注：本文翻譯自Google官方的Android Developers Training文檔，譯者技術(shù)一般，由于喜愛安卓而產(chǎn)生了翻譯的念頭，純屬個(gè)人興趣愛好。
原文鏈接： http://developer.android.com/training/location/activity-recognition.html
樣例代碼：
行為認(rèn)知會(huì)嘗試檢測(cè)當(dāng)前用戶的物理行為，比如：行走，駕駛或者靜止站立。從一個(gè)行為認(rèn)知客戶端發(fā)出更新信息的請(qǐng)求，同之前的定位或者地理圍欄所使用的定位客戶端相比有所不同，但大致思路是一致的。基于你所選擇的的更新間隔，定位服務(wù)會(huì)發(fā)出一個(gè)或更多個(gè)用戶當(dāng)前可能的行為信息，同時(shí)每一個(gè)信息都會(huì)有一個(gè)可能性級(jí)別。這節(jié)課將向你展示如何從定位服務(wù)實(shí)現(xiàn)用戶的行為識(shí)別。
一）. 請(qǐng)求行為認(rèn)知更新
從定位服務(wù)請(qǐng)求一個(gè)行為認(rèn)知更新與請(qǐng)求定期的地點(diǎn)更新是比較類似的。你通過(guò)客戶端發(fā)出請(qǐng)求，然后定位服務(wù)通過(guò)一個(gè) PendingIntent 將更新信息發(fā)回給你的應(yīng)用。然而，在你請(qǐng)求行為識(shí)別更新之前，你需要申請(qǐng)一些特別的權(quán)限，然后你使用不同類型的客戶端發(fā)出申請(qǐng)。下面各個(gè)章節(jié)將會(huì)講解如何請(qǐng)求權(quán)限，連接客戶端并請(qǐng)求更新。
申請(qǐng)就收更新的權(quán)限
一個(gè)應(yīng)用如果想要獲取行為認(rèn)知更新，必須有“ com.google.android.gms.permission.ACTIVITY_RECOGNITION ”的權(quán)限。要為你的權(quán)限請(qǐng)求這一權(quán)限，將下列的XML標(biāo)簽作為 <manifest> 標(biāo)簽的子標(biāo)簽添加到你的清單列表當(dāng)中：
<
uses-permission
android:name
="com.google.android.gms.permission.ACTIVITY_RECOGNITION"
/>
另外，行為認(rèn)知不需要 ACCESS_COARSE_LOCATION 權(quán)限和 ACCESS_FINE_LOCATION 權(quán)限。
檢查Google Play服務(wù)
位置服務(wù)是Google Play服務(wù)APK的其中一部分。由于用戶設(shè)備的狀態(tài)時(shí)難以預(yù)料的，你應(yīng)該一直在你嘗試連接定位服務(wù)之前，檢查APK是否已經(jīng)安裝。要檢查APK是否安裝，可以調(diào)用 GooglePlayServicesUtil.isGooglePlayServicesAvailable() ，它會(huì)返回一個(gè)整形的結(jié)果碼，其含義可以參閱： ConnectionResult 。如果你遇到了一個(gè)錯(cuò)誤，可以調(diào)用 GooglePlayServicesUtil.getErrorDialog() ，來(lái)獲取一個(gè)本地的對(duì)話框，引導(dǎo)用戶執(zhí)行正確地行為，之后將這一對(duì)話框顯示在一個(gè) DialogFragment 上。這一對(duì)話框可能允許用戶解決當(dāng)前的問(wèn)題，此時(shí)Google Play服務(wù)會(huì)發(fā)回一個(gè)結(jié)果到你的activity中。要處理這一結(jié)果，需要覆寫 onActivityResult() 方法。
Note：
要使你的應(yīng)用可以兼容1.6及以后版本的系統(tǒng)，顯示 DialogFragment 的activity必須是 FragmentActivity 的子類，而非 Activity 。使用 FragmentActivity 還可以允許你調(diào)用 getSupportFragmentManager() 方法來(lái)顯示 DialogFragment 。
由于你一直需要在你的代碼多個(gè)地方檢查Google Play服務(wù)，所以應(yīng)該定義一個(gè)方法將檢查行為進(jìn)行封裝，之后在每次連接嘗試之前進(jìn)行檢查。下面的代碼片段包含了檢查Google Play服務(wù)所需要的代碼：
public
class
MainActivity
extends
FragmentActivity {
...
