Android通过PackageManagerService（后面简称Pms）进行包管理，其主要功能包括：用户ID分配、包解析、包的安装卸载等。本文不对Pms进行分析，主要目的是探讨一下包安装。在本文中主要探讨包安装的相关操作，卸载作为安装的逆过程，实现类似，不再赘述。
Android中APK的安装方式
在Android中APK的安装有三种方式：
1、开机Pms初始化时，扫描包安装目录。
@/frameworks/base/services/java/com/android/server/SystemServer.java
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public void initAndLoop() {
......
IPackageManager pm = null;
......
try {
......
pm = PackageManagerService.main(context, installer,
factoryTest != SystemServer.FACTORY_TEST_OFF,
onlyCore);
......
} catch (RuntimeException e) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting core service", e);
}
......
}
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@/frameworks/base/services/java/com/android/server/pm/PackageManagerService.java
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public static final IPackageManager main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
ServiceManager.addService("package", m);
return m;
}
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下面是Pms构造函数的实现：
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public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
......
synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
......
File dataDir = Environment.getDataDirectory();
mAppDataDir = new File(dataDir, "data");
mAppInstallDir = new File(dataDir, "app");
mAppLibInstallDir = new File(dataDir, "app-lib");
mAsecInternalPath = new File(dataDir, "app-asec").getPath();
mUserAppDataDir = new File(dataDir, "user");
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
......
// Find base frameworks (resource packages without code).
mFrameworkInstallObserver = new AppDirObserver(
frameworkDir.getPath(), OBSERVER_EVENTS, true, false);
mFrameworkInstallObserver.startWatching();
scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR,
scanMode | SCAN_NO_DEX, 0);
// Collected privileged system packages.
File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
mPrivilegedInstallObserver = new AppDirObserver(
privilegedAppDir.getPath(), OBSERVER_EVENTS, true, true);
mPrivilegedInstallObserver.startWatching();
scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED, scanMode, 0);
// Collect ordinary system packages.
File systemAppDir = new File(Environment.getRootDirectory(), "app");
mSystemInstallObserver = new AppDirObserver(
systemAppDir.getPath(), OBSERVER_EVENTS, true, false);
mSystemInstallObserver.startWatching();
scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
// Collect all vendor packages.
File vendorAppDir = new File("/vendor/app");
mVendorInstallObserver = new AppDirObserver(
vendorAppDir.getPath(), OBSERVER_EVENTS, true, false);
mVendorInstallObserver.startWatching();
scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
......
if (!mOnlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
mAppInstallObserver = new AppDirObserver(
mAppInstallDir.getPath(), OBSERVER_EVENTS, false, false);
mAppInstallObserver.startWatching();
scanDirLI(mAppInstallDir, 0, scanMode, 0);
mDrmAppInstallObserver = new AppDirObserver(
mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false, false);
mDrmAppInstallObserver.startWatching();
scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
scanMode, 0);
......
} // synchronized (mPackages)
} // synchronized (mInstallLock)
}
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通过Pms的构造函数可以看出，Pms在初始化时会扫描/system/app、vender/app、/data/app、/data/app-private四个应用安装目录，然后调用sanDirLI方法进行安装。Pms通过AppDirObserver对这四个应用安装目录进行监控，一旦发现APK格式的文件则会调用scanPackageLI进行安装。
2、通过包安装器PackageInstaller安装
Android提供了一个默认的包安装器，位于/package/app/PackageInstaller目录。通过其Manifest文件可以看出，PackageInstaller会对我们安装应用发出的Intent进行处理，这里PackageInstaller提供了两种处理方式，分别是：file方式和package方式。
@/package/app/PackageInstaller/AndroidManifest.xml
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<activity android:name=".PackageInstallerActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:excludeFromRecents="true">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.INSTALL_PACKAGE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="file" />
<data android:mimeType="application/vnd.android.package-archive" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.INSTALL_PACKAGE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="file" />
<data android:scheme="package" />
</intent-filter>
</activity>
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@/package/app/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java
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@Override
protected void onCreate(Bundle icicle) {
super.onCreate(icicle);
......
initiateInstall();
}
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private void initiateInstall() {
......
startInstallConfirm();
}
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在startInstallConfirm方法中点击“确认”后，会发出一个Intent，接收者为InstallAppProgress。
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public void onClick(View v) {
if(v == mOk) {
if (mOkCanInstall || mScrollView == null) {
// Start subactivity to actually install the application
mInstallFlowAnalytics.setInstallButtonClicked();
Intent newIntent = new Intent();
newIntent.putExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO,
mPkgInfo.applicationInfo);
newIntent.setData(mPackageURI);
newIntent.setClass(this, InstallAppProgress.class);
......
startActivity(newIntent);
finish();
} else {
mScrollView.pageScroll(View.FOCUS_DOWN);
}
} else if(v == mCancel) {
......
