Android App安装弹窗显示流程

一、APP的安装

1、常见安装方式
系统应用和预制应用安装――开机时完成，没有安装界面，在PKMS的构造函数中完成安装

网络下载或第三方应用安装――调用PackageManager.installPackages()，有安装界面。

ADB工具安装――没有安装界面，它通过启动pm脚本的形式，然后调用com.android.commands.pm.Pm类，之后调用到PMS.installStage()完成安装。
2、APK的签名校验理解

V1签名apk-signature-v1-location.png只是校验了apk资源,并没有约束zip,签名信息存储在zip/META-INF中。

v2签名是一个对全文件进行签名的方案,能提供更快的应用安装时间、对未授权APK文件的更改提供更多保护.

3、APK安装过程

开机后扫描应用安装目录和系统App目录，解析其中的apk文件将相关信息加载到PKMS中的数据结构中，同时对于没有对应数据目录的App生成对应的数据目录
注册包名App等信息、以及相关的四大组件到PMS中
将解析到的数据同步到/data/system/packages.xml中

4、App安装涉及的目录理解
系统App安装目录

1、 /system/app: Android系统App路径
2、/system/priv-app: 同上，但比/system/app权限优先级更高，可以拿到ApplicationInfo.PRIVATE_FLAG_PRIVILEGED特殊权限
3、/vendor/app: odm或者oem厂商预制系统App目录
4、/vendor/priva-app: 同上

普通应用App安装目录

/data/app：用户App程序安装的目录。安装时Apk会被拷贝至此目录

用户数据目录

/data/data：存放应用程序的数据,无论是系统App还是普通App,App产生的用户数据都存放在/data/data/包名/目录下。

App注册表目录

/data/system
1、packages.xml:
记录apk的permissions,flags,ts,version,uesrid等信息，这些信息主要通apk的AndroidManifest.xml解析获取，当系统进行程序安装、卸载和更新等操作时，均会更新该文件。
2、packages-backup.xml : 备份文件
3、packages-stopped.xml : 记录被用户强行停止的应用的Package信息
4、packages-stopped-backup.xml : pakcages-stoped.xml文件的备份
5、packages.list : 记录非系统自带的APK的数据信息，这些APK有变化时会更新该文件

5、package.xml文件解析

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<packages>
    <version sdkVersion="xxx" databaseVersion="xxx" fingerprint="xxx" />
    <version volumeUuid="xxx" sdkVersion="xxx" databaseVersion="xxx" fingerprint="xxx" />

    <permissions>
        <item name="android.permission.REAL_GET_TASKS" package="android" protection="18" />
        ...
    </permissions>   
  
    <package name="com.android.providers.telephony" codePath="/system/priv-app/TelephonyProvider" nativeLibraryPath="/system/priv-app/TelephonyProvider/lib" publicFlags="1007402501" privateFlags="8" ft="11e8dc5d800" it="11e8dc5d800" ut="11e8dc5d800" version="25" versionName="7.1.2" applicationName="电话和短信存储" sharedUserId="1001" isOrphaned="true">
        <sigs count="1">
            <cert index="1" key="xxx" />
        </sigs>
        <perms>
            <item name="android.permission.WRITE_SETTINGS" granted="true" flags="0" />
            ...
        </perms>
        <proper-signing-keyset identifier="1" />
    </package>  
    ...       
    
    <updated-package name="xxx.xxx.xxx" codePath="/system/app/xxx" ft="11e8dc5d800" it="11e8dc5d800" ut="11e8dc5d800" version="11" nativeLibraryPath="/system/app/xxx/lib" primaryCpuAbi="armeabi-v7a" sharedUserId="1000" />


    <shared-user name="android.media" userId="10005">
        <sigs count="1">
            <cert index="2" />
        </sigs>
        <perms>
            <item name="android.permission.ACCESS_CACHE_FILESYSTEM" granted="true" flags="0" />
            ...
        </perms>
    </shared-user>
    ...
</packages>   

package.xml对应的类图关系
BasePermission

BasePermission对应packages.xml中permissions标签的子标签item，对于上述所定义的每一项权限都会生成一个BasePermission。
protection ：等级分为四个
1、普通权限（normal）
2、运行时权限（dangerous）
3、签名权限（signature）
4、特殊权限（privileged）

