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09 Android包管理机制-PackageInstaller

09 Android包管理机制-PackageInstaller

作者: 凤邪摩羯 | 来源:发表于2021-02-19 09:38 被阅读0次

    前言

    这一篇文章我们接着学习PackageInstaller是如何安装APK的。本系列文章的源码基于Android8.0。

    1.PackageInstaller中的处理

    紧接着上一篇的内容,在PackageInstallerActivity调用startInstallConfirm方法初始化安装确认界面后,这个安装确认界面就会呈现给用户,用户如果想要安装这个应用程序就会点击确定按钮,就会调用PackageInstallerActivity的onClick方法,如下所示。
    packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java

    public void onClick(View v) {
            if (v == mOk) {
                if (mOk.isEnabled()) {
                    if (mOkCanInstall || mScrollView == null) {
                        if (mSessionId != -1) {
                            mInstaller.setPermissionsResult(mSessionId, true);
                            finish();
                        } else {
                            startInstall();//1
                        }
                    } else {
                        mScrollView.pageScroll(View.FOCUS_DOWN);
                    }
                }
            } else if (v == mCancel) {
                ...
                finish();
            }
        }
    

    onClick方法中分别对确定和取消按钮做处理,主要查看对确定按钮的处理,注释1处调用了startInstall方法:
    packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java

    private void startInstall() {
         Intent newIntent = new Intent();
         newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO,
                 mPkgInfo.applicationInfo);
         newIntent.setData(mPackageURI);//1
         newIntent.setClass(this, InstallInstalling.class);
         String installerPackageName = getIntent().getStringExtra(
                 Intent.EXTRA_INSTALLER_PACKAGE_NAME);
         if (mOriginatingURI != null) {
             newIntent.putExtra(Intent.EXTRA_ORIGINATING_URI, mOriginatingURI);
         }
         ...
         if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI);
         startActivity(newIntent);
         finish();
     }
    

    startInstall方法用于跳转到InstallInstalling这个Activity,并关闭掉当前的PackageInstallerActivity。InstallInstalling主要用于向包管理器发送包的信息并处理包管理的回调。 InstallInstalling的onCreate方法如下所示。
    packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java

    @Override
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.install_installing);
         ApplicationInfo appInfo = getIntent()
                 .getParcelableExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO);
         mPackageURI = getIntent().getData();
         if ("package".equals(mPackageURI.getScheme())) {
             try {
                 getPackageManager().installExistingPackage(appInfo.packageName);
                 launchSuccess();
             } catch (PackageManager.NameNotFoundException e) {
                 launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
             }
         } else {
         //根据mPackageURI创建一个对应的File 
             final File sourceFile = new File(mPackageURI.getPath());
             PackageUtil.initSnippetForNewApp(this, PackageUtil.getAppSnippet(this, appInfo,
                     sourceFile), R.id.app_snippet);
             //如果savedInstanceState不为null,获取此前保存的mSessionId和mInstallId       
             if (savedInstanceState != null) {//1
                 mSessionId = savedInstanceState.getInt(SESSION_ID);
                 mInstallId = savedInstanceState.getInt(INSTALL_ID);
               //向InstallEventReceiver注册一个观察者
                 try {
                     InstallEventReceiver.addObserver(this, mInstallId,
                             this::launchFinishBasedOnResult);//2
                 } catch (EventResultPersister.OutOfIdsException e) {
          
                 }
             } else {
                 PackageInstaller.SessionParams params = new PackageInstaller.SessionParams(
                         PackageInstaller.SessionParams.MODE_FULL_INSTALL);//3
                 params.referrerUri = getIntent().getParcelableExtra(Intent.EXTRA_REFERRER);
                 params.originatingUri = getIntent()
                         .getParcelableExtra(Intent.EXTRA_ORIGINATING_URI);
                 params.originatingUid = getIntent().getIntExtra(Intent.EXTRA_ORIGINATING_UID,
                         UID_UNKNOWN);
                 File file = new File(mPackageURI.getPath());//4
                 try {
                     PackageParser.PackageLite pkg = PackageParser.parsePackageLite(file, 0);//5
                     params.setAppPackageName(pkg.packageName);
                     params.setInstallLocation(pkg.installLocation);
                     params.setSize(
                             PackageHelper.calculateInstalledSize(pkg, false, params.abiOverride));
                 } catch (PackageParser.PackageParserException e) {
                    ...
                 }
                 try {
                     mInstallId = InstallEventReceiver
                             .addObserver(this, EventResultPersister.GENERATE_NEW_ID,
                                     this::launchFinishBasedOnResult);//6
                 } catch (EventResultPersister.OutOfIdsException e) {
                     launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
                 }
                 try {
                     mSessionId = getPackageManager().getPackageInstaller().createSession(params);//7
                 } catch (IOException e) {
                     launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
                 }
             }
              ...
             mSessionCallback = new InstallSessionCallback();
         }
     }
    