}
}
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@/package/app/PackageInstaller/src/com/android/packageinstaller/InstallAppProgress.java
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public void initView() {
setContentView(R.layout.op_progress);
int installFlags = 0;
PackageManager pm = getPackageManager();
......
String installerPackageName = getIntent().getStringExtra(
Intent.EXTRA_INSTALLER_PACKAGE_NAME);
Uri originatingURI = getIntent().getParcelableExtra(Intent.EXTRA_ORIGINATING_URI);
Uri referrer = getIntent().getParcelableExtra(Intent.EXTRA_REFERRER);
int originatingUid = getIntent().getIntExtra(Intent.EXTRA_ORIGINATING_UID,
VerificationParams.NO_UID);
ManifestDigest manifestDigest = getIntent().getParcelableExtra(EXTRA_MANIFEST_DIGEST);
VerificationParams verificationParams = new VerificationParams(null, originatingURI,
referrer, originatingUid, manifestDigest);
PackageInstallObserver observer = new PackageInstallObserver();
if ("package".equals(mPackageURI.getScheme())) {
try {
pm.installExistingPackage(mAppInfo.packageName);
observer.packageInstalled(mAppInfo.packageName,
PackageManager.INSTALL_SUCCEEDED);
} catch (PackageManager.NameNotFoundException e) {
observer.packageInstalled(mAppInfo.packageName,
PackageManager.INSTALL_FAILED_INVALID_APK);
}
} else {
pm.installPackageWithVerificationAndEncryption(mPackageURI, observer, installFlags,
installerPackageName, verificationParams, null);
}
}
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InstallAppProgress即应用安装过程中的进度条界面。通过上面的代码可以看到在initView方法的最后会调用Pms的installPackageWithVerificationAndEncryption方法进行安装。
3、通过adb命令安装
adb命令pm是Pms的Shell客户端，通过pm可以进行包相关的一些操作，包括安装和卸载。pm命令的用法如下：
pm的代码实现在Pm.java中，如下：
@/frameworks/base/cmds/pm/src/com/android/commands/pm/Pm.java
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public static void main(String[] args) {
new Pm().run(args);
}
public void run(String[] args) {
......
mPm = IPackageManager.Stub.asInterface(ServiceManager.getService("package"));
......
if ("install".equals(op)) {
runInstall();
return;
}
if ("uninstall".equals(op)) {
runUninstall();
return;
}
......
}
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在run方法中初始化了一个Pms的客户端代理对象mPm，后续的相关操作将有mPm完成。下面看一下Pm中负责安装的方法runInstall的代码实现：
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private void runInstall() {
int installFlags = PackageManager.INSTALL_ALL_USERS;
......
while ((opt=nextOption()) != null) {
if (opt.equals("-l")) {
installFlags |= PackageManager.INSTALL_FORWARD_LOCK;
} else if (opt.equals("-r")) {
installFlags |= PackageManager.INSTALL_REPLACE_EXISTING;
} else if (opt.equals("-i")) {
installerPackageName = nextOptionData();
if (installerPackageName == null) {
System.err.println("Error: no value specified for -i");
return;
}
} else if (opt.equals("-t")) {
installFlags |= PackageManager.INSTALL_ALLOW_TEST;
} else if (opt.equals("-s")) {
// Override if -s option is specified.
installFlags |= PackageManager.INSTALL_EXTERNAL;
} else if (opt.equals("-f")) {
// Override if -s option is specified.
installFlags |= PackageManager.INSTALL_INTERNAL;
} else if (opt.equals("-d")) {
installFlags |= PackageManager.INSTALL_ALLOW_DOWNGRADE;
......
