android根据包名打开另一个app的两种方法

第一种：
private void doStartApplicationWithPackageName(String packagename) {

   // 通过包名获取此APP详细信息，包括Activities、services、versioncode、name等等
   PackageInfo packageinfo = null;
   try {
      packageinfo = mContext.getPackageManager().getPackageInfo(packagename, 0);
   } catch (PackageManager.NameNotFoundException e) {
      e.printStackTrace();
   }
   if (packageinfo == null) {
      return;
   }

   // 创建一个类别为CATEGORY_LAUNCHER的该包名的Intent
   Intent resolveIntent = new Intent(Intent.ACTION_MAIN, null);
   resolveIntent.addCategory(Intent.CATEGORY_LAUNCHER);
   resolveIntent.setPackage(packageinfo.packageName);

   // 通过getPackageManager()的queryIntentActivities方法遍历
   List<ResolveInfo> resolveinfoList = mContext.getPackageManager()
         .queryIntentActivities(resolveIntent, 0);

   ResolveInfo resolveinfo = resolveinfoList.iterator().next();
   if (resolveinfo != null) {
      // packagename = 参数packname
      String packageName = resolveinfo.activityInfo.packageName;
      // 这个就是我们要找的该APP的LAUNCHER的Activity[组织形式：packagename.mainActivityname]
      String className = resolveinfo.activityInfo.name;
      // LAUNCHER Intent
      Intent intent = new Intent(Intent.ACTION_MAIN);
      intent.addCategory(Intent.CATEGORY_LAUNCHER);

      // 设置ComponentName参数1:packagename参数2:MainActivity路径
      ComponentName cn = new ComponentName(packageName, className);

      intent.setComponent(cn);
      startActivity(intent);
   }
}

来源：http://blog.csdn.net/mad1989/article/details/38090513

第二种：

Intent intent = getPackageManager().getLaunchIntentForPackage(packname);
startActivity(intent);