    <permissions>
        <item name="android.permission.REAL_GET_TASKS" package="android" protection="18" />
        ...
    <permissions/>  

PermissionsState

PermissionState对应的是标签中的子标签标签中的内容

<package name="com.android.providers.telephony" codePath="/system/priv-app/TelephonyProvider" nativeLibraryPath="/system/priv-app/TelephonyProvider/lib" publicFlags="1007402501" privateFlags="8" ft="11e8dc5d800" it="11e8dc5d800" ut="11e8dc5d800" version="25" versionName="7.1.2" applicationName="电话和短信存储" sharedUserId="1001" isOrphaned="true">
        <perms>
            <item name="android.permission.WRITE_SETTINGS" granted="true" flags="0" />
            ...
        </perms>
</package>

PackageSignatures

PackageSignatures对应的是<package>标签中的子标签<sigs>标签中的内容

<package name="com.android.providers.telephony" codePath="/system/priv-app/TelephonyProvider" nativeLibraryPath="/system/priv-app/TelephonyProvider/lib" publicFlags="1007402501" privateFlags="8" ft="11e8dc5d800" it="11e8dc5d800" ut="11e8dc5d800" version="25" versionName="7.1.2" applicationName="电话和短信存储" sharedUserId="1001" isOrphaned="true">
        <sigs count="1">
            <cert index="1" key="xxx" />
        </sigs>
</package>

PackageSetting

PackageSetting这个数据结构类是packages.xml里面记录安装包信息标签相对应的类，可以看到PackageSetting继承了PackageSettingBase类，PackageSettingBase类继承自SettingBase类。应用的基本信息保存在PackageSettingBase类的成员变量中，签名则保存在PackageSignatures中，权限状态保存在父类的SettingBase的PermissionsState中。

 <package name="com.android.providers.telephony" codePath="/system/priv-app/TelephonyProvider" nativeLibraryPath="/system/priv-app/TelephonyProvider/lib" publicFlags="1007402501" privateFlags="8" ft="11e8dc5d800" it="11e8dc5d800" ut="11e8dc5d800" version="25" versionName="7.1.2" applicationName="电话和短信存储" sharedUserId="1001" isOrphaned="true">
        <sigs count="1">
            <cert index="1" key="xxx" />
        </sigs>
        <perms>
            <item name="android.permission.WRITE_SETTINGS" granted="true" flags="0" />
            ...
        </perms>
        <proper-signing-keyset identifier="1" />
</package>  

SharedUserSetting

SharedUserSetting这个数据结构类是packages.xml里面记录安装包信息标签相对应的类，它和PackageSetting有一个共同的父类即SettingBase，即都是通过父类的PermissionsState来保存权限信息。SharedUserSetting被设计的用途主要用来描述具有相同的sharedUserId的应用信息，它的成员变量packages保存了所有具有相同sharedUserId的应用信息引用，而成员变量userId则是记录多个APK共享的UID。共享用户的应用的签名是相同的，签名保存在成员变量signatures中(这里有一点需要注意，由于签名相同，Android运行时很容易检索到某个应用拥有相同的sharedUserId的其他应用)。

 <shared-user name="android.media" userId="10005">
        <sigs count="1">
            <cert index="2" />
        </sigs>
        <perms>
            <item name="android.permission.ACCESS_CACHE_FILESYSTEM" granted="true" flags="0" />
            ...
        </perms>
</shared-user>

Settings : package.xml 终极大管家类

二、APP安装整体流程

代码仓库：http://androidxref.com/9.0.0_r3/xref/packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallStart.java

1、安装APP代码入口

    <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>

2、根据Uri的Scheme协议不同，跳转到不同的界面
content协议跳转到InstallStaging，package协议跳转到PackageInstallerActivity

 protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ......
        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);

