Apk安装之——点击安装确认页面的确认按钮，到将安装过程交给PMS的过程分析

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我是靠谱客的博主直率方盒，最近开发中收集的这篇文章主要介绍Apk安装之——点击安装确认页面的确认按钮，到将安装过程交给PMS的过程分析，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

上篇文章Apk安装之——安装确认页面的初始化，讲解了apk包安装的一个小的阶段，展示安装确认页面的过程。这篇文章，继续分析，点击这个页面的确定按钮，开始安装apk的过程。下面是触发点击事件的具体代码：

http://androidxref.com/9.0.0_r3/xref/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();
}
} else {
mScrollView.pageScroll(View.FOCUS_DOWN);
}
}
} else if (v == mCancel) {
// Cancel and finish
setResult(RESULT_CANCELED);
if (mSessionId != -1) {
mInstaller.setPermissionsResult(mSessionId, false);
}
finish();
}
}

点击确认按钮，只要mSessionId的值不是-1，就会执行，startInstall()方法进行apk的安装。

http://androidxref.com/9.0.0_r3/xref/packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java
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);
//关键代码
newIntent.setClass(this, InstallInstalling.class);
...
newIntent.addFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI);
startActivity(newIntent);
finish();
}

这个方法内部，会跳转到InstallInstalling这个Activity中，并关闭当前的PackageInstallerActivity页面。下面看看InstallInstalling这个类的onCreate方法：

http://androidxref.com/9.0.0_r3/xref/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 {
//关键代码1
final File sourceFile = new File(mPackageURI.getPath());
PackageUtil.initSnippetForNewApp(this, PackageUtil.getAppSnippet(this, appInfo,
sourceFile), R.id.app_snippet);
//关键代码2
if (savedInstanceState != null) {
mSessionId = savedInstanceState.getInt(SESSION_ID);
mInstallId = savedInstanceState.getInt(INSTALL_ID);
// Reregister for result; might instantly call back if result was delivered while
// activity was destroyed
try {
//关键代码3
InstallEventReceiver.addObserver(this, mInstallId,
this::launchFinishBasedOnResult);
} catch (EventResultPersister.OutOfIdsException e) {
// Does not happen
}
} else {
//关键代码4
PackageInstaller.SessionParams params = new PackageInstaller.SessionParams(
PackageInstaller.SessionParams.MODE_FULL_INSTALL);
params.installFlags = PackageManager.INSTALL_FULL_APP;
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);
File file = new File(mPackageURI.getPath());
try {
//关键代码5
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 {
//关键代码6
mInstallId = InstallEventReceiver
.addObserver(this, EventResultPersister.GENERATE_NEW_ID,
this::launchFinishBasedOnResult);
} catch (EventResultPersister.OutOfIdsException e) {
launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
}
try {
//关键代码7
mSessionId = getPackageManager().getPackageInstaller().createSession(params);
} catch (IOException e) {
launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
}
}
mCancelButton = (Button) findViewById(R.id.cancel_button);
mCancelButton.setOnClickListener(view -> {
if (mInstallingTask != null) {
mInstallingTask.cancel(true);
}
if (mSessionId > 0) {
getPackageManager().getPackageInstaller().abandonSession(mSessionId);
mSessionId = 0;
}
setResult(RESULT_CANCELED);
finish();
});
mSessionCallback = new InstallSessionCallback();
}
}

这个方法内部，首先根据是content协议还是package协议，来进行不同的处理，本案例是已content协议启动apk的安装流程的，所以会执行关键代码1处的代码，这里会判断savedInstanceState如果不为null，则会取出保存的sessionId和installId，sessionId表示此次安装的会话，installId表示等待安装事件id，在关键代码3处，并给InstallEventReceiver添加一个观察者，回调时，观察者的launchFinishBasedOnResult方法会执行。如果savedInstanceState为null,在关键代码4处，会创建PackageInstaller.SessionParams对象，并给这个对象的各个字段赋值。在关键代码5处，调用PackageParser.parsePackageLite方法，解析apk文件，这里是对apk进行轻量解析，主要是获取apk的包名，apk的位置，以及apk的大小等信息，保存到PackageParser.PackageLite类型的对象pkg中。关键代码6处，也是给InstallEventReceiver添加一个观察者，并返回一个installId,关键代码7处，会创建一个sessionId。以上便是InstallInstalling的onCreate方法的分析。下面接着看这个类的onResume方法：

http://androidxref.com/9.0.0_r3/xref/packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java
@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();
PackageInstaller.SessionInfo sessionInfo = installer.getSessionInfo(mSessionId);
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);
}
}
}