    onCreate方法中会分别对package和content协议的Uri进行处理,我们来看content协议的Uri处理部分。注释1处如果savedInstanceState不为null,获取此前保存的mSessionId和mInstallId,其中mSessionId是安装包的会话id,mInstallId是等待的安装事件id。注释2处根据mInstallId向InstallEventReceiver注册一个观察者,launchFinishBasedOnResult会接收到安装事件的回调,无论安装成功或者失败都会关闭当前的Activity(InstallInstalling)。如果savedInstanceState为null,代码的逻辑也是类似的,注释3处创建SessionParams,它用来代表安装会话的参数,注释4、5处根据mPackageUri对包(APK)进行轻量级的解析,并将解析的参数赋值给SessionParams。注释6处和注释2处类似向InstallEventReceiver注册一个观察者返回一个新的mInstallId,其中InstallEventReceiver继承自BroadcastReceiver,用于接收安装事件并回调给EventResultPersister。 注释7处PackageInstaller的createSession方法内部会通过IPackageInstaller与PackageInstallerService进行进程间通信,最终调用的是PackageInstallerService的createSession方法来创建并返回mSessionId。
    InstallInstalling的onCreate方法就分析到这,接着查看InstallInstalling的onResume方法:
    packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java

    @Override
     protected void onResume() {
         super.onResume();
         if (mInstallingTask == null) {
             PackageInstaller installer = getPackageManager().getPackageInstaller();
             PackageInstaller.SessionInfo sessionInfo = installer.getSessionInfo(mSessionId);//1
             if (sessionInfo != null && !sessionInfo.isActive()) {//2
                 mInstallingTask = new InstallingAsyncTask();
                 mInstallingTask.execute();
             } else {
                 mCancelButton.setEnabled(false);
                 setFinishOnTouchOutside(false);
             }
         }
     }
    

    注释1处根据mSessionId得到SessionInfo,SessionInfo代表安装会话的详细信息。注释2处如果sessionInfo不为Null并且不是活动的,就创建并执行InstallingAsyncTask。InstallingAsyncTask的doInBackground方法中会根据包(APK)的Uri,将APK的信息通过IO流的形式写入到PackageInstaller.Session中。InstallingAsyncTask的onPostExecute方法如下所示。
    packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java

    @Override
     protected void onPostExecute(PackageInstaller.Session session) {
         if (session != null) {
             Intent broadcastIntent = new Intent(BROADCAST_ACTION);
             broadcastIntent.setPackage(
                     getPackageManager().getPermissionControllerPackageName());
             broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId);
             PendingIntent pendingIntent = PendingIntent.getBroadcast(
                     InstallInstalling.this,
                     mInstallId,
                     broadcastIntent,
                     PendingIntent.FLAG_UPDATE_CURRENT);
             session.commit(pendingIntent.getIntentSender());//1
             mCancelButton.setEnabled(false);
             setFinishOnTouchOutside(false);
         } else {
             getPackageManager().getPackageInstaller().abandonSession(mSessionId);
             if (!isCancelled()) {
                 launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
             }
         }
     }
    

    创建了一个PendingIntent,并将该PendingIntent的IntentSender通过注释1处的PackageInstaller.Session的commit方法发送出去,发送去哪了呢?接着查看PackageInstaller.Session的commit方法。
    frameworks/base/core/java/android/content/pm/PackageInstaller.java

    public void commit(@NonNull IntentSender statusReceiver) {
               try {
                   mSession.commit(statusReceiver);
               } catch (RemoteException e) {
                   throw e.rethrowFromSystemServer();
               }
           }
    

    mSession的类型为IPackageInstallerSession,这说明要通过IPackageInstallerSession来进行进程间的通信,最终会调用PackageInstallerSession的commit方法,这样代码逻辑就到了Java框架层的。

