在什么情况下bindService返回false？

Question

我想知道什么时候Context.bindService()回来false？

我已经尝试进行onBind()返回null,但是true在bindService调用时它仍然会返回并且onServiceConnected不会执行.我也在Google网上论坛上看到了此消息,但没有回复 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的API级别中).

Answer 1

binderService的实现在android.app.ConntextImpl中:

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中:

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 .

更新:

通过读取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,则会出错.

于是,我就删除了服务宣言在AndroidManifest.xml中,如果发现bindService()返回false.

Answer 2

bindService 返回 false 的一种非常常见的情况是服务未在 Manifest 中声明。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>