开篇
PackageManagerService 系列文章如下（基于 Android 9.0 源码）
? ? ? ? ? ? ?核心源码
| 关键类 | 路径 |
|---|---|
| PackageInstaller.java | frameworks/base/core/java/android/content/pm/PackageInstaller.java |
| PackageInstallerActivity.java | packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java |
| InstallInstalling.java | packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java |
| PackageInstallerSession.java | frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java |
前言
在本系列上一篇文章中，我们学习了 PackageInstaller 是如何初始化的，这一篇文章我们继续学习 PackageInstaller 是如何安装 APK 的。
PackageInstallerActivity
在上一篇文章的末尾阶段，我们知道 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。
onClick
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(); // ? ? ? ? ? ? } } else { mScrollView.pageScroll(View.FOCUS_DOWN); } } } else if (v == mCancel) { // Cancel and finish setResult(RESULT_CANCELED); if (mSessionId != -1) { mInstaller.setPermissionsResult(mSessionId, false); } finish(); } } onClick 方法中分别对"确定"和"取消"按钮做了处理，主要查看对"确定"按钮的处理，我们发现调用了 startInstall 方法。
startInstall
private void startInstall() { // Start subactivity to actually install the application Intent newIntent = new Intent(); newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO, mPkgInfo.applicationInfo); newIntent.setData(mPackageURI); 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); /** * startInstall 方法用于跳转到 InstallInstalling 这个 Activity */ startActivity(newIntent); finish(); // 关闭当前的 PackageInstallerActivity } InstallInstalling
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。
onCreate
@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(); // 分别对 package 和 content 协议的 Uri 进行处理 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) { mSessionId = savedInstanceState.getInt(SESSION_ID); // mSessionId 是安装包的会话 id mInstallId = savedInstanceState.getInt(INSTALL_ID); // mInstallId 是等待的安装事件 id /** * 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) */ try { InstallEventReceiver.addObserver(this, mInstallId, this::launchFinishBasedOnResult); } catch (EventResultPersister.OutOfIdsException e) { // Does not happen } } else { // savedInstanceState 为 null PackageInstaller.SessionParams params = new PackageInstaller.SessionParams( PackageInstaller.SessionParams.MODE_FULL_INSTALL); 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()); try { PackageParser.PackageLite pkg = PackageParser.parsePackageLite(file, 0); params.setAppPackageName(pkg.packageName); params.setInstallLocation(pkg.installLocation); params.setSize( PackageHelper.calculateInstalledSize(pkg, false, params.abiOverride)); } catch (PackageParser.PackageParserException e) { Log.e(LOG_TAG, "Cannot parse package " + file + ". Assuming defaults."); Log.e(LOG_TAG, "Cannot calculate installed size " + file + ". Try only apk size."); params.setSize(file.length()); } catch (IOException e) { Log.e(LOG_TAG, "Cannot calculate installed size " + file + ". Try only apk size."); params.setSize(file.length()); } try { mInstallId = InstallEventReceiver .addObserver(this, EventResultPersister.GENERATE_NEW_ID, this::launchFinishBasedOnResult); } catch (EventResultPersister.OutOfIdsException e) { launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null); } try { mSessionId = getPackageManager().getPackageInstaller().createSession(params); } catch (IOException e) { launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null); } } ... ... mSessionCallback = new InstallSessionCallback(); } } onResume
我们查看 InstallInstalling 的 onResume 方法：
@Override protected void onResume() { super.onResume(); // This is the first onResume in a single life of the activity if (mInstallingTask == null) { PackageInstaller installer = getPackageManager().getPackageInstaller(); // 根据 mSessionId 得到 SessionInfo，SessionInfo 代表安装会话的详细信息 PackageInstaller.SessionInfo sessionInfo = installer.getSessionInfo(mSessionId); // 如果 sessionInfo 不为 Null 并且不是活动的，就创建并执行 InstallingAsyncTask if (sessionInfo != null && !sessionInfo.isActive()) { mInstallingTask = new InstallingAsyncTask(); // ? ? ? ? ? ? mInstallingTask.execute(); } else { // we will receive a broadcast when the install is finished mCancelButton.setEnabled(false); setFinishOnTouchOutside(false); } } } InstallingAsyncTask
既然启动了 InstallingAsyncTask，那我们就来看看 相关的 doInBackground 和 onPostExecute 方法：