        //1、content的Uri协议 ： InstallStaging 
        //2、package的Url协议：PackageInstallerActivity 
        if (PackageInstaller.ACTION_CONFIRM_PERMISSIONS.equals(intent.getAction())) {
    
    
            nextActivity.setClass(this, PackageInstallerActivity.class);
        } else {
    
    
            Uri packageUri = intent.getData();

            if (packageUri != null && (packageUri.getScheme().equals(ContentResolver.SCHEME_FILE)
                    || packageUri.getScheme().equals(ContentResolver.SCHEME_CONTENT))) {
    
    
                // Copy file to prevent it from being changed underneath this process
                   //1、content的Uri协议 ： InstallStaging 
                nextActivity.setClass(this, InstallStaging.class);
            } else if (packageUri != null && packageUri.getScheme().equals(
                    PackageInstallerActivity.SCHEME_PACKAGE)) {
    
    
                //package的Url协议：PackageInstallerActivity 
                nextActivity.setClass(this, PackageInstallerActivity.class);
            } else {
    
    
                Intent result = new Intent();
                result.putExtra(Intent.EXTRA_INSTALL_RESULT,
                        PackageManager.INSTALL_FAILED_INVALID_URI);
                setResult(RESULT_FIRST_USER, result);

                nextActivity = null;
            }
        }
        
        if (nextActivity != null) {
    
    
            startActivity(nextActivity);
        }
        finish();
    }

3、InstallStaging类的介绍

主要内容：将content协议的Uri转换为package协议的Uri,然后通过IO形式写入到mStagedFile文件中
作用：主要起了转换的作用，将content协议的Uri转换为package协议，然后跳转到PackageInstallerActivity

@Override
  protected void onResume() {
    
    
      super.onResume();
      if (mStagingTask == null) {
    
    
          if (mStagedFile == null) {
    
    
              try {
    
    
                  mStagedFile = TemporaryFileManager.getStagedFile(this);
              } catch (IOException e) {
    
    
                  showError();
                  return;
              }
          }
          mStagingTask = new StagingAsyncTask();
          mStagingTask.execute(getIntent().getData());
      }
  }

 private final class StagingAsyncTask extends AsyncTask<Uri, Void, Boolean> {
    
    
        @Override
        protected Boolean doInBackground(Uri... params) {
    
    
            if (params == null || params.length <= 0) {
    
    
                return false;
            }
            Uri packageUri = params[0];
            try (InputStream in = getContentResolver().openInputStream(packageUri)) {
    
    
                if (in == null) {
    
    
                    return false;
                }
                try (OutputStream out = new FileOutputStream(mStagedFile)) {
    
    
                    byte[] buffer = new byte[4096];
                    int bytesRead;
                    while ((bytesRead = in.read(buffer)) >= 0) {
    
    
                        if (isCancelled()) {
    
    
                            return false;
                        }
                        out.write(buffer, 0, bytesRead);
                    }
                }
            } catch (IOException | SecurityException e) {
    
    
                Log.w(LOG_TAG, "Error staging apk from content URI", e);
                return false;
            }
            return true;
        }
        @Override
        protected void onPostExecute(Boolean success) {
    
    
           if (session != null) {
    
    
         Intent broadcastIntent = new Intent(BROADCAST_ACTION);
         broadcastIntent.setPackage(
                 getPackageManager().getPermissionControllerPackageName());
         broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId);
         PendingIntent pendingIntent = PendingIntent.getBroadcast(
                 InstallInstalling.this,
                 mInstallId,
                 broadcastIntent,
                 PendingIntent.FLAG_UPDATE_CURRENT);
        //APP安装的启动入口
         session.commit(pendingIntent.getIntentSender());
         mCancelButton.setEnabled(false);
         setFinishOnTouchOutside(false);
     } else {
    
    
         getPackageManager().getPackageInstaller().abandonSession(mSessionId);
         if (!isCancelled()) {
    
