Mark Murphy - Beginning Android

• A result code from the child activity calling setResult(). Typically this is RESULT_OKor RESULT_CANCELLED, though you can create your own return codes (pick a number starting with RESULT_FIRST_USER).

• An optional Stringcontaining some result data, possibly a URL to some internal or external resource — for example, an ACTION_PICK Intenttypically returns the selected bit of content via this data string.

• An optional Bundlecontaining additional information beyond the result code and data string.

To demonstrate launching a peer activity, take a peek at the Activities/Launchsample application in the Source Code section at http://apress.com. The XML layout is fairly straightforward: two fields for the latitude and longitude, plus a button:

android:orientation="vertical"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

>

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:stretchColumns="1,2"

>

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:paddingLeft="2dip"

android:paddingRight="4dip"

android:text="Location:"

/>

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:cursorVisible="true"

android:editable="true"

android:singleLine="true"

android:layout_weight="1"

/>

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:cursorVisible="true"

android:editable="true"

android:singleLine="true"

android:layout_weight="1"

/>

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="Show Me!"

/>

The button’s OnClickListenersimply takes the latitude and longitude, pours them into a geoscheme Uri, then starts the activity.

packagecom.commonsware.android.activities;

importandroid.app.Activity;

importandroid.content.Intent;

importandroid.net.Uri;

importandroid.os.Bundle;

importandroid.view.View;

importandroid.widget.Button;

importandroid.widget.EditText;

public classLaunchDemo extendsActivity {

privateEditText lat;

privateEditText lon;

@Override

publicvoid onCreate(Bundle icicle) {

super. onCreate(icicle);

setContentView(R.layout.main);

Button btn = (Button) findViewById(R.id.map);

lat = (EditText) findViewById(R.id.lat);

lon = (EditText) findViewById(R.id.lon);

btn. setOnClickListener( newView. OnClickListener() {

publicvoid onClick(View view) {

String _lat = lat. getText(). toString();

String _lon = lon. getText(). toString();

Uri uri=Uri. parse("geo:"+_lat+","+_lon);

startActivity( new Intent(Intent.ACTION_VIEW, uri));

}

});

}

}

The activity is not much to look at (Figure 24-1).

Figure 24-1. The LaunchDemo sample application, with a location filled in

If you fill in a location (e.g., 38.8891 latitude and -77.0492 longitude) and click the button, the resulting map is more interesting (Figure 24-2). Note that this is the built-in Android map activity — we did not create our own activity to display this map.

Figure 24-2. The map launched by LaunchDemo, showing the Lincoln Memorial in Washington DC

In a Chapter 34, you will see how you can create maps in your own activities, in case you need greater control over how the map is displayed.

One of the main features of the modern desktop Web browser is tabbed browsing, where a single browser window can show several pages split across a series of tabs. On a mobile device this may not make a lot of sense, given that you lose screen real estate for the tabs themselves.

In this book, however, we do not let little things like sensibility stop us, so let me demonstrate a tabbed browser, using TabActivityand Intents.

As you may recall from Chapter 10, a tab can have either a Viewor an Activityas its content. If you want to use an Activityas the content of a tab, you provide an Intentthat will launch the desired Activity; Android’s tab-management framework will then pour the Activity’s user interface into the tab.

Your natural instinct might be to use an http:Urithe way we used a geo:Uriin the previous example:

Intent i = new Intent(Intent.ACTION_VIEW);

i. setData(Uri. parse("http://commonsware.com"));

That way, you could use the built-in Browser application and get all of the features that it offers.

Alas, this does not work. You cannot host other applications’ activities in your tabs — only your own activities, for security reasons.

So, we dust off our WebViewdemos from Chapter 13 and use those instead, repackaged as Activities/IntentTab.

Here is the source to the main activity, the one hosting the TabView:

public classIntentTabDemo extendsTabActivity {

@Override

publicvoid onCreate(Bundle savedInstanceState) {

super. onCreate(savedInstanceState);

TabHost host = getTabHost();

host. addTab(host. newTabSpec("one"). setIndicator("CW")

. setContent( new Intent( this, CWBrowser. class)));

host. addTab(host. newTabSpec("two"). setIndicator("Android")

. setContent( new Intent( this, AndroidBrowser. class)));