION_PICK = "android.intent.action.PICK"
The first type of intent is mostly used if you want to open another application from your application while the second type of intent is used to open another activity in your application.
I have 5 intents in one activity. All of them are using the startActivityForResult. Because all of them are to correspond to different elements in the layout. How do I recognize which intent is the result for.
For e.g. If I have intent1, intent2, intent3 all of which are using startActivityForResult. After the Intent business is done. How do I now in my onActivityResult recognize which intent was called. The intent being called upon is the android phone contacts intent.
When you call startActivityForResult(), you set the requestCode. Later, you can use this request code inonActivityResult() to determine the intent. see What is Intent from onActivityResult Parameters for more. If you see the documentation of onActivityResult, it mentions:
protected void onActivityResult (int requestCode, int resultCode, Intent data)
requestCode: The integer request code originally supplied to startActivityForResult(), allowing you to identify who this result came from.
This is my first post, so please be nice :)
I have a question and no one gave the answer in the post I've seen.
My app has a list and a button to open an activity, this activity creates a new item to show in the list of the previous activity when pressing the button Create.
How can I do this?
This is the code I made for the first button:
intent = new Intent(this.getBaseContext(), NewTestActivity.class);
this.finish();
startActivity(intent);
and this is the code to go back an refresh:
Intent intent = new Intent(getBaseContext(), TestListActivity.class);
startActivity(intent);
But the code to goback is useful, because the activity don't refresh.
I have to call the new activity in a diferent way? Or go back to previus activity in a diferent way? Or go back normally and refresh the activity when I'm back in the previus activity?
Well...this is all.
Sorry for my bad english and, if this question has been answered in another thread, give me the link to read, because I can't find it :)
PS: I started with android in December.
Thanks for your help.
When you are going to start new activity you shouldn't close a current one until you actually need this behaviour. (remove this.finish(); row from your code)
Also you shouldn't close an active activity manually until you actually need it. When the user presses the "back" button on the device Android pops the previous activity from the "back stack". Read once more Activity documentation.
According to your description you have a list of elements. So in order to refresh the list you need to update your dataset and notify the list about it by ListView.notifyDataSetChanged() method call.
Before getting to a real answer, I'd like to show some improvements to your code.
First, when creating an Intent (or when you need a context in general) from an Activity there is no need to call getBaseContext(), you can just use this:
intent = new Intent(this, NewTestActivity.class);
Second, android is good at handling Activities, you do not have to close your first activity manually with finish(). Android will automatically pause or stop your first activity and bring it back when you return to it.
Third, in your case you might want to use startActivityForResult() instead of startActivity() for reasons I will explain below.
This will make your code look like the following:
private static final int MY_REQUEST_CODE = 33487689; //put this at the top of your Activity-class, with any unique value.
intent = new Intent(this, NewTestActivity.class);
startActivityForResult(intent, MY_REQUEST_CODE);
Now, the startActivityForResult() starts an activity and waits for a result from that new Activity. When you call finsih() in the new Activity you will end up in the first Activitys onActivityResult()-method, with data supplied from the new Activty that is now closed:
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if(requestCode != MY_REQUEST_CODE) return; //We got a result from another request, so for this example we can return.
if(resultCode != RESULT_OK) return; //The user aborted the action, so we won't get any data.
//After the above if-statements we know that the activity that gives us a result was requested with the correct request code, and it's action was successful, we can begin extracting the data, which is in the data-intent:
Item item = (Item) data.getSerializableExtra("customData"); //casts the data object to the custom Item-class. This can be any class, as long as it is serializable. There are many other kinds of data that can be put into an intent, but for this example a serializable was used.
itemList.add(item); //This is the list that was specified in onCreate()
//If you use an Adapter, this is the place to call notifyDataSetChanged();
}
For this all to work, we need to do some things in the second Activity:
When the item has been created, we must set a result:
//We begin by packing our item in an Intent (the Item class is an example that is expected to implement Serializable)
Item theCreatedItem; //This is what was created in the activity
Intent data = new Intent();
data.putSerializable(theCreatedItem);
setResult(RESULT_OK, data);
finish();
This should return to the first Activitys onActivityResult()-method with the item, as explained above.
I need something little different than usual.
I have like 20 buttons that can take image. I use same handler. Depending on what button clicked - I just pass "ButtonIndex" inside intent to camera. I would like to get that value back in OnActivityResult so I know what to process.
Is that possible? I tried to read from returned intent but value get's lost.
Yep. You can use startActivityForResult (Intent intent, int requestCode)
The requestcode will be returned when the activity exits.
I've got Activity A which fires up the Camera intent via:
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, REQUEST_CAMERA);
After the picture is taken I can easily grab the picture in:
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
But I'd like to receive the result in Activity B in which the image can be edited.
Right now I'm receiving the result in Activity A and pass it over to Activity B which results in showing the GUI of Activity A for a short while:
Intent i = new Intent().setAction("DisplayJPEG");
i.setClass(this, EditImageActivity.class);
i.putExtra("IMAGE_URI", uri);
startActivityForResult(i, REQUEST_EDIT_IMAGE);
Of course, I will need the result from Activity B in Activity A after the image has been edited. But that should work with:
setResult(resultCode, data);
So there has to be a way to do what I need. Please point me into the right direction.
Have you tried launching ActivityB, and in ActivityB onCreate event launch the Camera Intent?
You technically can't do what you're asking. You'll need to find a way to continue passing it the way you are and hide the UI or do as Pentium says and do it the other way around.
Edit: Nevermind, I misread how this works. What actually happens is you can use Activity A to start Activity B for result, but then if Activity B needs to start Activity C to continue processing whatever Activity A wanted, you can use FLAG_ACTIVITY_FORWARD_RESULT to make Activity C return its result to Activity A not B.
I haven't looked into this more than a quick glance, but I noticed an Intent flag called FLAG_ACTIVITY_FORWARD_RESULT which according to the documentation:
If set and this intent is being used to launch a new activity from an existing one, then the reply target of the existing activity will be transfered to the new activity. This way the new activity can call setResult(int) and have that result sent back to the reply target of the original activity.
Like I said, I haven't experimented with this, but that seems to suggest that you could launch your camera intent from Activity A but have it forward its result to Activity B.