    
             launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
         }
     }
}

4、PackageInstallerActivity类的介绍
它就是在安装应用显示弹窗的Activity

@Override
protected void onCreate(Bundle icicle) {
    
    
    super.onCreate(icicle);
    if (icicle != null) {
    
    
        mAllowUnknownSources = icicle.getBoolean(ALLOW_UNKNOWN_SOURCES_KEY);
    }
    mPm = getPackageManager();
    mIpm = AppGlobals.getPackageManager();
    mAppOpsManager = (AppOpsManager) getSystemService(Context.APP_OPS_SERVICE);
    mInstaller = mPm.getPackageInstaller();
    mUserManager = (UserManager) getSystemService(Context.USER_SERVICE);
    ...
    //根据Uri的Scheme进行预处理
    boolean wasSetUp = processPackageUri(packageUri);
    if (!wasSetUp) {
    
    
        return;
    }
    bindUi(R.layout.install_confirm, false);
    //判断是否是未知来源的应用，如果开启允许安装未知来源选项则直接初始化安装
    checkIfAllowedAndInitiateInstall();
}

分别对content和package两种不同协议处理

private boolean processPackageUri(final Uri packageUri) {
    
    
     mPackageURI = packageUri;
     final String scheme = packageUri.getScheme();//1
     switch (scheme) {
    
    
         case SCHEME_PACKAGE: {
    
    
             try {
    
    
              ...
         } break;
         case SCHEME_FILE: {
    
    
             File sourceFile = new File(packageUri.getPath());
             //得到sourceFile的包信息
             PackageParser.Package parsed = PackageUtil.getPackageInfo(this, sourceFile);
             if (parsed == null) {
    
    
                 Log.w(TAG, "Parse error when parsing manifest. Discontinuing installation");
                 showDialogInner(DLG_PACKAGE_ERROR);
                 setPmResult(PackageManager.INSTALL_FAILED_INVALID_APK);
                 return false;
             }
             //对parsed进行进一步处理得到包信息PackageInfo
             mPkgInfo = PackageParser.generatePackageInfo(parsed, null,
                     PackageManager.GET_PERMISSIONS, 0, 0, null,
                     new PackageUserState());//3
             mAppSnippet = PackageUtil.getAppSnippet(this, mPkgInfo.applicationInfo, sourceFile);
         } break;
         default: {
    
    
             Log.w(TAG, "Unsupported scheme " + scheme);
             setPmResult(PackageManager.INSTALL_FAILED_INVALID_URI);
             finish();
             return false;
         }
     }
     return true;
 }

弹窗上显示是否是非法安装的处理

private void checkIfAllowedAndInitiateInstall() {
    
    
       //判断如果允许安装未知来源或者根据Intent判断得出该APK不是未知来源
       if (mAllowUnknownSources || !isInstallRequestFromUnknownSource(getIntent())) {
    
    
           //初始化安装
           initiateInstall();
           return;
       }
       // 如果管理员限制来自未知源的安装, 就弹出提示Dialog或者跳转到设置界面
       if (isUnknownSourcesDisallowed()) {
    
    
           if ((mUserManager.getUserRestrictionSource(UserManager.DISALLOW_INSTALL_UNKNOWN_SOURCES,
                   Process.myUserHandle()) & UserManager.RESTRICTION_SOURCE_SYSTEM) != 0) {
    
