WebAPK: Move MainActivity#onCreate() to runtime library

chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/WebApkServiceFactory.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.webapk.shell_apk;
 
 import android.app.Service;
 import android.content.Context;
 import android.content.Intent;
-import android.content.SharedPreferences;
-import android.content.pm.PackageInfo;
-import android.content.pm.PackageManager;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.util.Log;
 
 import org.chromium.webapk.lib.common.WebApkUtils;
 
-import java.io.File;
 import java.lang.reflect.Constructor;
-import java.util.Scanner;
 
 /**
  * Shell class for services provided by WebAPK to Chrome. Extracts code with implementation of
  * services from .dex file in Chrome APK.
  */
 public class WebApkServiceFactory extends Service {
     private static final String TAG = "cr_WebApkServiceFactory";
 
     /**
      * Name of the class with IBinder API implementation.
      */
     private static final String WEBAPK_SERVICE_IMPL_CLASS_NAME =
             "org.chromium.webapk.lib.runtime_library.WebApkServiceImpl";
 
     /**
-     * Name of the shared preferences file.
-     */
-    private static final String PREF_PACKAGE = "org.chromium.webapk.shell_apk";
-
-    /**
-     * Name of the shared preference for Chrome's version code.
-     */
-    private static final String REMOTE_VERSION_CODE_PREF =
-            "org.chromium.webapk.shell_apk.version_code";
-
-    /**
-     * Name of the shared preference for the version number of the dynamically loaded dex.
-     */
-    private static final String RUNTIME_DEX_VERSION_PREF =
-            "org.chromium.webapk.shell_apk.dex_version";
-
-    /**
      * Key for passing id of icon to represent WebAPK notifications in status bar.
      */
     private static final String KEY_SMALL_ICON_ID = "small_icon_id";
 
     /**
      * Key for passing package name of only process allowed to call the service's methods.
      */
     private static final String KEY_HOST_BROWSER_PACKAGE = "host_browser_package";
 
-    /*
-     * ClassLoader for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}. Static so that all
-     * {@link WebApkServiceFactory} service instatiations use the same ClassLoader during the app's
-     * lifetime.
-     */
-    private static ClassLoader sClassLoader;
-
     @Override
     public IBinder onBind(Intent intent) {
-        ClassLoader webApkClassLoader = getClassLoaderInstance(this);
+        ClassLoader webApkClassLoader =
+                HostBrowserClassLoader.getClassLoaderInstance(this, WEBAPK_SERVICE_IMPL_CLASS_NAME);

[Xi Han, 2016/06/27 18:27:08]

Is it good to move the call to get ClassLoader in onCreate()?

[pkotwicz, 2016/06/27 20:44:28]

It is not important that interacting with the WebAPK service is fast, so I do
not think that moving the HostBrowserClassLoader#getClassLoaderInstance()
invocation to onCreate() is helpful. I am also unsure whether moving the
invocation to onCreate() will speed things up.

[Xi Han, 2016/06/28 13:53:39]

I don't have strong opinion on this, it seems ok since getClassLoaderInstance
returns the static instance directly if it is not null.

         if (webApkClassLoader == null) {
             Log.w(TAG, "Unable to create ClassLoader.");
             return null;
         }
 
