【Android】APK应用安装过程源码解析
Android系统在启动的过程中，会启动一个应用程序管理服务PackageManagerService，这个服务负责扫描系统中特定的目录，找到里面的应用程序文件，即以Apk为后缀的文件，然后对这些文件进解析，得到应用程序的相关信息，完成应用程序的安装过程，本文将详细分析这个过程。
一、启动安装
1、InstallStart
在开发过程中有时候需要进行APP更新，或者下载其他APP到本地让后使用以下代码进行安装，我这里单单讲解在执行startActivity之后的运行过程。
Intent intent = new Intent(Intent.ACTION_VIEW);
//设置intent的数据类型是应用程序application
intent.setDataAndType(Uri.parse("file://" + apkfile.toString()), "application/vnd.android.package-archive");
//为这个新apk开启一个新的activity栈
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
//开始安装
startActivity(intent);
在执行完这几行代码后会启动系统的一个APP进行APK的安装，我们可以通过源码查看在系统中有一个packageinstaller的系统应用。然后首先查看看清单文件
<activity android:name=".InstallStart"
android:exported="true"
android:excludeFromRecents="true">
<intent-filter android:priority="1">
<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:scheme="content" />
<data android:mimeType="application/vnd.android.package-archive" />
intent-filter>
<intent-filter android:priority="1">
<action android:name="android.intent.action.INSTALL_PACKAGE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="file" />
<data android:scheme="package" />
<data android:scheme="content" />
intent-filter>
<intent-filter android:priority="1">
<action android:name="android.content.pm.action.CONFIRM_PERMISSIONS" />
<category android:name="android.intent.category.DEFAULT" />
intent-filter>
activity>
从中可以发现首先启动的是名为InstallStart的Activity，由于整个源码有点多，因此这里只是贴出部分重要方法。在这里只需要看onCreate的方法
import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInstaller;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
public class InstallStart extends Activity {
private static final String LOG_TAG = InstallStart.class.getSimpleName();
private static final String SCHEME_CONTENT = "content";
private static final String DOWNLOADS_AUTHORITY = "downloads";
private IActivityManager mIActivityManager;
private IPackageManager mIPackageManager;
private boolean mAbortInstall = false;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mIPackageManager = AppGlobals.getPackageManager();
Intent intent = getIntent();
String callingPackage = getCallingPackage();
// If the activity was started via a PackageInstaller session, we retrieve the calling
// package from that session
int sessionId = intent.getIntExtra(PackageInstaller.EXTRA_SESSION_ID, -1);
if (callingPackage == null && sessionId != -1) {
//我们第三发安装sessionId为-1
PackageInstaller packageInstaller = getPackageManager().getPackageInstaller();
PackageInstaller.SessionInfo sessionInfo = packageInstaller.getSessionInfo(sessionId);
callingPackage = (sessionInfo != null) ? sessionInfo.getInstallerPackageName() : null;
}
final ApplicationInfo sourceInfo = getSourceInfo(callingPackage);
final int originatingUid = getOriginatingUid(sourceInfo);
boolean isTrustedSource = false;
if (sourceInfo != null
&& (sourceInfo.privateFlags & ApplicationInfo.PRIVATE_FLAG_PRIVILEGED) != 0) {
isTrustedSource = intent.getBooleanExtra(Intent.EXTRA_NOT_UNKNOWN_SOURCE, false);
}
if (!isTrustedSource && originatingUid != PackageInstaller.SessionParams.UID_UNKNOWN) {
final int targetSdkVersion = getMaxTargetSdkVersionForUid(originatingUid);
if (targetSdkVersion < 0) {
Log.w(LOG_TAG, "Cannot get target sdk version for uid " + originatingUid);
// Invalid originating uid supplied. Abort install.
