我想知道Context.bindService()
何时返回false
?
我已尝试将onBind()
返回null
,但在调用true
且bindService
未执行时仍会返回onServiceConnected
。我也在Google网上论坛上看到了此消息
https://groups.google.com/forum/#!topic/android-developers/ZLl56Mz1jYg
我也找不到bindService的实现,因为它在Context.java中是抽象的,并且搜索“public boolean bindService”也不会产生任何有用的结果(最接近的是ApplicationContext,它似乎不存在于当前API级别。)
答案 0 :(得分:11)
binderService的实现位于android.app.ConntextImpl:
1412 public boolean bindService(Intent service, ServiceConnection conn, int flags, int userHandle) {
1413 IServiceConnection sd;
1414 if (conn == null) {
1415 throw new IllegalArgumentException("connection is null");
1416 }
1417 if (mPackageInfo != null) {
1418 sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),
1419 mMainThread.getHandler(), flags);
1420 } else {
1421 throw new RuntimeException("Not supported in system context");
1422 }
1423 try {
1424 IBinder token = getActivityToken();
1425 if (token == null && (flags&BIND_AUTO_CREATE) == 0 && mPackageInfo != null
1426 && mPackageInfo.getApplicationInfo().targetSdkVersion
1427 < android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
1428 flags |= BIND_WAIVE_PRIORITY;
1429 }
1430 service.setAllowFds(false);
1431 int res = ActivityManagerNative.getDefault().bindService(
1432 mMainThread.getApplicationThread(), getActivityToken(),
1433 service, service.resolveTypeIfNeeded(getContentResolver()),
1434 sd, flags, userHandle);
1435 if (res < 0) {
1436 throw new SecurityException(
1437 "Not allowed to bind to service " + service);
1438 }
1439 return res != 0;
1440 } catch (RemoteException e) {
1441 return false;
1442 }
1443 }
从第1431行开始,您可以看到它调用ActivityManagerNative的bindService 此实现位于com.android.server.am.ActivityManagerService:
11070 public int bindService(IApplicationThread caller, IBinder token,
11071 Intent service, String resolvedType,
11072 IServiceConnection connection, int flags, int userId) {
11073 enforceNotIsolatedCaller("bindService");
11074 // Refuse possible leaked file descriptors
11075 if (service != null && service.hasFileDescriptors() == true) {
11076 throw new IllegalArgumentException("File descriptors passed in Intent");
11077 }
11078
11079 synchronized(this) {
11080 return mServices.bindServiceLocked(caller, token, service, resolvedType,
11081 connection, flags, userId);
11082 }
11083 }
所以它最终调用了com.android.server.am.ActiveServices的bindeServiceLocked。
<强>更新强>
通过阅读binderServiceLocked()的代码:
472 ServiceLookupResult res =
473 retrieveServiceLocked(service, resolvedType,
474 Binder.getCallingPid(), Binder.getCallingUid(), userId, true);
475 if (res == null) {
476 return 0;
477 }
478 if (res.record == null) {
479 return -1;
480 }
发现如果retrieveServiceLocked()的结果为null,则返回false 检查retrieveServiceLocked()
的代码后721 ResolveInfo rInfo =
722 AppGlobals.getPackageManager().resolveService(
723 service, resolvedType,
724 ActivityManagerService.STOCK_PM_FLAGS, userId);
725 ServiceInfo sInfo =
726 rInfo != null ? rInfo.serviceInfo : null;
727 if (sInfo == null) {
728 Slog.w(TAG, "Unable to start service " + service + " U=" + userId +
729 ": not found");
730 return null;
731 }
发现如果无法获取Service的ResolveInfo,它将为false。
所以我尝试删除 AndroidManifest.xml 中的服务声明,并发现bindService()返回false。
答案 1 :(得分:3)
bindService返回false的一个非常常见的情况是服务不是declared in the Manifest。 在这种情况下,您应该将如下所示的代码添加到清单文件中
<manifest ... >
...
<application ... >
<service android:name=".ExampleService" />
...
</application>
</manifest>
答案 2 :(得分:0)
当您尝试调用已停止活动的 BindService (已经调用onStop)时,也会发生这种情况