/** * Send the package to the package installer and then register a event result observer that * will call {@link #launchFinishBasedOnResult(int, int, String)} */ private final class InstallingAsyncTask extends AsyncTask { volatile boolean isDone; // 根据包(APK)的 Uri，将 APK 的信息通过 IO 流的形式写入到 PackageInstaller.Session 中 @Override protected PackageInstaller.Session doInBackground(Void... params) { PackageInstaller.Session session; try { session = getPackageManager().getPackageInstaller().openSession(mSessionId); } catch (IOException e) { return null; } session.setStagingProgress(0); try { File file = new File(mPackageURI.getPath()); try (InputStream in = new FileInputStream(file)) { long sizeBytes = file.length(); try (OutputStream out = session .openWrite("PackageInstaller", 0, sizeBytes)) { byte[] buffer = new byte[1024 * 1024]; while (true) { int numRead = in.read(buffer); if (numRead == -1) { session.fsync(out); break; } if (isCancelled()) { session.close(); break; } out.write(buffer, 0, numRead); if (sizeBytes > 0) { float fraction = ((float) numRead / (float) sizeBytes); session.addProgress(fraction); } } } } return session; } catch (IOException | SecurityException e) { Log.e(LOG_TAG, "Could not write package", e); session.close(); return null; } finally { synchronized (this) { isDone = true; notifyAll(); } } } @Override protected void onPostExecute(PackageInstaller.Session session) { if (session != null) { Intent broadcastIntent = new Intent(BROADCAST_ACTION); broadcastIntent.setFlags(Intent.FLAG_RECEIVER_FOREGROUND); broadcastIntent.setPackage( getPackageManager().getPermissionControllerPackageName()); broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId); // 创建了一个 PendingIntent PendingIntent pendingIntent = PendingIntent.getBroadcast( InstallInstalling.this, mInstallId, broadcastIntent, PendingIntent.FLAG_UPDATE_CURRENT); /** * 将该 PendingIntent 的 IntentSender 通过 * PackageInstaller.Session 的 commit 方法发送出去 */ session.commit(pendingIntent.getIntentSender()); // ? ? ? ? ? ? mCancelButton.setEnabled(false); setFinishOnTouchOutside(false); } else { getPackageManager().getPackageInstaller().abandonSession(mSessionId); if (!isCancelled()) { launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null); } } } } Ok，问题来了，commit 到哪去了？我们不妨来看一下 PackageInstaller.Session 的 commit 方法：
commit
public void commit(@NonNull IntentSender statusReceiver) { try { mSession.commit(statusReceiver, false); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } mSession
public static class Session implements Closeable { private IPackageInstallerSession mSession; 我们发现，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，又回到框架层处理了。
PackageInstallerSession
commit
@Override public void commit(@NonNull IntentSender statusReceiver, boolean forTransfer) { Preconditions.checkNotNull(statusReceiver); final boolean wasSealed; synchronized (mLock) { assertCallerIsOwnerOrRootLocked(); assertPreparedAndNotDestroyedLocked("commit"); // 将包的信息封装为 PackageInstallObserverAdapter final PackageInstallObserverAdapter adapter = new PackageInstallObserverAdapter( mContext, statusReceiver, sessionId, isInstallerDeviceOwnerLocked(), userId); mRemoteObserver = adapter.getBinder(); ... ... mHandler.obtainMessage(MSG_COMMIT).sendToTarget(); // ? ? ? ? ? ? } ... ... } Handler.Callback
private final Handler.Callback mHandlerCallback = new Handler.Callback() { @Override public boolean handleMessage(Message msg) { switch (msg.what) { case MSG_COMMIT: synchronized (mLock) { try { commitLocked(); // ? ? ? ? ? ? } catch (PackageManagerException e) { final String completeMsg = ExceptionUtils.getCompleteMessage(e); Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg); destroyInternal(); dispatchSessionFinished(e.error, completeMsg, null); // ? ? ? ? ? ? } } break; case MSG_SESSION_FINISHED_WITH_EXCEPTION: PackageManagerException e = (PackageManagerException) msg.obj; dispatchSessionFinished(e.error, ExceptionUtils.getCompleteMessage(e), null); break; } return true; } }; commitLocked
private final PackageManagerService mPm; private void commitLocked() throws PackageManagerException { ... ... /** * commitLocked 方法很长，我们主要关注这一行代码 * 调用 PackageManagerService 的 installStage 方法 * 这样安装 APK 的代码逻辑就进入了 PackageManagerService 中 */ mPm.installStage(mPackageName, stageDir, stageCid, localObserver, params, mInstallerPackageName, mInstallerUid, user, mCertificates); } dispatchSessionFinished
我们这边再看一下，如果 commitLocked 出现了异常后的流程处理：
private void dispatchSessionFinished(int returnCode, String msg, Bundle extras) { final IPackageInstallObserver2 observer; final String packageName; ... ... if (observer != null) { try { // 调用 IPackageInstallObserver2 的 onPackageInstalled 方法 observer.onPackageInstalled(packageName, returnCode, msg, extras); // ? ? ? ? ? ? } catch (RemoteException ignored) { } } ... ... mCallback.onSessionFinished(this, success); } 它的实现方法在 PackageInstallObserver 类中：
public class PackageInstallObserver { private final IPackageInstallObserver2.Stub mBinder = new IPackageInstallObserver2.Stub() { @Override public void onUserActionRequired(Intent intent) { PackageInstallObserver.this.onUserActionRequired(intent); } @Override public void onPackageInstalled(String basePackageName, int returnCode, String msg, Bundle extras) { /** * 调用了 PackageInstallObserver 的 onPackageInstalled 方法 * 实现这个方法的类为 PackageInstallObserver 的子类：PackageInstallObserverAdapter */ PackageInstallObserver.this.onPackageInstalled(basePackageName, returnCode, msg, extras); } }; ... ...} 也就是说：dispatchSessionFinished 方法会通过 Observer 的 onPackageInstalled 方法，将出现的 PackageManagerException 异常信息回调给 PackageInstallObserverAdapter。
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。参考
01.