//
Global constants
/*
* Define a request code to send to Google Play services
* This code is returned in Activity.onActivityResult
*/
private
final
static
int
CONNECTION_FAILURE_RESOLUTION_REQUEST
= 9000
;
...
//
Define a DialogFragment that displays the error dialog
public
static
class
ErrorDialogFragment
extends
DialogFragment {
//
Global field to contain the error dialog
private
Dialog mDialog;
//
Default constructor. Sets the dialog field to null
public
ErrorDialogFragment() {
super
();
mDialog
=
null
;
}
//
Set the dialog to display
public
void
setDialog(Dialog dialog) {
mDialog
=
dialog;
}
//
Return a Dialog to the DialogFragment.
@Override
public
Dialog onCreateDialog(Bundle savedInstanceState) {
return
mDialog;
}
}
...
/*
* Handle results returned to the FragmentActivity
* by Google Play services
*/
@Override
protected
void
onActivityResult(
int
requestCode,
int
resultCode, Intent data) {
//
Decide what to do based on the original request code
switch
(requestCode) {
...
case
CONNECTION_FAILURE_RESOLUTION_REQUEST :
/*
* If the result code is Activity.RESULT_OK, try
* to connect again
*/
switch
(resultCode) {
case
Activity.RESULT_OK :
/*
* Try the request again
*/
...
break
;
}
...
}
...
}
...
private
boolean
servicesConnected() {
//
Check that Google Play services is available
int
resultCode =
GooglePlayServicesUtil.
isGooglePlayServicesAvailable(
this
);
//
If Google Play services is available
if
(ConnectionResult.SUCCESS ==
resultCode) {
//
In debug mode, log the status
Log.d("Activity Recognition"
,
"Google Play services is available."
);
//
Continue
return
true
;
//
Google Play services was not available for some reason
}
else
{
//
Get the error dialog from Google Play services
Dialog errorDialog =
GooglePlayServicesUtil.getErrorDialog(
resultCode,
this
,
CONNECTION_FAILURE_RESOLUTION_REQUEST);
//
If Google Play services can provide an error dialog
if
(errorDialog !=
null
) {
//
Create a new DialogFragment for the error dialog
ErrorDialogFragment errorFragment =
new
ErrorDialogFragment();
//
Set the dialog in the DialogFragment
errorFragment.setDialog(errorDialog);
//
Show the error dialog in the DialogFragment
errorFragment.show(
getSupportFragmentManager(),
"Activity Recognition"
);
}
return
false
;
}
}
...