mAbortInstall = true;
} else if (targetSdkVersion >= Build.VERSION_CODES.O && !declaresAppOpPermission(
originatingUid, Manifest.permission.REQUEST_INSTALL_PACKAGES)) {
//在现版本第三方安装APK需要申明REQUEST_INSTALL_PACKAGES权限，declaresAppOpPermission检测
//是否申请改权限
Log.e(LOG_TAG, "Requesting uid " + originatingUid + " needs to declare permission "
+ Manifest.permission.REQUEST_INSTALL_PACKAGES);
mAbortInstall = true;
}
}
if (mAbortInstall) {
//如果经过上述一系列操作没问题，当然是false
setResult(RESULT_CANCELED);
finish();
return;
}
Intent nextActivity = new Intent(intent);
nextActivity.setFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
// The the installation source as the nextActivity thinks this activity is the source, hence
// set the originating UID and sourceInfo explicitly
nextActivity.putExtra(PackageInstallerActivity.EXTRA_CALLING_PACKAGE, callingPackage);
nextActivity.putExtra(PackageInstallerActivity.EXTRA_ORIGINAL_SOURCE_INFO, sourceInfo);
nextActivity.putExtra(Intent.EXTRA_ORIGINATING_UID, originatingUid);
if (PackageInstaller.ACTION_CONFIRM_PERMISSIONS.equals(intent.getAction())) {
//在这里我们第三方app是不会跳转到这里的
nextActivity.setClass(this, PackageInstallerActivity.class);
} else {
Uri packageUri = intent.getData();
if (packageUri == null) {
// if there's nothing to do, quietly slip into the ether
Intent result = new Intent();
result.putExtra(Intent.EXTRA_INSTALL_RESULT,
PackageManager.INSTALL_FAILED_INVALID_URI);
setResult(RESULT_FIRST_USER, result);
nextActivity = null;
} else {
if (packageUri.getScheme().equals(SCHEME_CONTENT)) {
nextActivity.setClass(this, InstallStaging.class);
} else {
nextActivity.setClass(this, PackageInstallerActivity.class);
}
}
}
if (nextActivity != null) {
//跳转到下一个Activity
startActivity(nextActivity);
}
finish();
}
......
}
经过一系列的解析操作之后会跳转到新的界面
2、PackageInstallerActivity
public class PackageInstallerActivity extends OverlayTouchActivity implements OnClickListener {
private static final String TAG = "PackageInstaller";
.....
@Override
protected void onCreate(Bundle icicle) {
super.onCreate(icicle);
if (icicle != null) {
mAllowUnknownSources = icicle.getBoolean(ALLOW_UNKNOWN_SOURCES_KEY);
}
mPm = getPackageManager(); //获取PackageManager
mIpm = AppGlobals.getPackageManager();
mAppOpsManager = (AppOpsManager) getSystemService(Context.APP_OPS_SERVICE);
mInstaller = mPm.getPackageInstaller();//获取PackageInstaller
mUserManager = (UserManager) getSystemService(Context.USER_SERVICE);
final Intent intent = getIntent();
mCallingPackage = intent.getStringExtra(EXTRA_CALLING_PACKAGE);
mSourceInfo = intent.getParcelableExtra(EXTRA_ORIGINAL_SOURCE_INFO);
mOriginatingUid = intent.getIntExtra(Intent.EXTRA_ORIGINATING_UID,
PackageInstaller.SessionParams.UID_UNKNOWN);
mOriginatingPackage = (mOriginatingUid != PackageInstaller.SessionParams.UID_UNKNOWN)
? getPackageNameForUid(mOriginatingUid) : null;
final Uri packageUri;
if (PackageInstaller.ACTION_CONFIRM_PERMISSIONS.equals(intent.getAction())) {
//非Android的GooglePaly上的app可以直接忽略了
final int sessionId = intent.getIntExtra(PackageInstaller.EXTRA_SESSION_ID, -1);
final PackageInstaller.SessionInfo info = mInstaller.getSessionInfo(sessionId); //在PackageInstaller中创建一个Session
if (info == null || !info.sealed || info.resolvedBaseCodePath == null) {
Log.w(TAG, "Session " + mSessionId + " in funky state; ignoring");
finish();
return;
}
mSessionId = sessionId;//
packageUri = Uri.fromFile(new File(info.resolvedBaseCodePath));
mOriginatingURI = null;
mReferrerURI = null;
} else {
mSessionId =