Android包管理機制（二）PackageInstaller安裝APK

時間  2019-11-24
標籤 android 包管 機制 packageinstaller 安裝 apk 欄目 Android 简体版
原文   原文鏈接

前言

在本系列上一篇文章Android包管理機制（一）PackageInstaller的初始化中咱們學習了PackageInstaller是如何初始化的，這一篇文章咱們接着學習PackageInstaller是如何安裝APK的。本系列文章的源碼基於Android8.0。html

1.PackageInstaller中的處理

緊接着上一篇的內容，在PackageInstallerActivity調用startInstallConfirm方法初始化安裝確認界面後，這個安裝確認界面就會呈現給用戶，用戶若是想要安裝這個應用程序就會點擊肯定按鈕，就會調用PackageInstallerActivity的onClick方法，以下所示。 packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.javajava

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();
        }
    }
複製代碼

onClick方法中分別對肯定和取消按鈕作處理，主要查看對肯定按鈕的處理，註釋1處調用了startInstall方法： packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.javaandroid

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();
    }
複製代碼

startInstall方法用於跳轉到InstallInstalling這個Activity，並關閉掉當前的PackageInstallerActivity。InstallInstalling主要用於向包管理器發送包的信息並處理包管理的回調。 InstallInstalling的onCreate方法以下所示。 packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.javasession

@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 {
        //根據mPackageURI建立一個對應的File 
            final File sourceFile = new File(mPackageURI.getPath());
            PackageUtil.initSnippetForNewApp(this, PackageUtil.getAppSnippet(this, appInfo,
                    sourceFile), R.id.app_snippet);
            //若是savedInstanceState不爲null，獲取此前保存的mSessionId和mInstallId 
            if (savedInstanceState != null) {//1
                mSessionId = savedInstanceState.getInt(SESSION_ID);
                mInstallId = savedInstanceState.getInt(INSTALL_ID);
              //向InstallEventReceiver註冊一個觀察者
                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();
        }
    }
複製代碼

onCreate方法中會分別對package和content協議的Uri進行處理，咱們來看content協議的Uri處理部分。註釋1處若是savedInstanceState不爲null，獲取此前保存的mSessionId和mInstallId，其中mSessionId是安裝包的會話id，mInstallId是等待的安裝事件id。註釋2處根據mInstallId向InstallEventReceiver註冊一個觀察者，launchFinishBasedOnResult會接收到安裝事件的回調，不管安裝成功或者失敗都會關閉當前的Activity(InstallInstalling)。若是savedInstanceState爲null，代碼的邏輯也是相似的，註釋3處建立SessionParams，它用來表明安裝會話的參數，註釋四、5處根據mPackageUri對包（APK）進行輕量級的解析，並將解析的參數賦值給SessionParams。註釋6處和註釋2處相似向InstallEventReceiver註冊一個觀察者返回一個新的mInstallId，其中InstallEventReceiver繼承自BroadcastReceiver，用於接收安裝事件並回調給EventResultPersister。 註釋7處PackageInstaller的createSession方法內部會經過IPackageInstaller與PackageInstallerService進行進程間通訊，最終調用的是PackageInstallerService的createSession方法來建立並返回mSessionId。 InstallInstalling的onCreate方法就分析到這，接着查看InstallInstalling的onResume方法： packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.javaapp

@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);
            }
        }
    }
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註釋1處根據mSessionId獲得SessionInfo，SessionInfo表明安裝會話的詳細信息。註釋2處若是sessionInfo不爲Null而且不是活動的，就建立並執行InstallingAsyncTask。InstallingAsyncTask的doInBackground方法中會根據包(APK)的Uri，將APK的信息經過IO流的形式寫入到PackageInstaller.Session中。InstallingAsyncTask的onPostExecute方法以下所示。 packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java框架

@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);
                }
            }
        }
複製代碼

建立了一個PendingIntent，並將該PendingIntent的IntentSender經過註釋1處的PackageInstaller.Session的commit方法發送出去，發送去哪了呢？接着查看PackageInstaller.Session的commit方法。 frameworks/base/core/java/android/content/pm/PackageInstaller.javaide

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

mSession的類型爲IPackageInstallerSession，這說明要經過IPackageInstallerSession來進行進程間的通訊，最終會調用PackageInstallerSession的commit方法，這樣代碼邏輯就到了Java框架層的。學習

2.Java框架層的處理

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

@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
    }
複製代碼

commit方法中會將包的信息封裝爲PackageInstallObserverAdapter ，它在PMS中被定義。在註釋1處會向Handler發送一個類型爲MSG_COMMIT的消息，其中adapter.getBinder()會獲得IPackageInstallObserver2.Stub類型的觀察者，從類型就知道這個觀察者是能夠跨進程進行回調的。處理該消息的代碼以下所示。 frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.javaspa

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;
            }
        }
    };
複製代碼

註釋1處獲取IPackageInstallObserver2類型的觀察者mRemoteObserver，註釋2處的commitLocked方法以下所示。 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);
    }
複製代碼

commitLocked方法比較長，這裏截取最主要的信息，會調用PMS的installStage方法，這樣代碼邏輯就進入了PMS中。 回到mHandlerCallback的handleMessage方法，若是commitLocked方法出現PackageManagerException異常，就會調用註釋3處的dispatchSessionFinished方法，它的實現以下所示： 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) {
            }
        }
        ...
    }
複製代碼

註釋1處會調用IPackageInstallObserver2的onPackageInstalled方法，具體是實如今PackageInstallObserver類中： 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
        }
    };
複製代碼

註釋1處調用了PackageInstallObserver的onPackageInstalled方法，實現這個方法的類爲PackageInstallObserver的子類、前面提到的PackageInstallObserverAdapter。總結一下就是dispatchSessionFinished方法會經過mRemoteObserver的onPackageInstalled方法，將Complete方法出現的PackageManagerException的異常信息回調給PackageInstallObserverAdapter。

3.總結

本篇文章講解了PackageInstaller安裝APK的過程，簡單來講就兩步：

  1. 將APK的信息經過IO流的形式寫入到PackageInstaller.Session中。
  2. 調用PackageInstaller.Session的commit方法，將APK的信息交由PMS處理。

因爲PMS中對APK安裝的處理比較複雜，所以關於PMS的處理部分會在本系列的下一篇文章進行講解。

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