Develop Reference

Different types of Android Intents

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.

How can I know the startActivity intent from other application?

I have an Activity and assume that has been launched. When the other application use startActivity method to start my Activity, my Activity will show and run the onResume Method, but I can't find any way to get the intent which is used in startActivity method by the other application. I want to get the extra data in the intent. How can I do?
EDIT
My Activity is singleTask, and I want to get the startActivity intents form other applications. I think it is not associate with filters.

Have you tried using getIntent() ?
Then you can do:
this.getIntent().getExtras();
After that if you need new intents just override the onNewIntent function in your activity.

I simply say an example. When we need to share something. We click share button which shows a list of app by which we can share our things.
So, if you want to make that kind of app which can receive other app data then you need make your activity capable of receiving that data. In order to receive implicit intents, you must include the CATEGORY_DEFAULT category in the intent filter in manifest.
Below this link you will get some more information : http://developer.android.com/training/basics/intents/filters.html

Open my application from another in android

My boss asked me to prove that my application behaves properly when summoned by another application (dunno why he asked that).
So I have two apps here, one launches a second one. How I launch the specific app I want? Using Intent launch seemly any generic app that reaches a certain goal, not the app I really want.

Give this a try.
Intent secondIntent = new Intent();
secondIntent.setAction(Intent.ACTION_MAIN);
secondIntent.setClassName("com.example", "com.example.YourSecondApp");
startActivity(secondIntent);
I should point out that com.example should be the package of your second application (the one you want to call) and com.example.YourSecondapp is the class name where you have your onCreate() method.

Intent secondApp = new Intent("com.test.SecondApp");
startActivity(secondApp);
Check out for more examples
http://developer.android.com/resources/faq/commontasks.html#opennewscreen

Create one Intent using the following code
Explicit Intent
When you know the particular component(activity/service) to be loaded
Intent intent = new Intent();
intent.setClass("className/package name");
start<Activity/Service>(intent);
Imlicit Intent
When we do not have the idea which class to load and we know the Action to be perform by the launched application we can go with this intent.
Action needs to set, and the Android run time fallows the intent Resolution technique and list out(one or more components) the components to perform the action. from the list out components (if more than one), user will get the chance to launch his chosen application

Synchronous system activities

I wanna run two system activities one after another in specific order.
now as we know, startActivity is an asynchronous operation, so i cant keep on a specific order.
so i thought maybe I should try to do it with dialogBox in the middle but also running a dialogBox is an asynchronous.
now as i said the activities which i try to run are system activities, so i cant even start them with startActivityForResult (or mybe i can, but i cant think how it will help me).
Any tricks how could i manage with this issue?
Some code:
first activity:
Intent intent = new Intent();
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setAction(Settings.ACTION_APPLICATION_SETTINGS);
startActivity(intent);
second activity:
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setDataAndType(Uri.fromFile(tmpPackageFile
.getAbsoluteFile()),
"application/vnd.android.package-archive");
startActivity(intent);
as you can see, i dont have any access to those activites, i can just run thire intents from an outside class/activity/service.

You should be able to use startActivityForResult.. The second parameter to that function is a unique id, which you can use to track which activity is ending.
In onActivityResult of the calling activity, check which activity just finished, then start the next one with another call to startActivityForResult (or, if you don't care what happens with the 2nd, just startActivity).

I may be missing the boat on this, it seems you should place your code to start the second activity in the handler that finishes the first activity, such as on a button press or when an item is selected from a ListView. More information on how the first Activity is terminated would help.

Launching external application from my app

I would like to launch an app the user selects from within my application. However, I'm not sure how I'd go about doing this. I've tried this:
Intent intent = new Intent();
intent.setAction(Contacts.Intents.SHOW_OR_CREATE_CONTACT);
startActivity(intent);
But this seems to throw an error and force close my application. I also tried adding:
<action android:name="Contacts.Intents.SHOW_OR_CREATE_CONTACT"/>
in the AndroidManifest file, but to no avail.
A look at Logcat shows that it's an "IOexception - no such file or directory". A couple of questions arise from this. I read through the Android docs and noticed that the Contact.Intents class is deprecated. However, it's successor, ContactContracts is aimed at API level 5 whereas I'm targeting API level 3. Could this be the problem? Also, I've hardcoded this application into the code. Is there a way to retrieve the intents of any application the user selects so that they can be launched?

You need to pass extra information into the intent to tell Android what you want to show or create. Otherwise Android doesn't know what activity to start and (presumably in your case) throws an ActivityNotFoundException.
For a contact, you use the generic Intent.ACTION_INSERT_OR_EDIT then use the MIME type of an individual contact (Contacts.People.CONTENT_ITEM_TYPE).
For example:
Intent intent = new Intent(Intent.ACTION_INSERT_OR_EDIT);
intent.setType(People.CONTENT_ITEM_TYPE);
intent.putExtra(Contacts.Intents.Insert.PHONE, "+1234567890");
intent.putExtra(Contacts.Intents.Insert.PHONE_TYPE, Contacts.PhonesColumns.TYPE_MOBILE);
That will bring up the contacts app, prompting you to select an existing contact to add the phone number to, or to create a new contact.
You don't need to add anything special to your manifest to start external activities. Only if you were to directly manipulate the contacts ContentProvider would you need to add the appropriate CONTACT permissions to your manifest.

I use this code for that purpose:
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.setClassName("com.android.settings", "com.android.settings.Settings");
startActivity(intent);
This will launch the Settings app, you can use these also:
intent.setClassName("com.android.music", "com.android.music.MediaPlaybackActivityStarter");
intent.setClassName("com.android.contacts", "com.android.contacts.DialtactsContactsEntryActivity");
intent.setClassName("com.android.contacts", "com.android.contacts.DialtactsActivity");
The first starts the default music app, the second the contacts, and the third the dialer.
Hope this helps.

You need to pass in valid arguments to the apps you start. A lot of apps expect the data URI and / or certain extras to be valid.

Please try the following code:
Intent intent = new Intent(Contacts.Intents.SHOW_OR_CREATE_CONTACT);
this.startActivity(intent);
(sorry if there is something wrong on the syntax, I dont have android in this computer)
And remove the action from the manifest. that is not needed.
The action method is used for something else.
For more info, please look at the android site: http://developer.android.com/reference/android/content/Intent.html
Daniel

The activity you are calling should appear not only in the Manifest for its own package, but in the Manifest for the CALLING package, too.