这个方法中，如果sessionInfo不会null，并且sessionInfo是非活动的，则会创建一个InstallingAsyncTask()，并执行这个asynTask。下面看看这个InstallingAsyncTask()具体做了什么：

http://androidxref.com/9.0.0_r3/xref/packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallInstalling.java
private final class InstallingAsyncTask extends AsyncTask<Void, Void,
PackageInstaller.Session> {
volatile boolean isDone;
@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);
PendingIntent pendingIntent = PendingIntent.getBroadcast(
InstallInstalling.this,
mInstallId,
broadcastIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
//关键代码
session.commit(pendingIntent.getIntentSender());
mCancelButton.setEnabled(false);
setFinishOnTouchOutside(false);
} else {
getPackageManager().getPackageInstaller().abandonSession(mSessionId);
if (!isCancelled()) {
launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
}
}
}
}

这个InstallingAsyncTask的doInBackground方法内部，将apk文件写入到了PackageInstaller.Session类型的对象session中，在onPostExecute方法中，执行PackageInstaller.Session的commit方法。

http://androidxref.com/9.0.0_r3/xref/frameworks/base/core/java/android/content/pm/PackageInstaller.java
public void commit(@NonNull IntentSender statusReceiver) {
try {
mSession.commit(statusReceiver, false);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}

这个方法内部会调用mSession的commit方法，mSession是IPackageInstallerSession类型的，IPackageInstallerSession其实是system_servier进程的PackageInstallerSession在客户端的一个代理对象。mSession。commit方法，其实就是发起了进程间的通信，system_servier进程的PackageInstallerSession的commit方法会执行这个请求。下面看看这个方法的具体实现：

http://androidxref.com/9.0.0_r3/xref/frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java
@Override
public void commit(@NonNull IntentSender statusReceiver, boolean forTransfer) {
Preconditions.checkNotNull(statusReceiver);
final boolean wasSealed;
synchronized (mLock) {
...
mHandler.obtainMessage(MSG_COMMIT).sendToTarget();
}
...
}
private final Handler.Callback mHandlerCallback = new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {
switch (msg.what) {
...
case MSG_COMMIT:
synchronized (mLock) {
try {
//关键代码
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_ON_PACKAGE_INSTALLED:
...
break;
}
return true;
}
}

这个方法内部，会通过handler发送一个MSG_COMMIT消息，使得handler中的commitLocked()方法得到执行。下面看看这个方法：

@GuardedBy("mLock")
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();
dispatchSessionFinished(returnCode, msg, extras);
}
};
final UserHandle user;
if ((params.installFlags & PackageManager.INSTALL_ALL_USERS) != 0) {
user = UserHandle.ALL;
} else {
user = new UserHandle(userId);
}
mRelinquished = true;
//关键代码
mPm.installStage(mPackageName, stageDir, localObserver, params,
mInstallerPackageName, mInstallerUid, user, mSigningDetails);
}

这个方法内部，主要是执行mPm的installStage方法，前面的很多代码都是为这个方法的创建很多的参数。这个mPm是PackageManagerService类型的，其实这里的安装，交给了PackageManagerService来完成。

总结：点击安装确认页面的确定按钮后，会创建安装会话id，和准备安装的事件id,接着会将apk文件读取到PackageInstaller.Session类型的对象中，在调用这PackageInstaller.Session类型的对象的commit方法，将具体的安装交给PMS。

参考：Android包管理机制（二）PackageInstaller安装APK