android 中通过包名去启动其他的acticity

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 = 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 = 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);
}
}