how to modify smali code to delete 1 line in java code

Question

I want to delete the 580th and 581th line in the java code below. this file is in system/framework/services.jar in android devices, so the steps I did are:

1. decompile jar to smali

2. change the smali file

3. recompile the smali file to dex file

4. pack it into services.jar.

5. push services.jar into android mobile phone

   The question is in step2, how to change the smali file, I tried to delete :line580 and the code below it, but it doesn't work, when compiling, a nullPointerExecption was thrown...and I can see /error/ in jd-gui tool Somebody please give me some advices, I'm totally new to smali, thanks in advance.

The java code is:

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    }

The smali code after decompiling:

.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

Answer 1

Try to Remove

.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

I am not sure. But AFAIK this should remove line 580 and 581. Please try it and let me know.