Hi Friends,
Here is the next part of my blog. Here I am going to discuss about the important things today. Every project will starts with a splash in first page. So let’s discuss about the splash.
Splash Screen
We need to display the logo at the middle of the screen, whatever the screen mode it may be. So in order to handle this we will use the below XML file.
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@color/white"> <ImageView android:id="@+id/ImageView01" android:scaleType="center" android:layout_height="fill_parent" android:layout_width="fill_parent" android:layout_centerInParent="true" android:src="@drawable/sun"> </ImageView> </LinearLayout> |
In the above XML file we have a layout with an ImageView which is centered in parent, without stretching it completely to its parent. Here according to the background of the logo we need to change the background color of the layout. Here it is “@color/White” in the above example. These colors will be maintained in project\res\values\color.xml folder. We can add new colors, which are needed for our project over there. That’s it, our layout is ready now. Let’s go to source.
There is a class named Handler in android which will be going to handle the assigned work to do after some particular time. You may already know that we can start the Activities by using the Intents, we will start the activity after a period of splashTime as shown below.
new Handler().postDelayed(new Runnable(){ public void run() { startActivity(new Intent(MainActivity.this, MainMenu.class)); finish(); } }, _splashTime); |
Finally we are moving to the main menu from splash. The whole above process works perfectly if and only if the logo doesn’t have designs and different colors on the background screen. If you have different kinds of logo with lot of background colors then let’s go for the second option.
Here we need to prepare two images of splash one is for portrait and another is for landscape. Create a xml file in the folder project\res\layout-land\menu.xml with the same name in the layout folder. According to the screen mode the xml files will be used. But don’t forget to maintain the same names just like in \layout folder.
If we want Fade-in or fade-out effects for our splash then we need to create xml files with desired effects as shown below and need to place it in \anim folder.
<?xml version="1.0" encoding="utf-8"?> <set> <alpha xmlns:android="http://schemas.android.com/apk/res/android" android:interpolator="@android:anim/accelerate_interpolator" android:fromAlpha="0.0" android:toAlpha="1.0" android:duration="1000" /> </set> |
fromAlpha, toAlpha and duration will be used according to your requirements. If we change the values fromAlpha to toAlpha then we will get fadeout effect.
The total source with Fadein and Fadeout effects can be downloaded from below link.
You can download the project with source from here. or You can download the project with source from here.
Customizing List, Connecting Internet, XML Parsing,Downloading Images, Updating the User Interface Images at Runtime, Handling UI without specifying height and width of any view in the layout
Connecting to the internet
We have two methods in connecting the internet server.
1. Get
2. Post
In first method as you already know all the values will be appended to the url . In the second (Post) method we will send the data separately which is secured. I am going to give both the methods to connect the net.
1)Get Method
private InputStream openHttpConnection(String urlStr) { InputStream in = null; int resCode = -1; try { Log.d("openHttpConnection", "URL:"+urlStr); URL url = new URL(urlStr); URLConnection urlConn = url.openConnection();//Opening Connection if (!(urlConn instanceof HttpURLConnection)) { throw new IOException ("URL is not an Http URL"); } Log.d("openHttpConnection", "httpConn:1"); HttpURLConnection httpConn = (HttpURLConnection)urlConn; httpConn.setAllowUserInteraction(false); httpConn.setInstanceFollowRedirects(true); httpConn.setRequestMethod("GET"); httpConn.setRequestProperty("User-Agent", "Mozilla/5.0 (X11; U; Linux "+"i686; en-US; rv:1.8.1.6) Gecko/20061201 Firefox/2.0.0.6 (Ubuntu-feisty)"); httpConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); Log.d("openHttpConnection", "setting requests and properties"); httpConn.connect(); Log.d("openHttpConnection", "Connected successfully"); resCode = httpConn.getResponseCode(); Log.d("openHttpConnection", "resCode"+resCode); if (resCode == HttpURLConnection.HTTP_OK) { in = httpConn.getInputStream(); Log.d("openHttpConnection", "Fetchinf data done"); } } catch (MalformedURLException e) { e.printStackTrace(); Log.d("openHttpConnection", "1"+e); } catch (IOException e) { e.printStackTrace(); Log.d("openHttpConnection", ""+e); } return in; } |
The above code will connect to the specific site and will get the response and the data in the form of InputStream. The variable resCode will get the response from the server. The value should be 200 i.e., HttpURLConnection.HTTP_OK otherwise we have some problem with server.
