How to implement pull down refresh in android?

Currently I am working on a fragment that simply a webview with framelayout, the problem is, I would like to do something like the pull down refresh ( just like some refresh function common of list view ). Assume there is a `refreshToDo()` function , all I need is just a layout (when I drag the body it show the refresh header, when the header at the certain height, it call `refreshToDo()` , when I release it , it go back to top and hide) , but how to implement that? thanks layout: (It contains the main content and target content, you can simply ingore target content, it is for playing the video in fullscreen in webview): ``` <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" > <FrameLayout android:id="@+id/main_content" android:layout_width="match_parent" android:layout_height="match_parent" > <WebView android:id="@+id/webView" android:layout_width="match_parent" android:layout_height="match_parent" /> </FrameLayout> <FrameLayout android:id="@+id/target_view" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@android:color/black" android:visibility="gone" > </FrameLayout> </RelativeLayout> ``` Fragment: ``` public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.web_fragment, container, false); mTargetView = (FrameLayout) rootView.findViewById(R.id.target_view); mContentView = (FrameLayout) rootView.findViewById(R.id.main_content); mWebView = (WebView) rootView.findViewById(R.id.webView); mWebView.setVerticalScrollBarEnabled(false); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) { WebView.setWebContentsDebuggingEnabled(true); } if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) mWebView.getSettings().setAllowUniversalAccessFromFileURLs(true); mWebView.setWebViewClient(new MyWebViewClient(getActivity())); mWebView.setWebChromeClient(new MyWebChromeClient(getActivity())); mWebView.getSettings().setDomStorageEnabled(true); mWebView.getSettings().setPluginState(WebSettings.PluginState.ON); mWebView.getSettings().setJavaScriptEnabled(true); mWebView.addJavascriptInterface(this, "jsinterface"); // default go to video page mWebView.loadUrl("file://" + getActivity().getFilesDir().toString() + StorageUtils.finalfoldername.toString() + "video_list.html"); return rootView; } ``` How to add the custom view to implement the pull down refresh? Thanks