android api 26 ActivityManagerNative类被弃用。代理类ActivityManagerProxy已经被删除。改用AIDL方式。
今天撸源码：startActivity()。
发现了在API 26中： ActivityManagerNative类被弃用，代理类ActivityManagerProxy已经被删除。
本篇文章主要是记下，API26和API25的不同。
参考了文章：Activity启动过程详解
看到Instrumentation类的exeStartActivity时候，源码如下：
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode, Bundle options) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
Uri referrer = target != null ? target.onProvideReferrer() : null;
if (referrer != null) {
intent.putExtra(Intent.EXTRA_REFERRER, referrer);
}
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
intent.migrateExtraStreamToClipData();
intent.prepareToLeaveProcess(who);
int result = ActivityManager.getService()//注意这一行，和参考文章不同！
.startActivity(whoThread, who.getBasePackageName(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
token, target != null ? target.mEmbeddedID : null,
requestCode, 0, null, options);
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
return null;
} 
怎么两句话不同呢？其实原来我使用的api是26，而26之前的代码使用的是原作者写的。
继续深入看两个不同的代码：
26：
/**
* @hide
*/
public static IActivityManager getService() {
return IActivityManagerSingleton.get();
}
private static final Singleton IActivityManagerSingleton =
new Singleton() {
@Override
protected IActivityManager create() {
final IBinder b = ServiceManager.getService(Context.ACTIVITY_SERVICE);
final IActivityManager am = IActivityManager.Stub.asInterface(b);//注意这一行
return am;
}
}; 25：
static public IActivityManager getDefault() {
return gDefault.get();
}
private static final Singleton gDefault = new Singleton() {
protected IActivityManager create() {
IBinder b = ServiceManager.getService("activity");
if (false) {
Log.v("ActivityManager", "default service binder = " + b);
}
IActivityManager am = asInterface(b);//注意这一行
if (false) {
Log.v("ActivityManager", "default service = " + am);
}
return am;
}
}; 发现两个代码都是返回的IActivityManager。不同的是：
25中使用的是：静态方法asInterface，该方法属于ActivityManagerNative类。源码：
static public IActivityManager asInterface(IBinder obj) {
if (obj == null) {
return null;
}
IActivityManager in =
(IActivityManager)obj.queryLocalInterface(descriptor);
if (in != null) {
return in;
}
return new ActivityManagerProxy(obj);
}参考文章中说明了ActivityManagerNative类，还有ActivityManagerProxy类，是如何实现和AMS进程间通信的。最终使用ActivityManagerProxy代理类实现了startActivity。具体见参考文章：Activity启动过程详解。
26中使用的是：
IActivityManager.Stub.asInterface(b);而我们再看api26中的ActivityManagerNative类。源码已经很少：
/**
* {@hide}
* @deprecated will be removed soon. See individual methods for alternatives.//注意解释
*/
@Deprecated
public abstract class ActivityManagerNative {
/**
* Cast a Binder object into an activity manager interface, generating
* a proxy if needed.
*
* @deprecated use IActivityManager.Stub.asInterface instead.//注意解释
*/
static public IActivityManager asInterface(IBinder obj) {
return IActivityManager.Stub.asInterface(obj);
}
/**
* Retrieve the system's default/global activity manager.
*
* @deprecated use ActivityManager.getService instead.
*/
static public IActivityManager getDefault() {
return ActivityManager.getService();
}
/**
* Convenience for checking whether the system is ready. For internal use only.
*
* @deprecated use ActivityManagerInternal.isSystemReady instead.
*/
static public boolean isSystemReady() {
return ActivityManager.isSystemReady();
}
/**
* @deprecated use ActivityManager.broadcastStickyIntent instead.
*/
static public void broadcastStickyIntent(Intent intent, String permission, int userId) {
broadcastStickyIntent(intent, permission, AppOpsManager.OP_NONE, userId);
}
/**
* Convenience for sending a sticky broadcast. For internal use only.
* If you don't care about permission, use null.
*
* @deprecated use ActivityManager.broadcastStickyIntent instead.
*/
static public void broadcastStickyIntent(Intent intent, String permission, int appOp,
int userId) {
ActivityManager.broadcastStickyIntent(intent, appOp, userId);
}
/**
* @deprecated use ActivityManager.noteWakeupAlarm instead.
*/
static public void noteWakeupAlarm(PendingIntent ps, int sourceUid, String sourcePkg,
String tag) {
ActivityManager.noteWakeupAlarm(ps, sourceUid, sourcePkg, tag);
}
/**
* @deprecated use ActivityManager.noteAlarmStart instead.
*/
static public void noteAlarmStart(PendingIntent ps, int sourceUid, String tag) {
ActivityManager.noteAlarmStart(ps, sourceUid, tag);
}
/**
* @deprecated use ActivityManager.noteAlarmFinish instead.
*/
static public void noteAlarmFinish(PendingIntent ps, int sourceUid, String tag) {
ActivityManager.noteAlarmFinish(ps, sourceUid, tag);
}
}解释说这个类已经被弃用，方法都可以用ActivityManager来中的代替。
而且代理类ActivityManagerProxy已经被删除！
小结：API26中启动Activity时候，和AMS通信机制已经被改成AIDL方式！
扩展思考：
1、其实通过看aidl 自动生成文件，可以看出，
stub.asInterface其实调用的也是queryLocalInterface，api25和api26的本质是一样的。
2、api26中只有ServiceManagerNative还没有被弃用。
25中使用的：
ApplicationThreadNative、
ActivityManagerNative、
BulkCursorNative、
ContentProviderNative、
都已经不在使用。