BindService启动的Service为何在Activity销毁时自动解绑
以bindService启动服务后，直接退出Activity，日志会输出：
ActivityThread: Activity com.example.administrator.layoutmanager.MainActivity has leaked ServiceConnection com.example.administrator.layoutmanager.MainActivity 1@52816718thatwasoriginallyboundhereandroid.app.ServiceConnectionLeaked:Activitycom.example.administrator.layoutmanager.MainActivityhasleakedServiceConnectioncom.example.administrator.layoutmanager.MainActivity 1 @ 52816718 t h a t w a s o r i g i n a l l y b o u n d h e r e a n d r o i d . a p p . S e r v i c e C o n n e c t i o n L e a k e d : A c t i v i t y c o m . e x a m p l e . a d m i n i s t r a t o r . l a y o u t m a n a g e r . M a i n A c t i v i t y h a s l e a k e d S e r v i c e C o n n e c t i o n c o m . e x a m p l e . a d m i n i s t r a t o r . l a y o u t m a n a g e r . M a i n A c t i v i t y 1@52816718 that was originally bound here
紧接着就是我们服务的解绑与销毁
MyService: call onUnbind…
call onDestroy…
既然我们没去主动解绑，系统会帮我们解绑，那么它一定缓存了服务的connection。
所以我们先看下bindService的流程，看看在哪里保存了我们的Service信息，直接到ContextImpl中找bindService方法
@Override
public boolean bindService(Intent service, ServiceConnection conn,
int flags) {
warnIfCallingFromSystemProcess();
return bindServiceCommon(service, conn, flags, mMainThread.getHandler(),
Process.myUserHandle());
}bindServiceCommon方法：
private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags, Handler
handler, UserHandle user) {
// Keep this in sync with DevicePolicyManager.bindDeviceAdminServiceAsUser.
IServiceConnection sd;
if (conn == null) {
throw new IllegalArgumentException("connection is null");
}
if (mPackageInfo != null) {
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);
} else {
throw new RuntimeException("Not supported in system context");
}
validateServiceIntent(service);
try {
IBinder token = getActivityToken();
if (token == null && (flags&BIND_AUTO_CREATE) == 0 && mPackageInfo != null
&& mPackageInfo.getApplicationInfo().targetSdkVersion
< android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
flags |= BIND_WAIVE_PRIORITY;
}
service.prepareToLeaveProcess(this);
int res = ActivityManager.getService().bindService(
mMainThread.getApplicationThread(), getActivityToken(), service,
service.resolveTypeIfNeeded(getContentResolver()),
sd, flags, getOpPackageName(), user.getIdentifier());
if (res < 0) {
throw new SecurityException(
"Not allowed to bind to service " + service);
}
return res != 0;
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}代码很少，也不难理解，我们只管 看看 ServiceConnection 在哪里用到了 便知道 在哪里保存了。只有一行代码将其传了进去：
IServiceConnection sd;
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);我们继续点进去 发现点不进去，来看看这个mPackageInfo：
final @NonNull LoadedApk mPackageInfo;这个类最上面还有两个异常：
一个是IntentReceiver没有反注册，一个是ServiceConnection没有解绑。一切都答案都在这个类里了。
final class IntentReceiverLeaked extends AndroidRuntimeException {
public IntentReceiverLeaked(String msg) {
super(msg);
}
}
final class ServiceConnectionLeaked extends AndroidRuntimeException {
public ServiceConnectionLeaked(String msg) {
super(msg);
}
}LoadedApk类开头有一句注释：
/**
* Local state maintained about a currently loaded .apk.
