APK的安装有很多方式，应用商城下载、文件浏览器安装、adb命令安装，我们以文件浏览器为例。
将一个APK文件放到SD卡目录下，文件浏览器显示apk文件。
当我们点击APK文件时，文件浏览器根据文件的后缀(.apk)解析，执行startActivity，调起packageinstaller.PackageInstallerActivity。
ActivityManager: START u0 {act=android.intent.action.VIEW dat=file:///storage/emulated/0/com.dewmobile.kuaiya.apk typ=application/vnd.android.package-archive flg=0x88000 cmp=com.android.packageinstaller/.PackageInstallerActivity} from uid 10032 on display 0
PackageInstallerActivity
PackageInstallerActivity这个类的主要作用是显示安装弹窗，对APK进行解析，判断是否允许未知来源安装，判断应用权限，等待用户安装。
packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java
public void onClick(View v) {
if (v == mOk) {
if (mOkCanInstall || mScrollView == null) {
if (mSessionId != -1) {
mInstaller.setPermissionsResult(mSessionId, true);
clearCachedApkIfNeededAndFinish();
} else {
startInstall(); //开始安装
}
} else {
mScrollView.pageScroll(View.FOCUS_DOWN);
}
} else if (v == mCancel) {
// Cancel and finish
setResult(RESULT_CANCELED);
if (mSessionId != -1) {
mInstaller.setPermissionsResult(mSessionId, false);
}
clearCachedApkIfNeededAndFinish();
}
}
然后用户点击安装按钮，就会调用startInstall()函数
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);
newIntent.setClass(this, InstallAppProgress.class);//
String installerPackageName = getIntent().getStringExtra(
Intent.EXTRA_INSTALLER_PACKAGE_NAME);
......
if(localLOGV) Log.i(TAG, "downloaded app uri="+mPackageURI);
startActivity(newIntent);
finish();
}
startInstall函数用于跳转到InstallAppProgress这个Activity，关闭PackageInstallerActivity。
InstallAppProgress
InstallAppProgress主要用于展示安装界面、向PMS发送包信息， 处理回调。
packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallAppProgress.java
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
Intent intent = getIntent();
mAppInfo = intent.getParcelableExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO);
mPackageURI = intent.getData();
final String scheme = mPackageURI.getScheme();
if (scheme != null && !"file".equals(scheme) && !"package".equals(scheme)) {
throw new IllegalArgumentException("unexpected scheme " + scheme);
}
// 开启安装线程
mInstallThread = new HandlerThread("InstallThread");
mInstallThread.start();
mInstallHandler = new Handler(mInstallThread.getLooper());
//注册安装监听
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BROADCAST_ACTION);
registerReceiver(
mBroadcastReceiver, intentFilter, BROADCAST_SENDER_PERMISSION, null /*scheduler*/);
initView();
}
InstallAppProgress中启动了一个HandlerThread，开启安装线程，注册了一个广播，这个广播用来监听系统返回的安装结果。
主要代码在在initView()函数中
final PackageInstaller.SessionParams params = new PackageInstaller.SessionParams(
PackageInstaller.SessionParams.MODE_FULL_INSTALL);
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());
try {
//解析安装包，设置安装位置，从AndroidManifest中获取
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(TAG, "Cannot parse package " + file + ". Assuming defaults.");
Log.e(TAG, "Cannot calculate installed size " + file + ". Try only apk size.");
params.setSize(file.length());
} catch (IOException e) {
Log.e(TAG, "Cannot calculate installed size " + file + ". Try only apk size.");
params.setSize(file.length());
}
mInstallHandler.post(new Runnable() {
@Override
public void run() {
//执行安装
doPackageStage(pm, params);
}
});
private void doPackageStage(PackageManager pm, PackageInstaller.SessionParams params) {
//初始化安装器
final PackageInstaller packageInstaller = pm.getPackageInstaller();
PackageInstaller.Session session = null;
try {
final String packageLocation = mPackageURI.getPath();
final File file = new File(packageLocation);
//获取sessionId
final int sessionId = packageInstaller.createSession(params);
final byte[] buffer = new byte[65536];
//获取session
session = packageInstaller.openSession(sessionId);
final InputStream in = new FileInputStream(file);
final long sizeBytes = file.length();
// 根据这个session回话, 获取一个OutPutstream, 然后将文件写入到这个OutPutStream中
final OutputStream out = session.openWrite("PackageInstaller", 0, sizeBytes);
try {
int c;
while ((c = in.read(buffer)) != -1) {
out.write(buffer, 0, c);
if (sizeBytes > 0) {
final float fraction = ((float) c / (float) sizeBytes);
//安装中
session.addProgress(fraction);
}
}
session.fsync(out);
} finally {
IoUtils.closeQuietly(in);
IoUtils.closeQuietly(out);
}
// Create a PendingIntent and use it to generate the IntentSender
Intent broadcastIntent = new Intent(BROADCAST_ACTION);
PendingIntent pendingIntent = PendingIntent.getBroadcast(
InstallAppProgress.this /*context*/,
sessionId,
broadcastIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
//最后调用session的commit方法进行提交
session.commit(pendingIntent.getIntentSender());
} catch (IOException e) {
onPackageInstalled(PackageInstaller.STATUS_FAILURE);
} finally {
IoUtils.closeQuietly(session);
}
}
最终广播接受安装结果
private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
final int statusCode = intent.getIntExtra(
PackageInstaller.EXTRA_STATUS, PackageInstaller.STATUS_FAILURE);
if (statusCode == PackageInstaller.STATUS_PENDING_USER_ACTION) {
context.startActivity((Intent)intent.getParcelableExtra(Intent.EXTRA_INTENT));
} else {
onPackageInstalled(statusCode);
}
}
};
应用安装的前期工作，用户可以看到的部分基本就这些，接下来的工作就都由Java框架层处理。
Java框架层
上面最终调用PackageInstallerSession的commit方法，将安装APK的信息发给框架层。
frameworks/base/services/core/java/com/android/server/pm/PackageInstallerSession.java
@Override
public void commit(IntentSender statusReceiver) {
......
mActiveCount.incrementAndGet();
final PackageInstallObserverAdapter adapter = new PackageInstallObserverAdapter(mContext,
statusReceiver, sessionId, mIsInstallerDeviceOwner, userId);
mHandler.obtainMessage(MSG_COMMIT, adapter.getBinder()).sendToTarget();
}
commit函数中向Handler发送一个类型为MSG_COMMIT的消息，adapter.getBinder()会得到IPackageInstallObserver2观察者，处理消息逻辑如下：
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) {
// Cache package manager data without the lock held
final PackageInfo pkgInfo = mPm.getPackageInfo(
params.appPackageName, PackageManager.GET_SIGNATURES /*flags*/, userId);
final ApplicationInfo appInfo = mPm.getApplicationInfo(
params.appPackageName, 0, userId);
synchronized (mLock) {
if (msg.obj != null) {
mRemoteObserver = (IPackageInstallObserver2) msg.obj;
}
try {
commitLocked(pkgInfo, appInfo);
} catch (PackageManagerException e) {
final String completeMsg = ExceptionUtils.getCompleteMessage(e);
Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg);
destroyInternal();
dispatchSessionFinished(e.error, completeMsg, null);
}
return true;
}
}
};
private void commitLocked(PackageInfo pkgInfo, ApplicationInfo appInfo)
throws PackageManagerException {
...
mPm.installStage(mPackageName, stageDir, stageCid, localObserver, params,
installerPackageName, installerUid, user, mCertificates);
}
在commitLocked方法中，调用PMS的installStage方法，这样逻辑就进入PMS中了。
总结
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。