PackageInstallObserver obs = new PackageInstallObserver();
try {
VerificationParams verificationParams = new VerificationParams(verificationURI,
originatingURI, referrerURI, VerificationParams.NO_UID, null);
mPm.installPackageWithVerificationAndEncryption(apkURI, obs, installFlags,
installerPackageName, verificationParams, encryptionParams);
synchronized (obs) {
while (!obs.finished) {
try {
obs.wait();
} catch (InterruptedException e) {
}
}
if (obs.result == PackageManager.INSTALL_SUCCEEDED) {
System.out.println("Success");
} else {
System.err.println("Failure ["
+ installFailureToString(obs.result)
+ "]");
}
}
} catch (RemoteException e) {
System.err.println(e.toString());
System.err.println(PM_NOT_RUNNING_ERR);
}
}
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可以看出runInstall最终会调用Pms的installPackageWithVerificationAndEncryption方法进行安装。通过pm安装时，安装成功的返回信息为“Success”，安装失败的返回信息为”Failure[失败信息]"。
静默安装实现
在了解了Android中包安装的方式后，接下来探讨一些如何实现”静默安装“。所谓静默安装即跳过安装界面和进度条，在不被用户察觉的情况下载后台安装。下面针对上面的三种安装方式分别来分析如何实现静默安装。
1、push安装包到应用安装目录的方式
在Pms初始化时安装包的流程中，我们知道Pms会监控/system/app、vender/app、/data/app、/data/app-private这四个应用安装目录。因此如果能够将APK文件push进应用安装目录不就可以触发AppDirObserver中的包安装逻辑了了吗？所以这种思路理论上是行得通的，但有两个局限：
-
局限一：如下图所示，/system/app的访问权限为root，这就要求在push到/system/app目录时必须具有root权限。
而/data/app的访问权限为system。要获得system权限就要求使用这种方式的应用程序必须签名为platform并且sharedUserId制定为“android.uid.system”。
-
局限二：系统应用（/system/app)与普通应用(/data/app)的安装方式是不同的，对于系统应用，所有资源都包含在apk这个zip包中，而且其在/system/app不必以包名命名（理论上可以随便起名）。
而对于普通应用安装后，它的dex、lib、资源文件（安装包）分别存放在不同的目录，并且安装后以packagename-x.apk的形式保存在/data/app目录下。?
那这种安装方式是不是就没有用了呢?非也。
网上有些电子市场或管家类软件实现的”秒装“功能应该就是安装这个思路实现的，当然这里只是猜测，需要进一步研究。
2、调用Pm隐藏API
Android实现了一个应用安装器的APK负责包的安装工作，在上面的分析中我们知道，PackageInstaller的工作实际上只是安装界面、权限确认、进度显示等，真正的安装工作依然是调用Pms实现的。到这里我们就有了第二种思路，能不能绕过安装界面，直接调用Pms里面的相应方法呢？当然可以，PackageManager类中就提供了这样的方法：
@/frameworks/base/core/java/android/content/pm/PackageManager.java
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/**
* @hide
*
* Install a package. Since this may take a little while, the result will
* be posted back to the given observer. An installation will fail if the calling context
* lacks the {@link android.Manifest.permission#INSTALL_PACKAGES} permission, if the
* package named in the package file‘s manifest is already installed, or if there‘s no space
* available on the device.
*
* @param packageURI The location of the package file to install. This can be a ‘file:‘ or a
* ‘content:‘ URI.
* @param observer An observer callback to get notified when the package installation is
* complete. {@link IPackageInstallObserver#packageInstalled(String, int)} will be
* called when that happens. observer may be null to indicate that no callback is desired.
* @param flags - possible values: {@link #INSTALL_FORWARD_LOCK},
* {@link #INSTALL_REPLACE_EXISTING}, {@link #INSTALL_ALLOW_TEST}.
* @param installerPackageName Optional package name of the application that is performing the
* installation. This identifies which market the package came from.
*/
public abstract void installPackage(
Uri packageURI, IPackageInstallObserver observer, int flags,
String installerPackageName);
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可以看出，这个方法是hide的，因此在应用开发时如果要使用，必须通过反射。
这里的IPackageInstallObserver是installPackage方法的一个回调接口通知，其实现在IPackageInstallObserver.aidl中，如下：
@/frameworks/base/core/java/com/android/content/pm/IPackageInstallObserver.aidl
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package android.content.pm;
/**
* API for installation callbacks from the Package Manager.
