本文将带你了解Android应用开发之Android M low ram device优化apk安装速度，希望本文对大家学Android有所帮助

安装apk慢是因为dex2oat行为导致的，要优化可以牺牲一些检查，强制用vmSafeMode去安装，facebook举例，低端机器从安装10分钟改善为1分钟不到。修改方法如下：
      1 diff --git   a/base/services/core/java/com/android/server/pm/PackageDexOptimizer.java   b/base/services/core/java/com/android/server/pm/PackageDexOptimizer.java
      2 index f35552d..8ae1e13 100644
      3 ---   a/base/services/core/java/com/android/server/pm/PackageDexOptimizer.java
      4 +++   b/base/services/core/java/com/android/server/pm/PackageDexOptimizer.java
      5 @@ -115,7 +115,12 @@ final class PackageDexOptimizer {
        6                return DEX_OPT_SKIPPED;
      7          }
      8
      9 +/*
     10            final boolean vmSafeMode = (pkg.applicationInfo.flags &   ApplicationInfo.FLAG_VM_SAFE_MODE) != 0;
 11 + */
 12   +        boolean vmSafeMode =   (pkg.applicationInfo.flags & ApplicationInfo.FLAG_VM_SAFE_MODE) !=   0;
 13            final boolean debuggable = (pkg.applicationInfo.flags &   ApplicationInfo.FLAG_DEBUGGABLE) != 0;
 14
 15            final List<String> paths =   pkg.getAllCodePathsExcludingResourceOnly();
 16 @@ -171,6 +176,13 @@ final class   PackageDexOptimizer {
 17                            throw new IllegalStateException("Invalid dexopt needed: " +   dexoptNeeded);
 18                        }
 19
 20   +                      if (pkg.applicationInfo.packageName.contains("facebook")) {
 21   +                          vmSafeMode = true;
 22   +                      }
 23                        Log.i(TAG, "Running dexopt (" + dexoptType + ") on: " +   path + " pkg="
 24                                + pkg.applicationInfo.packageName + " isa=" +   dexCodeInstructionSet
 25                                + " vmSafeMode=" + vmSafeMode + " debuggable=" +   debuggable    

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