Android包管理机制（二）PackageInstaller安装APK

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

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();        }    }复制代码

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();    }复制代码

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();        }    }复制代码

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);            }        }    }复制代码

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);                }            }        }复制代码

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();            }        }复制代码

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    }复制代码

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;            }        }    };复制代码

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);    }复制代码

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) {            }        }        ...    }复制代码

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        }    };复制代码

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。

前言

1.PackageInstaller中的处理

2.Java框架层的处理

3.总结

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