* @hide
*/
oneway interface IPackageInstallObserver {
void packageInstalled(in String packageName, int returnCode);
}
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使用Android内置未公开API有两种方法：一种是通过反射的方式实现；另一种是在工程目录下建立与所引用系统类相同的类和方法，这里只要求类和方法名相同，不需要实现，只保证编译时不报错就可以了，根据Java的类加载机制，在运行时，会去加载系统类。下面是采用第二种方法时的两段示例代码：
实现接口回调的代码如下：
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class MyPakcageInstallObserver extends IPackageInstallObserver.Stub
{
Context
cxt;
String
appName;
String
filename;
String
pkname;
public MyPakcageInstallObserver(Context
c, String appName,
String
filename,String packagename) {
this.cxt
= c;
this.appName
= appName;
this.filename
= filename;
this.pkname
= packagename;
}
@Override
public void packageInstalled(String
packageName, int returnCode)
{
Log.i(TAG, "returnCode
= " +
returnCode);//
返回1代表安装成功
if (returnCode
== 1)
{
//TODO
}
Intent
it = new Intent();
it.setAction(CustomAction.INSTALL_ACTION);
it.putExtra("install_returnCode",
returnCode);
it.putExtra("install_packageName",
packageName);
it.putExtra("install_appName",
appName); cxt.sendBroadcast(it);
}
}
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调用PackageManager.java隐藏方法，代码如下：
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/**
*
静默安装
*
*/
public static void autoInstallApk(Context
context, String fileName,
String
packageName, String APPName) {
Log.d(TAG, "jing
mo an zhuang:" +
packageName + ",fileName:" +
fileName);
File
file = new File(fileName);
int installFlags
= 0;
if (!file.exists())
return;
installFlags
|= PackageManager.INSTALL_REPLACE_EXISTING;
if (hasSdcard())
{
installFlags
|= PackageManager.INSTALL_EXTERNAL;
}
PackageManager
pm = context.getPackageManager();
try {
IPackageInstallObserver
observer = new MyPakcageInstallObserver(
context,
APPName, appId, fileName,packageName,type_name);
Log.i(TAG, "########installFlags:" +
installFlags+"packagename:"+packageName);
pm.installPackage(Uri.fromFile(file),
observer, installFlags,
packageName);
} catch (Exception
e) {
}
}
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这种方法也有一定的限制：
首先，要在AndroidManifest.xml中声明”android.permission.INSTALL_PACKAGES”权限；
其次，应用需要system权限。
3、调用pm命令进行安装
在adb窗口通过pm install安装包本来就是没有安装界面的，这不正是我们想要的吗？通过pm的安装方式需要取得root或system权限。
pm的安装方式有两种，一种需要root权限，示例代码如下：
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new Thread()
{
public void run()
{
Process
process = null;
OutputStream
out = null;
InputStream
in = null;
try {
//
请求root
process
= Runtime.getRuntime().exec("su");
out
= process.getOutputStream();
//
调用安装
out.write(("pm
install -r " +
currentTempFilePath + "\n").getBytes());
in
= process.getInputStream();
int len
= 0;
byte[]
bs = new byte[256];
while (-1 !=
(len = in.read(bs))) {
String
state = new String(bs, 0,
len);
if (state.equals("Success\n"))
{
//安装成功后的操作
}
}
} catch (IOException
e) {
e.printStackTrace();
} catch (Exception
e) {
e.printStackTrace();
} finally {
try {
if (out
!= null)
{
out.flush();
out.close();
}
if (in
!= null)
{
in.close();
}
} catch (IOException
e) {
e.printStackTrace();
}
}
}
}.start();
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另一钟需要system权限，示例如下：
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new Thread() {
public void run() {
Process process = null;
InputStream in = null;
try {
// 请求root
process = Runtime.getRuntime().exec("pm install -r " + currentTempFilePath + "\n");
in = process.getInputStream();
int len = 0;
byte[] bs = new byte[256];
while (-1 != (len = in.read(bs))) {
String state = new String(bs, 0, len);
if (state.equals("Success\n")) {
//安装成功后的操作
}
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (in != null) {
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}.start();
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关于system权限的获取在介绍push方式的安装时已做介绍。上面的代码只给出了比较核心的部分，在实际实现中，对返回结果的处理同样重要。