}
在后續(xù)章節(jié)的代碼片段中，都會(huì)調(diào)用這一方法來(lái)驗(yàn)證是否可獲取Google Play服務(wù)。
發(fā)送行文更新請(qǐng)求
從一個(gè)實(shí)現(xiàn)了定位服務(wù)所需要額回調(diào)函數(shù)的 Activity 或者 Fragment 發(fā)送更新請(qǐng)求。當(dāng)你請(qǐng)求連接到一個(gè)行為認(rèn)知客戶端時(shí)，最好將請(qǐng)求做成異步的進(jìn)程。當(dāng)客戶端已經(jīng)連接了，定位服務(wù)會(huì)調(diào)用你的 onConnected() 實(shí)現(xiàn)。在這個(gè)方法中，你可以將更新請(qǐng)求發(fā)送給定位服務(wù)；該請(qǐng)求是同步的。一旦你發(fā)出了請(qǐng)求，你可以關(guān)閉客戶端的連接。
整個(gè)過(guò)程會(huì)在下面的各個(gè)代碼片段中展開。
定義Activity或者Fragment
定義一個(gè) FragmentActivity 或者 Fragment 實(shí)現(xiàn)下列的接口：
當(dāng)客戶端連接或者斷開連接時(shí)定位服務(wù)調(diào)用的方法。
當(dāng)請(qǐng)求連接到客戶端時(shí)發(fā)生錯(cuò)誤，定位服務(wù)調(diào)用的方法。
例如：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
}
之后定義全局變量和常量。給更新間隔定義常量，為行為識(shí)別客戶端添加變量，同時(shí)還需要為定位服務(wù)發(fā)送更新時(shí)使用的
PendingIntent
添加另一個(gè)變量：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
//
Constants that define the activity detection interval
public
static
final
int
MILLISECONDS_PER_SECOND = 1000
;
public
static
final
int
DETECTION_INTERVAL_SECONDS = 20
;
public
static
final
int
DETECTION_INTERVAL_MILLISECONDS =
MILLISECONDS_PER_SECOND
*
DETECTION_INTERVAL_SECONDS;
...
/*
* Store the PendingIntent used to send activity recognition events
* back to the app
*/
private
PendingIntent mActivityRecognitionPendingIntent;
//
Store the current activity recognition client
private
ActivityRecognitionClient mActivityRecognitionClient;
...
}
在 onCreate() 中，實(shí)例化行為認(rèn)知客戶端以及 PendingIntent ：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
@Override
onCreate(Bundle savedInstanceState) {
...
/*
* Instantiate a new activity recognition client. Since the
* parent Activity implements the connection listener and
* connection failure listener, the constructor uses "this"
* to specify the values of those parameters.
*/
mActivityRecognitionClient
=
new
ActivityRecognitionClient(mContext,
this
,
this
);
/*
* Create the PendingIntent that Location Services uses
* to send activity recognition updates back to this app.
*/
Intent intent
=
new
Intent(
mContext, ActivityRecognitionIntentService.
class
);
/*
* Return a PendingIntent that starts the IntentService.
*/
mActivityRecognitionPendingIntent
=
PendingIntent.getService(mContext,
0
, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
...
}
...
}
開始請(qǐng)求進(jìn)程
定義一個(gè)方法來(lái)請(qǐng)求行為識(shí)別更新。在該方法中，請(qǐng)求一個(gè)到定位服務(wù)的連接。你可以在你的activity中任何地方調(diào)用該方法；其目標(biāo)是啟動(dòng)請(qǐng)求更新的一系列操作。
要保證競(jìng)爭(zhēng)情況的發(fā)生（當(dāng)你的應(yīng)用嘗試在第一個(gè)請(qǐng)求沒(méi)有執(zhí)行完畢時(shí)就啟動(dòng)另一個(gè)請(qǐng)求），定義一個(gè)布爾標(biāo)記變量，它跟蹤當(dāng)前請(qǐng)求的狀態(tài)。當(dāng)你開始請(qǐng)求時(shí)將它設(shè)置為 True ，當(dāng)請(qǐng)求完畢后，將它設(shè)置為 false 。
下面的代碼片段展示了如何啟動(dòng)一個(gè)更新請(qǐng)求：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
//
Global constants
...
//
Flag that indicates if a request is underway.
private
boolean
mInProgress;
...
@Override
onCreate(Bundle savedInstanceState) {
...
//
Start with the request flag set to false
mInProgress =
false
;
...
}
...
/**
* Request activity recognition updates based on the current
* detection interval.
*
*/
public
void
startUpdates() {
//
Check for Google Play services
if
(!
servicesConnected()) {
return
;
}
//
If a request is not already underway
if
(!
mInProgress) {
//
Indicate that a request is in progress
mInProgress =
true
;
//
Request a connection to Location Services
mActivityRecognitionClient.connect();
//
}
else
{
/*
* A request is already underway. You can handle
* this situation by disconnecting the client,
* re-setting the flag, and then re-trying the
* request.
