Mark Murphy - Beginning Android

The Android emulator does not have the ability to get a fix from GPS, triangulate your position from cell towers, or identify your location by some nearby WiFi signal. So, if you want to simulate a moving device, you will need to have some means of providing mock location data to the emulator.

For whatever reason, this particular area has undergone significant changes as Android itself has evolved. It used to be that you could provide mock location data within your application, which was very handy for demonstration purposes. Alas, those options have all been removed as of Android 1.0.

One likely option for supplying mock location data is the Dalvik Debug Monitor Service (DDMS). This is an external program, separate from the emulator, which can feed the emulator single location points or full routes to traverse, in a few different formats. DDMS is described in greater detail in Chapter 37.

One of Google’s most popular services — after search, of course — is Google Maps, where you can find everything from the nearest pizza parlor to directions from New York City to San Francisco (only 2,905 miles!) to street views and satellite imagery.

Android, not surprisingly, integrates Google Maps. There is a mapping activity available to users straight off the main Android launcher. More relevant to you, as a developer, are MapViewand MapActivity, which allow you to integrate maps into your own applications. Not only can you display maps, control the zoom level, and allow people to pan around, but you can tie in Android’s location-based services to show where the device is and where it is going.

Fortunately, integrating basic mapping features into your Android project is fairly easy. However, there is a fair bit of power available to you, if you want to get fancy.

Google Maps, particularly when integrated into third party applications, requires agreeing to a fairly lengthy set of legal terms. These terms include clauses that you may find unpalatable.

If you are considering Google Maps, please review these terms closely to determine if your intended use will not run afoul of any clauses. You are strongly recommended to seek professional legal counsel if there are any potential areas of conflict.

Also, keep your eyes peeled for other mapping options, based off of other sources of map data, such as OpenStreetMap. [32] http://www.openstreetmap.org/

Far and away the simplest way to get a map into your application is to create your own subclass of MapActivity. Like ListActivity, which wraps up some of the smarts behind having an activity dominated by a ListView, MapActivityhandles some of the nuances of setting up an activity dominated by a MapView.

In your layout for the MapActivitysubclass, you need to add an element named, at the time of this writing, com.google.android.maps.MapView. This is the “longhand” way to spell out the names of widget classes, by including the full package name along with the class name. This is necessary because MapViewis not in the com.google.android.widgetnamespace. You can give the MapViewwidget whatever android:idattribute value you want, plus handle all the layout details to have it render properly alongside your other widgets.

However, you do need to have:

• android:apiKey, which in production will need to be a Google Maps API key — more on this here

• android:clickable="true", if you want users to be able to click and pan through your map

For example, from the Maps/NooYawksample application, here is the main layout:

android:layout_width="fill_parent"

android:layout_height="fill_parent">

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:apiKey=""

android:clickable="true" />

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_alignParentLeft="true" />

We’ll cover that mysterious zoom LinearLayoutand the apiKeyin later sections of this chapter. In addition, you will need a couple of extra things in your AndroidManifest.xmlfile:

• The INTERNETand ACCESS_COARSE_LOCATIONpermissions

• Inside your , a element with android:name="com.google.android.maps", to indicate you are using one of the optional Android APIs

Here is the AndroidManifest.xmlfile for NooYawk:

package="com.commonsware.android.maps">

That is pretty much all you need for starters, plus to subclass your activity from MapActivity. If you were to do nothing else, and built that project and tossed it in the emulator, you’d get a nice map of the world. Note, however, that MapActivityis abstract — you need to implement isRouteDisplayed()to indicate if you are supplying some sort of driving directions or not.

In theory, the user could pan around the map using the directional pad. However, that’s not terribly useful when the user has the whole world in her hands.

Since a map of the world is not much good by itself, we need to add a few things…

You can find your MapViewwidget by findViewById(), no different than any other widget. The widget itself then offers a getMapController()method. Between the MapViewand MapController, you have a fair bit of capability to determine what the map shows and how it behaves. The following sections cover zoom and center, the features you will most likely want to use.

The map of the world you start with is rather broad. Usually, people looking at a map on a phone will be expecting something a bit narrower in scope, such as a few city blocks.

You can control the zoom level directly via the setZoom()method on the MapController. This takes an integer representing the level of zoom, where 1 is the world view and 21 is the tightest zoom you can get. Each level is a doubling of the effective resolution: 1 has the equator measuring 256 pixels wide, while 21 has the equator measuring 268,435,456 pixels wide. Since the phone’s display probably doesn’t have 268,435,456 pixels in either dimension, the user sees a small map focused on one tiny corner of the globe. A level of 16 will show you several city blocks in each dimension and is probably a reasonable starting point for you to experiment with.

If you wish to allow users to change the zoom level, you will need to do a few things:

• First, pick a spot on the screen where you want the zoom controls to appear. These are not huge, and they only appear when being used, so they can overlay the actual map itself if you choose. In the layout previously shown, for example, the zoom controls are placed over the map, in the lower-left corner of the screen. You should use a LinearLayoutor other simple container for the zoom controls’ position in your layout.

• In your activity’s onCreate()method, get your zoom controls’ container via findViewById().

• Add the result o f map.getZoomControls()to that container.