Intents and Intent Filters

Intents and Intent Filters

Intent types

Building an intent

<data/>

官方原文：Note: To receive implicit intents, you must include the CATEGORY_DEFAULT category in the intent filter. The methods startActivity() and startActivityForResult() treat all intents as if they declared the CATEGORY_DEFAULT category. If you do not declare this category in your intent filter, no implicit intents will resolve to your activity.

<intent-filters/>

Example explicit intent

Example implicit intent

Forcing an app chooser

Intent sendIntent = new Intent(Intent.ACTION_SEND);
Intent choose = Intent.createChooser(sendIntent, "Choose Application");
if (sendIntent.resolveActivity(getPackageManager()) != null) {
startActivity(choose);
}

Receiving an implicit intent

Example filters

<activity android:name="MainActivity">
<!-- This activity is the main entry, should appear in app launcher -->
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity>
<!-- This activity handles "SEND" actions with text data -->
<intent-filter>
<action android:name="android.intent.action.SEND"/>
<category android:name="android.intent.category.DEFAULT"/>
<data android:mimeType="text/plain"/>
</intent-filter>
<intent-filter>
<action>...</action>
</intent-filter>
</activity>

ACTION_MAIN

CATEGORY_LAUNCHER

system's app launcher

<intent-filter/>

Using a pending intent

// 向通知栏发送消息，执行Intent
Intent openIntent = new Intent(MainActivity.this, IntentActivity2.class);
PendingIntent pi = PendingIntent.getActivity(MainActivity.this, 0, openIntent, PendingIntent.FLAG_CANCEL_CURRENT);

NotificationManager nm = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
int icon = android.R.drawable.stat_notify_chat;
long when = System.currentTimeMillis() + 2000;
Notification n = new Notification.Builder(MainActivity.this)
.setContentIntent(pi)
.setDefaults(Notification.DEFAULT_SOUND)
.setTicker("Ticker")
.setContentTitle("ContentTitle")
.setContentText("ContentText")
.setSubText("SubText")
.setWhen(when)
.setSmallIcon(icon)
.build();

nm.notify(0, n);

Intent resolution

<action/>

<category/>

android.intent.category.DEFAULT

<data/>

<scheme>://<host>:<port>/<path>

URI线性依赖规则：
Each of these attributes is optional in a <data> element, but there are linear dependencies:
1. If a scheme is not specified, the host is ignored.
2. If a host is not specified, the port is ignored.
3. If both the scheme and host are not specified, the path is ignored.

URI最小匹配规则：
When the URI in an intent is compared to a URI specification in a filter, it's compared only to the parts of the URI included in the filter. For example:
1. If a filter specifies only a scheme, all URIs with that scheme match the filter.
2. If a filter specifies a scheme and an authority but no path, all URIs with the same scheme and authority pass the filter, regardless of their paths.
3. If a filter specifies a scheme, an authority, and a path, only URIs with the same scheme, authority, and path pass the filter.

Note: A path specification can contain a wildcard asterisk (*) to require only a partial match of the path name.

URI和MIME匹配规则：
The data test compares both the URI and the MIME type in the intent to a URI and MIME type specified in the filter. The rules are as follows:

An intent that contains neither a URI nor a MIME type passes the test only if the filter does not specify any URIs or MIME types.
An intent that contains a URI but no MIME type (neither explicit nor inferable from the URI) passes the test only if its URI matches the filter's URI format and the filter likewise does not specify a MIME type.
An intent that contains a MIME type but not a URI passes the test only if the filter lists the same MIME type and does not specify a URI format.
An intent that contains both a URI and a MIME type (either explicit or inferable from the URI) passes the MIME type part of the test only if that type matches a type listed in the filter. It passes the URI part of the test either if its URI matches a URI in the filter or if it has a content: or file: URI and the filter does not specify a URI. In other words, a component is presumed to support content: and file: data if its filter lists only a MIME type.

This last rule, rule (d), reflects the expectation that components are able to get local data from a file or content provider. Therefore, their filters can list just a data type and don't need to explicitly name the content: and file: schemes. The following example shows a typical case in which a <data> element tells Android that the component can get image data from a content provider and display it:

<intent-filter>
<data android:mimeType="image/*" />
...
</intent-filter>

**Filters that specify a data type but not a URI are perhaps the most common because most available data is dispensed by content providers.**

Another common configuration is a filter with a scheme and a data type. For example, a <data> element like the following tells Android that the component can retrieve video data from the network in order to perform the action:

<intent-filter>
<data android:scheme="http" android:type="video/*" />
...
</intent-filter>

Intent matching

PackageManager pm = getPackageManager();
Intent actIntent = new Intent("android.intent.action.MAIN");
actIntent.addCategory("android.intent.category.LAUNCHER");
List<ResolveInfo> acts = pm.queryIntentActivities(actIntent, 0);
for (ResolveInfo act : acts) {
Log.i(TAG, "Activity: " + act.activityInfo.name);
}

Intent srvIntent = new Intent("com.codesky.aidlgo.action.aidl.SERVER");
List<ResolveInfo> srvs = pm.queryIntentServices(srvIntent, 0);
for (ResolveInfo srv : srvs) {
Log.i(TAG, "Service: " + srv.serviceInfo.name);
}

通用的Intent

Alaram Clock

<uses-permission android:name="com.android.alarm.permission.SET_ALARM" />

<uses-permission android:name="com.android.alarm.permission.SET_ALARM" />

Calendar

Camera

Contacts/People App

Email

File Storage

Local Actions

Maps

Music or Video

New Note

Phone

Search

Settings

Text Messaging

Web Browser

Verify Intents with the Android Debug Bridge

adb shell am start -a <ACTION> -t <MIME_TYPE> -d <DATA> \
-e <EXTRA_NAME> <EXTRA_VALUE> -n <ACTIVITY>

例如:
adb shell am start -a android.intent.action.DIAL \
-d tel:555-5555 -n org.example.MyApp/.MyActivity