*/
}
}
...
}
實(shí)現(xiàn) onConnected() 。在該方法中，從定位服務(wù)請(qǐng)求行為識(shí)別更新。當(dāng)定位服務(wù)完成了連接，并調(diào)用了 onConnected() ，更新請(qǐng)求會(huì)被立即調(diào)用：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
/*
* Called by Location Services once the location client is connected.
*
* Continue by requesting activity updates.
*/
@Override
public
void
onConnected(Bundle dataBundle) {
/*
* Request activity recognition updates using the preset
* detection interval and PendingIntent. This call is
* synchronous.
*/
mActivityRecognitionClient.requestActivityUpdates(
DETECTION_INTERVAL_MILLISECONDS,
mActivityRecognitionPendingIntent);
/*
* Since the preceding call is synchronous, turn off the
* in progress flag and disconnect the client
*/
mInProgress
=
false
;
mActivityRecognitionClient.disconnect();
}
...
}
處理連接斷開的情況
在一些情況下，定位服務(wù)可能會(huì)在你調(diào)用 disconnect() 之前就從行為識(shí)別客戶端就端開了連接。要處理這一情況，實(shí)現(xiàn) onDisconnected() 方法。在該方法中，對(duì)請(qǐng)求標(biāo)記變量進(jìn)行設(shè)置，來(lái)指出目前請(qǐng)求并不在流程中，然后刪除客戶端：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
/*
* Called by Location Services once the activity recognition
* client is disconnected.
*/
@Override
public
void
onDisconnected() {
//
Turn off the request flag
mInProgress =
false
;
//
Delete the client
mActivityRecognitionClient =
null
;
}
...
}
處理連接錯(cuò)誤
除了處理定位服務(wù)的常規(guī)回調(diào)函數(shù)外，你還需要提供一個(gè)回調(diào)函數(shù)，該函數(shù)會(huì)在連接錯(cuò)誤發(fā)生的時(shí)候被定為服務(wù)調(diào)用。該回調(diào)函數(shù)可以重用 DialogFragment 類（你在檢查Google Play服務(wù)時(shí)所定義的類）。同時(shí)它也可以重用當(dāng)用戶與錯(cuò)誤對(duì)話框交互時(shí)，接收任何由Google Play服務(wù)返回的結(jié)果的 onActivityResult() 函數(shù)。下面的代碼片段展示了該回調(diào)函數(shù)的一個(gè)例子：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
//
Implementation of OnConnectionFailedListener.onConnectionFailed
@Override
public
void
onConnectionFailed(ConnectionResult connectionResult) {
//
Turn off the request flag
mInProgress =
false
;
/*
* If the error has a resolution, start a Google Play services
* activity to resolve it.
*/
if
(connectionResult.hasResolution()) {
try
{
connectionResult.startResolutionForResult(
this
,
CONNECTION_FAILURE_RESOLUTION_REQUEST);
}
catch
(SendIntentException e) {
//
Log the error
e.printStackTrace();
}
//
If no resolution is available, display an error dialog
}
else
{
//
Get the error code
int
errorCode =
connectionResult.getErrorCode();
//
Get the error dialog from Google Play services
Dialog errorDialog =
GooglePlayServicesUtil.getErrorDialog(
errorCode,
this
,
CONNECTION_FAILURE_RESOLUTION_REQUEST);
//
If Google Play services can provide an error dialog
if
(errorDialog !=
null
) {
//
Create a new DialogFragment for the error dialog
ErrorDialogFragment errorFragment =
new
ErrorDialogFragment();
//
Set the dialog in the DialogFragment
errorFragment.setDialog(errorDialog);
//
Show the error dialog in the DialogFragment
errorFragment.show(
getSupportFragmentManager(),
"Activity Recognition"
);
}
}
...
}
...