* @hide
*/当前加载的apk的本地状态维护
来看看里面有些什么，emmm 应有尽有…
static final String TAG = "LoadedApk";
static final boolean DEBUG = false;
private final ActivityThread mActivityThread;
final String mPackageName;
private ApplicationInfo mApplicationInfo;
private String mAppDir;
private String mResDir;
private String[] mOverlayDirs;
private String[] mSharedLibraries;
private String mDataDir;
private String mLibDir;
private File mDataDirFile;
private File mDeviceProtectedDataDirFile;
private File mCredentialProtectedDataDirFile;
private final ClassLoader mBaseClassLoader;
private final boolean mSecurityViolation;
private final boolean mIncludeCode;
private final boolean mRegisterPackage;
private final DisplayAdjustments mDisplayAdjustments = new DisplayAdjustments();
/** WARNING: This may change. Don't hold external references to it. */
Resources mResources;
private ClassLoader mClassLoader;
private Application mApplication;
private String[] mSplitNames;
private String[] mSplitAppDirs;
private String[] mSplitResDirs;
private final ArrayMap> mReceivers
= new ArrayMap<>();
private final ArrayMap> mUnregisteredReceivers
= new ArrayMap<>();
private final ArrayMap> mServices
= new ArrayMap<>();
private final ArrayMap> mUnboundServices
= new ArrayMap<>();
我们接着 bindService的流程走，看看
mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);里面发生了什么
public final IServiceConnection getServiceDispatcher(ServiceConnection c,
Context context, Handler handler, int flags) {
synchronized (mServices) {
LoadedApk.ServiceDispatcher sd = null;
ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher> map = mServices.get(context);
if (map != null) {
if (DEBUG) Slog.d(TAG, "Returning existing dispatcher " + sd + " for conn " + c);
sd = map.get(c);
}
if (sd == null) {
sd = new ServiceDispatcher(c, context, handler, flags);
if (DEBUG) Slog.d(TAG, "Creating new dispatcher " + sd + " for conn " + c);
if (map == null) {
map = new ArrayMap<>();
mServices.put(context, map);
}
map.put(c, sd);
} else {
sd.validate(context, handler);
}
return sd.getIServiceConnection();
}
}代码中很清楚的的交代了， map.put(c, sd); 将ServiceConnection 存到了mServices当中。
然后看Activity在销毁时的处理，这里我就直接说代码位置，大家可以实际 去研究下Activity相关流程。
ActivityThread 的 handleDestroyActivity 中有一段代码：
if (c instanceof ContextImpl) {
((ContextImpl) c).scheduleFinalCleanup(
r.activity.getClass().getName(), "Activity");
}
//接下来
final void scheduleFinalCleanup(String who, String what) {
mMainThread.scheduleContextCleanup(this, who, what);
} final void scheduleContextCleanup(ContextImpl context, String who,
String what) {
ContextCleanupInfo cci = new ContextCleanupInfo();
cci.context = context;
cci.who = who;
cci.what = what;
sendMessage(H.CLEAN_UP_CONTEXT, cci);
}
//这个消息
case CLEAN_UP_CONTEXT:
ContextCleanupInfo cci = (ContextCleanupInfo)msg.obj;
cci.context.performFinalCleanup(cci.who, cci.what);
break;
//最后 来到
final void performFinalCleanup(String who, String what) {
//Log.i(TAG, "Cleanup up context: " + this);
mPackageInfo.removeContextRegistrations(getOuterContext(), who, what);
}mPackageInfo熟悉吗？绕了一圈 又来到了 LoadApk。我们来看removeContextRegistrations
public void removeContextRegistrations(Context context,
String who, String what) {
final boolean reportRegistrationLeaks = StrictMode.vmRegistrationLeaksEnabled();
synchronized (mReceivers) {
ArrayMap.ReceiverDispatcher> rmap =
mReceivers.remove(context);
if (rmap != null) {
for (int i = 0; i < rmap.size(); i++) {
LoadedApk.ReceiverDispatcher rd = rmap.valueAt(i);
IntentReceiverLeaked leak = new IntentReceiverLeaked(
what + " " + who + " has leaked IntentReceiver "
+ rd.getIntentReceiver() + " that was " +
"originally registered here. Are you missing a " +
"call to unregisterReceiver()?");
leak.setStackTrace(rd.getLocation().getStackTrace());
Slog.e(ActivityThread.TAG, leak.getMessage(), leak);
if (reportRegistrationLeaks) {
StrictMode.onIntentReceiverLeaked(leak);
}
try {
ActivityManager.getService().unregisterReceiver(
rd.getIIntentReceiver());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
mUnregisteredReceivers.remove(context);
}
synchronized (mServices) {
//Slog.i(TAG, "Receiver registrations: " + mReceivers);
ArrayMap.ServiceDispatcher> smap =
mServices.remove(context);
if (smap != null) {
for (int i = 0; i < smap.size(); i++) {
LoadedApk.ServiceDispatcher sd = smap.valueAt(i);
ServiceConnectionLeaked leak = new ServiceConnectionLeaked(
what + " " + who + " has leaked ServiceConnection "
+ sd.getServiceConnection() + " that was originally bound here");
leak.setStackTrace(sd.getLocation().getStackTrace());
Slog.e(ActivityThread.TAG, leak.getMessage(), leak);
if (reportRegistrationLeaks) {
StrictMode.onServiceConnectionLeaked(leak);
}
try {
ActivityManager.getService().unbindService(
sd.getIServiceConnection());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
sd.doForget();
}
}
mUnboundServices.remove(context);
//Slog.i(TAG, "Service registrations: " + mServices);
}
} 很明显 这里去 帮我们解绑 我们没有解绑的Receiver和Service，并输出异常。
到这里就基本结束了，现在来组织下语言：
- 为什么bindService可以跟Activity生命周期联动？
答： 因为bindService时LoadApk将ServiceConnection用map保存了起来，当Activity被destroy时会执行removeContextRegistrations来清除 该context的相关注册。所以Activity退出时服务也被解绑。
其余变量的用处可以自行参阅源码。