Display maps with "Start activity" and other local mapping App
Durée estimée: 45 minutes
This App will "throw an intent" to draw a map. The Android system will catch ths intent and check if other Apps on the phone can do the job. If yes one will take control and do it. In our cas, this will be the Google maps App (if it is installed on the phone).
while this new "activity" is running, your own App will be hiddent and be back when this new activity has done the job and died.
What we will do :
What we will learn :
- Get a small peek on the Android activity life cycle, and how different Apps can run each other and take foreground control,
Input Resources :None : Start with a new project (no canvas necessary).
Intent APIs and interface to other Apps on your smartphone
With this solution, your App delegates mapping to another App that must be installed on your phone (here the Google maps App). The general idea of an “Intent” request is that an android App throws an intent (i.e. something it wishes to do) to the Android system and waits for some other App to answer ”I can do it”. If there is only one App, it will start, otherwise it will let you choose between App candidates do the job. That’s funny, as if Android Apps can behave like students in class when one calls for help, and others who know how propose to help !
In our case, we will ask for a "VIEWing" action (android.intent.action.VIEW). This with the data URI may be enough for Android to find the good App (as it is the case on my Nexus) but besides action and data URI it is better to say more precisely what service the App wants, or be more explicit.
With Activity Starter, you can indicate 3 infos :
- Action (android.intent.action.VIEW),
- Class (android.maps.MapsActivity)
- and Package (com.google.android.apps.maps).
The Data URI must match the API of the answering App. In our case with Google maps, the API and data URIs are described here.
They may be like :
geo:0,0?q=latitude,longitude(label)We will see details of this API when we use it below, and if you wish to know more you will find :
- a nice video tutorial by Ralph Morelli within the mobile CSP course (see lesson 10 in unit 3) with this video video to show the App and this video to show how to build it,
- a nice App on the playstore that may help you practice and find solutions : with App Inventor is the App Inventor ActivityStarter App. It may help you fill in parameters for the Activity starter component (even if you do not completely understand what you are really doing).
Code "Activity starter"display project with Google maps
If you have Apps like Google maps installed on you smartphone, you can start it from your own app with an "ActivityStarter" component (see in the Connectivity drawer).
There are 2 main differences with previous solution :
- your own App disappears while the new activity or App is running. This means that your App has completely lost control and can no longer interact until you close map display,
- but you have more display options and there is a good documentation for the API here.
- Create a new project,
- on the design side :
- Add a display button and set its text to "displayMap".
- Add a StartActivity component with the following setup :
Action : android.intent.action.VIEW
Activity Class : android.maps.MapsActivity
Activity Package : com.google.android.apps.maps
- On the blocks side :
- Initialize latitude, longitude and zoom global variables with default values, and add a query variable.
- Then build the data URI, according to the first case shown in the
Test App : Clicking on the button will display the map below on the right.
Go further : Other display options
The google maps Android-Intent API offers many other options (see documentation) :
|2.||geo:latitude,longitude?q=query||to add search for restaurant, hospital|
|3.||geo:0,0?q=my+street+address||to find by address|
|4.||geo:0,0?q=latitude,longitude(label)||to add a label|
|5.||google.navigation:q=a+street+address||to find directions with different travel modes|
|6.||google.navigation:q=latitude,longitude&mode=d||mode = d or w or b for travel option : |
drive, walk ,bike
Cases 1 to 7 are illustrated below them with their dataURIs.
The code - below -uses a list of 7 dataURIs. Display switches from one to the next each time the user clicks on the display button.