}
二）. 處理行為更新
要處理每個(gè)更新間隔中定位服務(wù)發(fā)送的
Intent
，定義一個(gè)
IntentService
以及它所需要的方法
onHandleIntent()
。定位服務(wù)會(huì)將行為認(rèn)知更新以
Intent
對(duì)象的形式發(fā)出，當(dāng)你調(diào)用了
requestActivityUpdates()
后使用你提供的
PendingIntent
。一旦你為
PendingIntent
提供了一個(gè)顯式地intent，只有你定義的
IntentService
會(huì)接收你的intent。
下面的代碼片段闡述了如何在一個(gè)行為認(rèn)知更新中處理數(shù)據(jù)。
定義一個(gè)IntentService
首先定義類及其需要的方法 onHandleIntent() ：
/**
* Service that receives ActivityRecognition updates. It receives
* updates in the background, even if the main Activity is not visible.
*/
public
class
ActivityRecognitionIntentService
extends
IntentService {
...
/**
* Called when a new activity detection update is available.
*/
@Override
protected
void
onHandleIntent(Intent intent) {
...
}
...
}
之后，處理intent中的數(shù)據(jù)。從更新中，你可以獲取一個(gè)可能行為的列表以及每個(gè)行為的可能性級(jí)別。下面的代碼片段展示了如何獲取最可能的行為信息，行為的可能性級(jí)別和它的類型：
public
class
ActivityRecognitionIntentService
extends
IntentService {
...
@Override
protected
void
onHandleIntent(Intent intent) {
...
//
If the incoming intent contains an update
if
(ActivityRecognitionResult.hasResult(intent)) {
//
Get the update
ActivityRecognitionResult result =
ActivityRecognitionResult.extractResult(intent);
//
Get the most probable activity
DetectedActivity mostProbableActivity =
result.getMostProbableActivity();
/*
* Get the probability that this activity is the
* the user's actual activity
*/
int
confidence =
mostProbableActivity.getConfidence();
/*
* Get an integer describing the type of activity
*/
int
activityType =
mostProbableActivity.getType();
String activityName
=
getNameFromType(activityType);
/*
* At this point, you have retrieved all the information
* for the current update. You can display this
* information to the user in a notification, or
* send it to an Activity or Service in a broadcast
* Intent.
*/
...
}
else
{
/*
* This implementation ignores intents that don't contain
* an activity update. If you wish, you can report them as
* errors.
*/
}
...
}
...
}
方法 getNameFromType()會(huì)將activity類型轉(zhuǎn)換為帶有描述性的字符串。在一個(gè)需要發(fā)布的應(yīng)用中，你應(yīng)該從資源文件中獲取字符串而非使用固定的變量值：
public
class
ActivityRecognitionIntentService
extends
IntentService {
...
/**
* Map detected activity types to strings
*
@param
activityType The detected activity type
*
@return
A user-readable name for the type
*/
private
String getNameFromType(
int
activityType) {
switch
(activityType) {
case
DetectedActivity.IN_VEHICLE:
return
"in_vehicle"
;
case
DetectedActivity.ON_BICYCLE:
return
"on_bicycle"
;
case
DetectedActivity.ON_FOOT:
return
"on_foot"
;
case
DetectedActivity.STILL:
return
"still"
;
case
DetectedActivity.UNKNOWN:
return
"unknown"
;
case
DetectedActivity.TILTING:
return
"tilting"
;
}
return
"unknown"
;
}
...