        
               showDialogInner(DLG_UNKNOWN_SOURCES_RESTRICTED_FOR_USER);
               return;
           } else {
    
    
               startActivity(new Intent(Settings.ACTION_SHOW_ADMIN_SUPPORT_DETAILS));
               finish();
           }
       } else {
    
    
           handleUnknownSources();
       }
   }

InstallStaging.java session.commit() 去执行系统framework层

 protected void onPostExecute(Boolean success) {
    
    
           if (session != null) {
    
    
         Intent broadcastIntent = new Intent(BROADCAST_ACTION);
         broadcastIntent.setPackage(
                 getPackageManager().getPermissionControllerPackageName());
         broadcastIntent.putExtra(EventResultPersister.EXTRA_ID, mInstallId);
         PendingIntent pendingIntent = PendingIntent.getBroadcast(
                 InstallInstalling.this,
                 mInstallId,
                 broadcastIntent,
                 PendingIntent.FLAG_UPDATE_CURRENT);
        //APP安装的启动入口
         session.commit(pendingIntent.getIntentSender());
         mCancelButton.setEnabled(false);
         setFinishOnTouchOutside(false);
     } else {
    
    
         getPackageManager().getPackageInstaller().abandonSession(mSessionId);
         if (!isCancelled()) {
    
    
             launchFailure(PackageManager.INSTALL_FAILED_INVALID_APK, null);
         }
     }

PackageInstaller.java 类

public void commit(@NonNull IntentSender statusReceiver) {
    
    
           try {
    
    
               mSession.commit(statusReceiver);
           } catch (RemoteException e) {
    
    
               throw e.rethrowFromSystemServer();
           }
       }

PackageInstallerSession.java类
PackageInstallObserverAdapter继承PackageInstallObserver : 监听安装APP的过程
mSessionId是安装包的会话id，mInstallId是等待的安装事件id

@Override
   public void commit(IntentSender statusReceiver) {
    
    
       Preconditions.checkNotNull(statusReceiver);
       ...
       mActiveCount.incrementAndGet();
       final PackageInstallObserverAdapter adapter = new PackageInstallObserverAdapter(mContext,
               statusReceiver, sessionId, mIsInstallerDeviceOwner, userId);
      //Handler发送一个类型为MSG_COMMIT的消息，通知PMS安装应用
       mHandler.obtainMessage(MSG_COMMIT, adapter.getBinder()).sendToTarget();
   }

private final Handler.Callback mHandlerCallback = new Handler.Callback() {
    
    
      @Override
      public boolean handleMessage(Message msg) {
    
    
          final PackageInfo pkgInfo = mPm.getPackageInfo(
                  params.appPackageName, PackageManager.GET_SIGNATURES
                          | PackageManager.MATCH_STATIC_SHARED_LIBRARIES /*flags*/, userId);
          final ApplicationInfo appInfo = mPm.getApplicationInfo(
                  params.appPackageName, 0, userId);
          synchronized (mLock) {
    
    
              if (msg.obj != null) {
    
    
                  mRemoteObserver = (IPackageInstallObserver2) msg.obj;
              }
              try {
    
    
                  //PMS开始安装应用
                  commitLocked(pkgInfo, appInfo);
              } catch (PackageManagerException e) {
    
    
                  final String completeMsg = ExceptionUtils.getCompleteMessage(e);
                  Slog.e(TAG, "Commit of session " + sessionId + " failed: " + completeMsg);
                  destroyInternal();
                   //安装时候出现异常问题
                  dispatchSessionFinished(e.error, completeMsg, null);
              }
              return true;
          }
      }
  };

private void commitLocked(PackageInfo pkgInfo, ApplicationInfo appInfo)
          throws PackageManagerException {
    
    
     ...
    //通知 PMS开始安装应用
      mPm.installStage(mPackageName, stageDir, stageCid, localObserver, params,
              installerPackageName, installerUid, user, mCertificates);
  }

总结：

根据Uri的Scheme协议不同，跳转到不同的界面，content协议跳转到InstallStaging，package跳转到PackageInstallerActivity。
InstallStaging将content协议的Uri转换为File协议，然后跳转到PackageInstallerActivity。
PackageInstallerActivity会分别对package协议和file协议的Uri进行处理，如果是file协议会解析APK文件得到包信息PackageInfo。
PackageInstallerActivity中会对未知来源进行处理，如果允许安装未知来源或者根据Intent判断得出该APK不是未知来源，就会初始化安装确认界面，如果管理员限制来自未知源的安装, 就弹出提示Dialog或者跳转到设置界面。