前言
在本系列上一篇文章Android9.0 PM机制系列（一）PackageInstaller初始化解析中我们学习了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Android9.0。
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) { //初始化时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：
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.installFlags = PackageManager.INSTALL_FULL_APP; //9.0新增
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);
params.installerPackageName =
getIntent().getStringExtra(Intent.EXTRA_INSTALLER_PACKAGE_NAME);//9.0新增
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。
- 只要mInstallId 或者mSessionId 创建失败就会调出安装失败界面。
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
private final class InstallingAsyncTask extends AsyncTask<Void, Void,
327 PackageInstaller.Session> {
328 volatile boolean isDone;
329
330 @Override
331 protected PackageInstaller.Session doInBackground(Void... params) {
332 PackageInstaller.Session session;
333 try {
334 session = getPackageManager().getPackageInstaller().openSession(mSessionId);
335 } catch (IOException e) {
336 return null;
337 }
338
339 session.setStagingProgress(0);
340
341 try {
342 File file = new File(mPackageURI.getPath());
343
344 try (InputStream in = new FileInputStream(file)) {
345 long sizeBytes = file.length();
346 try (OutputStream out = session
347 .openWrite("PackageInstaller", 0, sizeBytes)) {
//8.0 是 byte[] buffer = new byte[4096];
348 byte[] buffer = new byte[1024 * 1024];
349 while (true) {
350 int numRead = in.read(buffer);
351
352 if (numRead == -1) {
353 session.fsync(out);
354 break;
355 }
356
357 if (isCancelled()) {
358 session.close();
359 break;
360 }
361
362 out.write(buffer, 0, numRead);
363 if (sizeBytes > 0) {
364 float fraction = ((float) numRead / (float) sizeBytes);
365 session.addProgress(fraction);
366 }
367 }
368 }
369 }
370
371 return session;
372 } catch (IOException | SecurityException e) {
373 Log.e(LOG_TAG, "Could not write package", e);
374
375 session.close();
376
377 return null;
378 } finally {
379 synchronized (this) {
380 isDone = true;
381 notifyAll();
382 }
383 }
384 }
385
386 @Override
387 protected void onPostExecute(PackageInstaller.Session session) {
388 if (session != null) {
389 Intent broadcastIntent = new Intent(BROADCAST_ACTION);
/*9.0新增这行，AMS构造方法中构造了两个队列，一个前台队列，一个后台队列。结合其构造方法可知，
两者区别在于一个是设置的广播超时时间不同，前台是10s，后台是60s，另外一个是是否要等待后台服务处理完，
前台广播是不用等待的，后台广播需要等待。
想要让广播能放到前台队列中，只需调用Intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND)即可
*/
390 broadcastIntent.setFlags(Intent.FLAG_RECEIVER_FOREGROUND);
391 broadcastIntent.setPackage(
392 getPackageManager().getPermissionControllerPackageName());
393 broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId);
394
395 PendingIntent pendingIntent = PendingIntent.getBroadcast(
396 InstallInstalling.this,
397 mInstallId,
398 broadcastIntent,
399 PendingIntent.FLAG_UPDATE_CURRENT);
400
401 session.commit(pendingIntent.getIntentSender());
402 mCancelButton.setEnabled(false);
403 setFinishOnTouchOutside(false);
404 } else {
405 getPackageManager().getPackageInstaller().abandonSession(mSessionId);
406
407 if (!isCancelled()) {
408 launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
409 }
410 }
411 }
412 }```
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**
```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);
/*8.0 : mHandler.obtainMessage(MSG_COMMIT, adapter.getBinder()).sendToTarget();
在Handler处理的时候才对mRemoteObserver进行赋值
9.0 直接在这里对mRemoteObserver进行赋值
*/
mRemoteObserver = adapter.getBinder();
if (!mSealed) {
try {
//验证apk有效性，并给pkgInfo appInfo 赋值等，8.0是放到Handler处理的
sealAndValidateLocked();
} catch (IOException e) {
...
}
}
mHandler.obtainMessage(MSG_COMMIT).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) {
switch (msg.what) {
case MSG_COMMIT:
synchronized (mLock) {
try {
commitLocked();//1
} catch (PackageManagerException e) {
final String completeMsg = ExceptionUtils.getCompleteMessage(e);
Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg);
destroyInternal();
dispatchSessionFinished(e.error, completeMsg, null);//2
}
}
break;
case MSG_ON_PACKAGE_INSTALLED:
final SomeArgs args = (SomeArgs) msg.obj;
final String packageName = (String) args.arg1;
final String message = (String) args.arg2;
final Bundle extras = (Bundle) args.arg3;
final IPackageInstallObserver2 observer = (IPackageInstallObserver2) args.arg4;
final int returnCode = args.argi1;
args.recycle();
try {
observer.onPackageInstalled(packageName, returnCode, message, extras);
} catch (RemoteException ignored) {
}
break;
}
};注释1处的commitLocked方法如下所示。
private void commitLocked()
throws PackageManagerException {
...