}
在清單文件中指明IntentService
要在系統(tǒng)中指明 IntentService ，需要再應(yīng)用的清單文件中添加一個(gè) <service> 標(biāo)簽，例如：
<
service
android:name
="com.example.android.location.ActivityRecognitionIntentService"
android:label
="@string/app_name"
android:exported
="false"
>
</
service
>
注意，你不需要為該服務(wù)指定intent過(guò)濾器，因?yàn)樗鼉H會(huì)接收顯式的intent。如何創(chuàng)建接收的行為更新intent在之前的章節(jié)中已經(jīng)說(shuō)過(guò)了。
三）. 停止行為認(rèn)知更新
要停止行為認(rèn)知更新，其思路和請(qǐng)求更新是一致的，但是調(diào)用的函數(shù)是 removeActivityUpdates() 而不是 requestActivityUpdates() 。
由于移除更新會(huì)使用一些你在添加更新時(shí)所用到的方法，我們首先為兩個(gè)操作定義請(qǐng)求類型：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
public
enum
REQUEST_TYPE {START, STOP}
private
REQUEST_TYPE mRequestType;
...
}
修改啟動(dòng)行為認(rèn)知的代碼，這樣它就能使用“ START ”請(qǐng)求類型：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
public
void
startUpdates() {
//
Set the request type to START
mRequestType =
REQUEST_TYPE.START;
/*
* Test for Google Play services after setting the request type.
* If Google Play services isn't present, the proper request type
* can be restarted.
*/
if
(!
servicesConnected()) {
return
;
}
...
}
...
public
void
onConnected(Bundle dataBundle) {
switch
(mRequestType) {
case
START :
/*
* Request activity recognition updates using the
* preset detection interval and PendingIntent.
* This call is synchronous.
*/
mActivityRecognitionClient.requestActivityUpdates(
DETECTION_INTERVAL_MILLISECONDS,
mActivityRecognitionPendingIntent);
break
;
...
/*
* An enum was added to the definition of REQUEST_TYPE,
* but it doesn't match a known case. Throw an exception.
*/
default
:
throw
new
Exception("Unknown request type in onConnected()."
);
break
;
}
...
}
...
}
開始過(guò)程
定義一個(gè)方法，用來(lái)請(qǐng)求停止行為認(rèn)知更新。在該方法中，設(shè)置請(qǐng)求類型，并請(qǐng)求一個(gè)到定位服務(wù)的連接。你可以在你的activity的任何地方調(diào)用該方法；其目的是要開始一系列方法的調(diào)用來(lái)停止更新：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
/**
* Turn off activity recognition updates
*
*/
public
void
stopUpdates() {
//
Set the request type to STOP
mRequestType =
REQUEST_TYPE.STOP;
/*
* Test for Google Play services after setting the request type.
* If Google Play services isn't present, the request can be
* restarted.
*/
if
(!
servicesConnected()) {
return
;
}
//
If a request is not already underway
if
(!
mInProgress) {
//
Indicate that a request is in progress
mInProgress =
true
;
//
Request a connection to Location Services
mActivityRecognitionClient.connect();
//
}
else
{
/*
* A request is already underway. You can handle
* this situation by disconnecting the client,
* re-setting the flag, and then re-trying the
* request.
*/
}
...
}
...
}
在 onConnected() 方法中，如果請(qǐng)求類型是“ STOP ”，那么調(diào)用 removeActivityUpdates() 。將你用來(lái)啟動(dòng)更新的 PendingIntent 作為參數(shù)傳遞給 removeActivityUpdates() ：
public
class
MainActivity
extends
FragmentActivity
implements
ConnectionCallbacks, OnConnectionFailedListener {
...
public
void
onConnected(Bundle dataBundle) {
switch
(mRequestType) {
...
case
STOP :
mActivityRecognitionClient.removeActivityUpdates(
mActivityRecognitionPendingIntent);
break
;
...
}
...
}
...
}
你不需要修改 onDisconnected() 或 onConnectionFailed() 的實(shí)現(xiàn)，因?yàn)檫@些方法并不依賴于該請(qǐng)求類型。
現(xiàn)在你已經(jīng)有了一個(gè)行為認(rèn)知應(yīng)用的基本框架了。你可以將行為認(rèn)知的功能和其它定位相關(guān)的功能結(jié)合在一起，比如定期的地點(diǎn)更新，地理圍欄等，這些內(nèi)容都在這系列課程中的其它課中講授過(guò)了。
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