안드로이드 풀소스 안에 있습니다.

packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallAppProgress.java

    108         if((installFlags & PackageManager.REPLACE_EXISTING_PACKAGE )!= 0) {
    109             Log.w(TAG, "Replacing package:"+mAppInfo.packageName);
    110         }
    111         PackageInstallObserver observer = new PackageInstallObserver();
    112         pm.installPackage(mPackageURI, observer, installFlags);

제가 짯던 예제 소스입니다.

public class APKInstall extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        File apkFile = new File("/sdcard/FileBrowser.apk");
        Uri apkUri = Uri.fromFile(apkFile);
        Log.i("APKInstall", "Set apk path");

        try {
         Intent intent = new Intent(Intent.ACTION_VIEW);
         intent.setDataAndType( Uri.fromFile(apkFile), "application/vnd.android.package-archive");
         startActivity(intent);
         Log.i("APKInstall", "APK installed");
  } catch (Exception e) {
   // TODO: handle exception
   Log.i("APKInstall", e.getMessage());
  }

//        PackageManager pm = getPackageManager();
//        pm.installPackage(apkUri);
    }
}