// We've reached point of no return; call into PMS to install the stage.
// Regardless of success or failure we always destroy session.
final IPackageInstallObserver2 localObserver = new IPackageInstallObserver2.Stub() {
@Override
public void onUserActionRequired(Intent intent) {
throw new IllegalStateException();
}
@Override
public void onPackageInstalled(String basePackageName, int returnCode, String msg,
Bundle extras) {
destroyInternal();
//安装完毕后的回调，很多地方都会调这个方法！然后会一直回调到最开始处，然后发广播给客户端
dispatchSessionFinished(returnCode, msg, extras);//2
}
};
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。
在Android 9.0 PM机制系列（三）PMS处理APK的安装文章中说到，如果安装完成，就会调用到注释2处。
同样，回到mHandlerCallback的handleMessage方法，如果commitLocked方法出现PackageManagerException异常，就会调用注释2处的dispatchSessionFinished方法。
同理，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) {
1546 final IPackageInstallObserver2 observer;
1547 final String packageName;
1548 synchronized (mLock) {
1549 mFinalStatus = returnCode;
1550 mFinalMessage = msg;
1551
1552 observer = mRemoteObserver;
1553 packageName = mPackageName;
1554 }
1555
1556 if (observer != null) {
1557 // Execute observer.onPackageInstalled on different tread as we don't want callers
1558 // inside the system server have to worry about catching the callbacks while they are
1559 // calling into the session
1560 final SomeArgs args = SomeArgs.obtain();
1561 args.arg1 = packageName;
1562 args.arg2 = msg;
1563 args.arg3 = extras;
1564 args.arg4 = observer;
1565 args.argi1 = returnCode;
1566
1567 mHandler.obtainMessage(MSG_ON_PACKAGE_INSTALLED, args).sendToTarget();//1
1568 }
1569
1570 final boolean success = (returnCode == PackageManager.INSTALL_SUCCEEDED);
1571
1572 // Send broadcast to default launcher only if it's a new install
1573 final boolean isNewInstall = extras == null || !extras.getBoolean(Intent.EXTRA_REPLACING);
1574 if (success && isNewInstall) {
1575 mPm.sendSessionCommitBroadcast(generateInfo(), userId);
1576 }
1577
1578 mCallback.onSessionFinished(this, success);
1579 }注释1处最终会调用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
}
};
public IPackageInstallObserver2 getBinder() {
return mBinder;
}
}- 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。
/frameworks/base/services/core/java/com/android/server/pm/PackageInstallerService.java
static class PackageInstallObserverAdapter extends PackageInstallObserver {
private final Context mContext;
private final IntentSender mTarget;
private final int mSessionId;
private final boolean mShowNotification;
private final int mUserId;
public PackageInstallObserverAdapter(Context context, IntentSender target, int sessionId,
boolean showNotification, int userId) {
mContext = context;
mTarget = target;
mSessionId = sessionId;
mShowNotification = showNotification;
mUserId = userId;
}
...
@Override
public void onPackageInstalled(String basePackageName, int returnCode, String msg,
Bundle extras) {
if (PackageManager.INSTALL_SUCCEEDED == returnCode && mShowNotification) {
boolean update = (extras != null) && extras.getBoolean(Intent.EXTRA_REPLACING);
Notification notification = buildSuccessNotification(mContext,
mContext.getResources()
.getString(update ? R.string.package_updated_device_owner :
R.string.package_installed_device_owner),
basePackageName,
mUserId);
if (notification != null) {
NotificationManager notificationManager = (NotificationManager)
mContext.getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(basePackageName,
SystemMessage.NOTE_PACKAGE_STATE,
notification);
}
}
final Intent fillIn = new Intent();
fillIn.putExtra(PackageInstaller.EXTRA_PACKAGE_NAME, basePackageName);
fillIn.putExtra(PackageInstaller.EXTRA_SESSION_ID, mSessionId);
fillIn.putExtra(PackageInstaller.EXTRA_STATUS,
PackageManager.installStatusToPublicStatus(returnCode));
fillIn.putExtra(PackageInstaller.EXTRA_STATUS_MESSAGE,
PackageManager.installStatusToString(returnCode, msg));
fillIn.putExtra(PackageInstaller.EXTRA_LEGACY_STATUS, returnCode);
if (extras != null) {
final String existing = extras.getString(
PackageManager.EXTRA_FAILURE_EXISTING_PACKAGE);
if (!TextUtils.isEmpty(existing)) {
fillIn.putExtra(PackageInstaller.EXTRA_OTHER_PACKAGE_NAME, existing);
}
}
try {
mTarget.sendIntent(mContext, 0, fillIn, null, null); //1
} catch (SendIntentException ignored) {
}
}
}最终回调到应用层接受广播和安装的结果。
- 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。
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
