- Android框架层
- Android包管理机制
- Android框架层
本文首发于微信公众号「刘望舒」
前言
在本系列上一篇文章Android包管理机制（一）PackageInstaller的初始化中我们学习了PackageInstaller是如何初始化的，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
1public void onClick(View v) { 2 if (v == mOk) { 3 if (mOk.isEnabled()) { 4 if (mOkCanInstall || mScrollView == null) { 5 if (mSessionId != -1) { 6 mInstaller.setPermissionsResult(mSessionId, true); 7 finish(); 8 } else { 9 startInstall();//1 10 } 11 } else { 12 mScrollView.pageScroll(View.FOCUS_DOWN); 13 } 14 } 15 } else if (v == mCancel) { 16 ... 17 finish(); 18 } 19 }
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
1 private void startInstall() { 2 Intent newIntent = new Intent(); 3 newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO, 4 mPkgInfo.applicationInfo); 5 newIntent.setData(mPackageURI);//1 6 newIntent.setClass(this, InstallInstalling.class); 7 String installerPackageName = getIntent().getStringExtra( 8 Intent.EXTRA_INSTALLER_PACKAGE_NAME); 9 if (mOriginatingURI != null) { 10 newIntent.putExtra(Intent.EXTRA_ORIGINATING_URI, mOriginatingURI); 11 } 12 ... 13 if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI); 14 startActivity(newIntent); 15 finish(); 16 }
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
1 @Override 2 protected void onCreate(@Nullable Bundle savedInstanceState) { 3 super.onCreate(savedInstanceState); 4 setContentView(R.layout.install_installing); 5 ApplicationInfo appInfo = getIntent() 6 .getParcelableExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO); 7 mPackageURI = getIntent().getData(); 8 if ("package".equals(mPackageURI.getScheme())) { 9 try { 10 getPackageManager().installExistingPackage(appInfo.packageName); 11 launchSuccess(); 12 } catch (PackageManager.NameNotFoundException e) { 13 launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null); 14 } 15 } else { 16 //根据mPackageURI创建一个对应的File 17 final File sourceFile = new File(mPackageURI.getPath()); 18 PackageUtil.initSnippetForNewApp(this, PackageUtil.getAppSnippet(this, appInfo, 19 sourceFile), R.id.app_snippet); 20 //如果savedInstanceState不为null，获取此前保存的mSessionId和mInstallId 21 if (savedInstanceState != null) {//1 22 mSessionId = savedInstanceState.getInt(SESSION_ID); 23 mInstallId = savedInstanceState.getInt(INSTALL_ID); 24 //向InstallEventReceiver注册一个观察者 25 try { 26 InstallEventReceiver.addObserver(this, mInstallId, 27 this::launchFinishBasedOnResult);//2 28 } catch (EventResultPersister.OutOfIdsException e) { 29 30 } 31 } else { 32 PackageInstaller.SessionParams params = new PackageInstaller.SessionParams( 33 PackageInstaller.SessionParams.MODE_FULL_INSTALL);//3 34 params.referrerUri = getIntent().getParcelableExtra(Intent.EXTRA_REFERRER); 35 params.originatingUri = getIntent() 36 .getParcelableExtra(Intent.EXTRA_ORIGINATING_URI); 37 params.originatingUid = getIntent().getIntExtra(Intent.EXTRA_ORIGINATING_UID, 38 UID_UNKNOWN); 39 File file = new File(mPackageURI.getPath());//4 40 try { 41 PackageParser.PackageLite pkg = PackageParser.parsePackageLite(file, 0);//5 42 params.setAppPackageName(pkg.packageName); 43 params.setInstallLocation(pkg.installLocation); 44 params.setSize( 45 PackageHelper.calculateInstalledSize(pkg, false, params.abiOverride)); 46 } catch (PackageParser.PackageParserException e) { 47 ... 48 } 49 try { 50 mInstallId = InstallEventReceiver 51 .addObserver(this, EventResultPersister.GENERATE_NEW_ID, 52 this::launchFinishBasedOnResult);//6 53 } catch (EventResultPersister.OutOfIdsException e) { 54 launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null); 55 } 56 try { 57 mSessionId = getPackageManager().getPackageInstaller().createSession(params);//7 58 } catch (IOException e) { 59 launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null); 60 } 61 } 62 ... 63 mSessionCallback = new InstallSessionCallback(); 64 } 65 }
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