    2.Java框架层的处理

    frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java

    @Override
       public void commit(IntentSender statusReceiver) {
           Preconditions.checkNotNull(statusReceiver);
           ...
           mActiveCount.incrementAndGet();
           final PackageInstallObserverAdapter adapter = new PackageInstallObserverAdapter(mContext,
                   statusReceiver, sessionId, mIsInstallerDeviceOwner, userId);
           mHandler.obtainMessage(MSG_COMMIT, adapter.getBinder()).sendToTarget();//1
       }
    

    commit方法中会将包的信息封装为PackageInstallObserverAdapter ,它在PMS中被定义。在注释1处会向Handler发送一个类型为MSG_COMMIT的消息,其中adapter.getBinder()会得到IPackageInstallObserver2.Stub类型的观察者,从类型就知道这个观察者是可以跨进程进行回调的。处理该消息的代码如下所示。
    frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java

    private final Handler.Callback mHandlerCallback = new Handler.Callback() {
          @Override
          public boolean handleMessage(Message msg) {
              final PackageInfo pkgInfo = mPm.getPackageInfo(
                      params.appPackageName, PackageManager.GET_SIGNATURES
                              | PackageManager.MATCH_STATIC_SHARED_LIBRARIES /*flags*/, userId);
              final ApplicationInfo appInfo = mPm.getApplicationInfo(
                      params.appPackageName, 0, userId);
              synchronized (mLock) {
                  if (msg.obj != null) {
                      mRemoteObserver = (IPackageInstallObserver2) msg.obj;//1
                  }
                  try {
                      commitLocked(pkgInfo, appInfo);//2
                  } catch (PackageManagerException e) {
                      final String completeMsg = ExceptionUtils.getCompleteMessage(e);
                      Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg);
                      destroyInternal();
                      dispatchSessionFinished(e.error, completeMsg, null);//3
                  }
                  return true;
              }
          }
      };
    

    注释1处获取IPackageInstallObserver2类型的观察者mRemoteObserver,注释2处的commitLocked方法如下所示。
    frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java

    private void commitLocked(PackageInfo pkgInfo, ApplicationInfo appInfo)
              throws PackageManagerException {
         ...
          mPm.installStage(mPackageName, stageDir, stageCid, localObserver, params,
                  installerPackageName, installerUid, user, mCertificates);
      }
    

    commitLocked方法比较长,这里截取最主要的信息,会调用PMS的installStage方法,这样代码逻辑就进入了PMS中。
    回到mHandlerCallback的handleMessage方法,如果commitLocked方法出现PackageManagerException异常,就会调用注释3处的dispatchSessionFinished方法,它的实现如下所示:
    frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java

    private void dispatchSessionFinished(int returnCode, String msg, Bundle extras) {
           mFinalStatus = returnCode;
           mFinalMessage = msg;
           if (mRemoteObserver != null) {
               try {
                   mRemoteObserver.onPackageInstalled(mPackageName, returnCode, msg, extras);//1
               } catch (RemoteException ignored) {
               }
           }
           ...
       }
    

    注释1处会调用IPackageInstallObserver2的onPackageInstalled方法,具体是实现在PackageInstallObserver类中:
    frameworks/base/core/java/android/app/PackageInstallObserver.java

    public class PackageInstallObserver {
        private final IPackageInstallObserver2.Stub mBinder = new IPackageInstallObserver2.Stub() {
            ...
            @Override
            public void onPackageInstalled(String basePackageName, int returnCode,
                    String msg, Bundle extras) {
                PackageInstallObserver.this.onPackageInstalled(basePackageName, returnCode, msg,
                        extras);//1
            }
        };
    

    注释1处调用了PackageInstallObserver的onPackageInstalled方法,实现这个方法的类为PackageInstallObserver的子类、前面提到的PackageInstallObserverAdapter。总结一下就是dispatchSessionFinished方法会通过mRemoteObserver的onPackageInstalled方法,将Complete方法出现的PackageManagerException的异常信息回调给PackageInstallObserverAdapter。

    3.总结

    本篇文章讲解了PackageInstaller安装APK的过程,简单来说就两步:

    1. 将APK的信息通过IO流的形式写入到PackageInstaller.Session中。
    2. 调用PackageInstaller.Session的commit方法,将APK的信息交由PMS处理。

    由于PMS中对APK安装的处理比较复杂,因此关于PMS的处理部分会在本系列的下一篇文章进行讲解。

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