         try {
             Class<?> webApkServiceImplClass =
                     webApkClassLoader.loadClass(WEBAPK_SERVICE_IMPL_CLASS_NAME);
             Constructor<?> webApkServiceImplConstructor =
                     webApkServiceImplClass.getConstructor(Context.class, Bundle.class);
             String hostPackageName = WebApkUtils.getHostBrowserPackageName(this);
             Bundle bundle = new Bundle();
             bundle.putInt(KEY_SMALL_ICON_ID, R.drawable.app_icon);
             bundle.putString(KEY_HOST_BROWSER_PACKAGE, hostPackageName);
             return (IBinder) webApkServiceImplConstructor.newInstance(new Object[] {this, bundle});
         } catch (Exception e) {
             Log.w(TAG, "Unable to create WebApkServiceImpl.");
             e.printStackTrace();
             return null;
         }
     }
-
-    /**
-     * Gets / creates ClassLoader for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}.
-     * @param context WebAPK's context.
-     * @return The ClassLoader.
-     */
-    private static ClassLoader getClassLoaderInstance(Context context) {
-        if (sClassLoader == null) {
-            sClassLoader = createClassLoader(context);
-        }
-        return sClassLoader;
-    }
-
-    /**
-     * Creates ClassLoader for loading {@link WEBAPK_SERVICE_IMPL_CLASS_NAME}.
-     * @param context WebAPK's context.
-     * @return The ClassLoader.
-     */
-    private static ClassLoader createClassLoader(Context context) {
-        Context remoteContext = WebApkUtils.getHostBrowserContext(context);
-        if (remoteContext == null) {
-            Log.w(TAG, "Failed to get remote context.");
-            return null;
-        }
-
-        SharedPreferences preferences = context.getSharedPreferences(PREF_PACKAGE, MODE_PRIVATE);
-
-        int runtimeDexVersion = preferences.getInt(RUNTIME_DEX_VERSION_PREF, -1);
-        int newRuntimeDexVersion = checkForNewRuntimeDexVersion(preferences, remoteContext);
-        if (newRuntimeDexVersion == -1) {
-            newRuntimeDexVersion = runtimeDexVersion;
-        }
-        File localDexDir = context.getDir("dex", Context.MODE_PRIVATE);
-        if (newRuntimeDexVersion != runtimeDexVersion) {
-            Log.w(TAG, "Delete cached dex files.");
-            DexLoader.deleteCachedDexes(localDexDir);
-        }
-
-        String dexAssetName = WebApkUtils.getRuntimeDexName(newRuntimeDexVersion);
-        File remoteDexFile =
-                new File(remoteContext.getDir("dex", Context.MODE_PRIVATE), dexAssetName);
-        return DexLoader.load(remoteContext, dexAssetName, WEBAPK_SERVICE_IMPL_CLASS_NAME,
-                remoteDexFile, localDexDir);
-    }
-
-    /**
-     * Checks if there is a new "runtime dex" version number. If there is a new version number,
-     * updates SharedPreferences.
-     * @param preferences WebAPK's SharedPreferences.
-     * @param remoteContext
-     * @return The new "runtime dex" version number. -1 if there is no new version number.
-     */
-    private static int checkForNewRuntimeDexVersion(
-            SharedPreferences preferences, Context remoteContext) {
-        // The "runtime dex" version only changes when {@link remoteContext}'s APK version code
-        // changes. Checking the APK's version code is less expensive than reading from the APK's
-        // assets.
-        PackageInfo remotePackageInfo = null;
-        try {
-            remotePackageInfo = remoteContext.getPackageManager().getPackageInfo(
-                    remoteContext.getPackageName(), 0);
-        } catch (PackageManager.NameNotFoundException e) {
-            Log.e(TAG, "Failed to get remote package info.");
-            return -1;
-        }
-
-        int cachedRemoteVersionCode = preferences.getInt(REMOTE_VERSION_CODE_PREF, -1);
-        if (cachedRemoteVersionCode == remotePackageInfo.versionCode) {
-            return -1;
-        }
-
-        int runtimeDexVersion = readAssetContentsToInt(remoteContext, "webapk_dex_version.txt");
-        SharedPreferences.Editor editor = preferences.edit();
-        editor.putInt(REMOTE_VERSION_CODE_PREF, remotePackageInfo.versionCode);
-        editor.putInt(RUNTIME_DEX_VERSION_PREF, runtimeDexVersion);
-        editor.apply();
-        return runtimeDexVersion;
-    }
-
-    /**
-     * Returns the first integer in an asset file's contents.
-     * @param context
-     * @param assetName The name of the asset.
-     * @return The first integer.
-     */
-    private static int readAssetContentsToInt(Context context, String assetName) {
-        Scanner scanner = null;
-        int value = -1;
-        try {
-            scanner = new Scanner(context.getAssets().open(assetName));
-            value = scanner.nextInt();
-            scanner.close();
-        } catch (Exception e) {
-        } finally {
-            if (scanner != null) {
-                try {
-                    scanner.close();
-                } catch (Exception e) {
-                }
-            }
-        }
-        return value;
-    }
 }