我想删除下面java代码中的第580行和第581行。这个文件在android设备的system/framework/services.jar中，所以我做的步骤是：
将jar反编译为smali
修改smali文件
将smali文件重新编译为dex文件
将其打包到 services.jar 中。
将services.jar推送到安卓手机
问题在第2步，如何更改smali文件，我试图删除:line580和它下面的代码，但它不起作用，编译时抛出了一个nullPointerExecption......我可以看到/错误/在jd-gui工具有人请给我一些建议，我对smali完全陌生，在此先感谢。
java代码是：
568 public void registerUiTestAutomationService(IBinder owner,
569 IAccessibilityServiceClient serviceClient,
570 AccessibilityServiceInfo accessibilityServiceInfo) {
571 mSecurityPolicy.enforceCallingPermission(Manifest.permission.RETRIEVE_WINDOW_CONTENT,
572 FUNCTION_REGISTER_UI_TEST_AUTOMATION_SERVICE);
573
574 accessibilityServiceInfo.setComponentName(sFakeAccessibilityServiceComponentName);
575
576 synchronized (mLock) {
577 UserState userState = getCurrentUserStateLocked();
578
579 if (userState.mUiAutomationService != null) {
580 throw new IllegalStateException("UiAutomationService " + serviceClient
581 + "already registered!");
582 }
583
584 try {
585 owner.linkToDeath(userState.mUiAutomationSerivceOnwerDeathRecipient, 0);
586 } catch (RemoteException re) {
587 Slog.e(LOG_TAG, "Couldn't register for the death of a"
588 + " UiTestAutomationService!", re);
589 return;
590 }
591
592 userState.mUiAutomationServiceOwner = owner;
593 userState.mUiAutomationServiceClient = serviceClient;
594
595 // Set the temporary state.
596 userState.mIsAccessibilityEnabled = true;
597 userState.mIsTouchExplorationEnabled = false;
598 userState.mIsEnhancedWebAccessibilityEnabled = false;
599 userState.mIsDisplayMagnificationEnabled = false;
600 userState.mInstalledServices.add(accessibilityServiceInfo);
601 userState.mEnabledServices.clear();
602 userState.mEnabledServices.add(sFakeAccessibilityServiceComponentName);
603 userState.mTouchExplorationGrantedServices.add(sFakeAccessibilityServiceComponentName);
604
605 // Use the new state instead of settings.
606 onUserStateChangedLocked(userState);
607 }
608 }
反编译后的smali代码：
.line 579
.local v1, "userState":Lcom/android/server/accessibility/AccessibilityManagerService$UserState;
# getter for: Lcom/android/server/accessibility/AccessibilityManagerService$UserState;->mUiAutomationService:Lcom/android/server/accessibility/AccessibilityManagerService$Service;
invoke-static {v1}, Lcom/android/server/accessibility/AccessibilityManagerService$UserState;->access$300(Lcom/android/server/accessibility/AccessibilityManagerService$UserState;)Lcom/android/server/accessibility/AccessibilityManagerService$Service;
move-result-object v2
if-eqz v2, :cond_3d
.line 580
new-instance v2, Ljava/lang/IllegalStateException;
new-instance v4, Ljava/lang/StringBuilder;
invoke-direct {v4}, Ljava/lang/StringBuilder;-><init>()V
const-string v5, "UiAutomationService "
invoke-virtual {v4, v5}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v4
invoke-virtual {v4, p2}, Ljava/lang/StringBuilder;->append(Ljava/lang/Object;)Ljava/lang/StringBuilder;
move-result-object v4
const-string v5, "already registered!"
invoke-virtual {v4, v5}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v4
invoke-virtual {v4}, Ljava/lang/StringBuilder;->toString()Ljava/lang/String;
move-result-object v4
invoke-direct {v2, v4}, Ljava/lang/IllegalStateException;-><init>(Ljava/lang/String;)V
throw v2
.line 607
.end local v1 # "userState":Lcom/android/server/accessibility/AccessibilityManagerService$UserState;
:catchall_3a
move-exception v2
monitor-exit v3
:try_end_3c
.catchall {:try_start_11 .. :try_end_3c} :catchall_3a
throw v2
.line 585
.restart local v1 # "userState":Lcom/android/server/accessibility/AccessibilityManagerService$UserState;
:cond_3d
:try_start_3d
# getter for: Lcom/android/server/accessibility/AccessibilityManagerService$UserState;->mUiAutomationSerivceOnwerDeathRecipient:Landroid/os/IBinder$DeathRecipient;
invoke-static {v1}, Lcom/android/server/accessibility/AccessibilityManagerService$UserState;->access$1200(Lcom/android/server/accessibility/AccessibilityManagerService$UserState;)Landroid/os/IBinder$DeathRecipient;
move-result-object v2
const/4 v4, 0x0
invoke-interface {p1, v2, v4}, Landroid/os/IBinder;->linkToDeath(Landroid/os/IBinder$DeathRecipient;I)V
:try_end_45
.catch Landroid/os/RemoteException; {:try_start_3d .. :try_end_45} :catch_74
.catchall {:try_start_3d .. :try_end_45} :catchall_3a