1 @Override 2 protected void onResume() { 3 super.onResume(); 4 if (mInstallingTask == null) { 5 PackageInstaller installer = getPackageManager().getPackageInstaller(); 6 PackageInstaller.SessionInfo sessionInfo = installer.getSessionInfo(mSessionId);//1 7 if (sessionInfo != null && !sessionInfo.isActive()) {//2 8 mInstallingTask = new InstallingAsyncTask(); 9 mInstallingTask.execute(); 10 } else { 11 mCancelButton.setEnabled(false); 12 setFinishOnTouchOutside(false); 13 } 14 } 15 }
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
1 @Override 2 protected void onPostExecute(PackageInstaller.Session session) { 3 if (session != null) { 4 Intent broadcastIntent = new Intent(BROADCAST_ACTION); 5 broadcastIntent.setPackage( 6 getPackageManager().getPermissionControllerPackageName()); 7 broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId); 8 PendingIntent pendingIntent = PendingIntent.getBroadcast( 9 InstallInstalling.this, 10 mInstallId, 11 broadcastIntent, 12 PendingIntent.FLAG_UPDATE_CURRENT); 13 session.commit(pendingIntent.getIntentSender());//1 14 mCancelButton.setEnabled(false); 15 setFinishOnTouchOutside(false); 16 } else { 17 getPackageManager().getPackageInstaller().abandonSession(mSessionId); 18 if (!isCancelled()) { 19 launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null); 20 } 21 } 22 }
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
1 public void commit(@NonNull IntentSender statusReceiver) { 2 try { 3 mSession.commit(statusReceiver); 4 } catch (RemoteException e) { 5 throw e.rethrowFromSystemServer(); 6 } 7 }
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
1 @Override 2 public void commit(IntentSender statusReceiver) { 3 Preconditions.checkNotNull(statusReceiver); 4 ... 5 mActiveCount.incrementAndGet(); 6 final PackageInstallObserverAdapter adapter = new PackageInstallObserverAdapter(mContext, 7 statusReceiver, sessionId, mIsInstallerDeviceOwner, userId); 8 mHandler.obtainMessage(MSG_COMMIT, adapter.getBinder()).sendToTarget();//1 9 }
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
1 private final Handler.Callback mHandlerCallback = new Handler.Callback() { 2 @Override 3 public boolean handleMessage(Message msg) { 4 final PackageInfo pkgInfo = mPm.getPackageInfo( 5 params.appPackageName, PackageManager.GET_SIGNATURES 6 | PackageManager.MATCH_STATIC_SHARED_LIBRARIES /*flags*/, userId); 7 final ApplicationInfo appInfo = mPm.getApplicationInfo( 8 params.appPackageName, 0, userId); 9 synchronized (mLock) { 10 if (msg.obj != null) { 11 mRemoteObserver = (IPackageInstallObserver2) msg.obj;//1 12 } 13 try { 14 commitLocked(pkgInfo, appInfo);//2 15 } catch (PackageManagerException e) { 16 final String completeMsg = ExceptionUtils.getCompleteMessage(e); 17 Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg); 18 destroyInternal(); 19 dispatchSessionFinished(e.error, completeMsg, null);//3 20 } 21 return true; 22 } 23 } 24 };
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
1 private void commitLocked(PackageInfo pkgInfo, ApplicationInfo appInfo) 2 throws PackageManagerException { 3 ... 4 mPm.installStage(mPackageName, stageDir, stageCid, localObserver, params, 5 installerPackageName, installerUid, user, mCertificates); 6 }
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
1 private void dispatchSessionFinished(int returnCode, String msg, Bundle extras) { 2 mFinalStatus = returnCode; 3 mFinalMessage = msg; 4 if (mRemoteObserver != null) { 5 try { 6 mRemoteObserver.onPackageInstalled(mPackageName, returnCode, msg, extras);//1 7 } catch (RemoteException ignored) { 8 } 9 } 10 ... 11 }
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
1public class PackageInstallObserver { 2 private final IPackageInstallObserver2.Stub mBinder = new IPackageInstallObserver2.Stub() { 3 ... 4 @Override 5 public void onPackageInstalled(String basePackageName, int returnCode, 6 String msg, Bundle extras) { 7 PackageInstallObserver.this.onPackageInstalled(basePackageName, returnCode, msg, 8 extras);//1 9 } 10 };
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：
- 将APK的信息通过IO流的形式写入到PackageInstaller.Session中。
- 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。