2)Post Method:
This method will send the data separately .The code is as shown below.This method needs two strings. One is for URL and the other is for the data which we want to post the data.
private InputStream postPage(String url, String data) { InputStream is = null; ret = null; httpClient.getParams().setParameter(ClientPNames.COOKIE_POLICY, CookiePolicy.RFC_2109); httpPost = new HttpPost(url); response = null; StringEntity tmp = null; httpPost.setHeader("User-Agent", "Mozilla/5.0 (X11; U; Linux " + "i686; en-US; rv:1.8.1.6) Gecko/20061201 Firefox/2.0.0.6 (Ubuntu-feisty)"); httpPost.setHeader("Accept", "text/html,application/xml," + "application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"); httpPost.setHeader("Content-Type", "application/x-www-form-urlencoded"); try { tmp = new StringEntity(data,"UTF-8"); } catch (UnsupportedEncodingException e) { System.out.println("HTTPHelp : UnsupportedEncodingException : "+e); } httpPost.setEntity(tmp); try { response = httpClient.execute(httpPost,localContext); } catch (ClientProtocolException e) { System.out.println("HTTPHelp : ClientProtocolException : "+e); } catch (IOException e) { System.out.println("HTTPHelp : IOException : "+e); } ret = response.getStatusLine().toString(); HttpEntity he = response.getEntity(); try { InputStream inStream = he.getContent(); is = inStream; } catch (IllegalStateException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return is; } |
Downloading Images
Lets discuss about downloading the images. Here we have some issues with google api. Some times this is throwing decoder->decode returned false. For this I am also trying. 95% it wont come. Most of the cases it works well and code is as shown below.
public Drawable downloadDrawable(String imageUrl) { try { Log.d("downloadDrawable", "Starting Connection"); URL url = new URL(imageUrl); URLConnection conn = url.openConnection(); conn.connect(); Log.d("downloadDrawable", "Connection Created Successfully"); InputStream is = conn.getInputStream(); Log.d("downloadDrawable", "InputStream created Successfully"); d = Drawable.createFromStream(is, url.toString()); Log.d("downloadDrawable", "Drawable created Successfully"); is.close(); } catch (IOException e) { Log.d("ERROR3", "Ex::"+e); } return d; } |
Updating UI at Runtime after completion of the downloading Image using AsyncTask
This is very important one in Android. Normally in the other Technologies we will download the images using a separate Thread. But here if we use the same separate thread then it will create issue at the time of setting the image to the ImageView.
Android doesn’t support updating the UI in a separate thread. So, we cannot create a separate thread for updating the UI with images after downloading it. So, Inorder to handle this Android is having a class named AsyncTask. This really helps us a lot. The code is as shown below.
Calling AsyncTask
try { DownloadFilesTask d = new DownloadFilesTask(); d.execute(new URL(bookImageUrl));//url of the image d.sendObjectImageView(iv_logo);// This is the object to which the image //has to set } catch (Exception e) e.printStackTrace(); } |
AsyncTask Code
This Class will take care of downloading the image. This is not only for downloading. If we want to know whenever the work completed to it then chose this. The method onPostExecute method will be called by the Asynctask then we can do what ever we want to do after completion of that work. Here we need to set the image to the object that we got from the method sendObjectImageView.
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { ImageView iv; int id; protected Long doInBackground(URL... urls) { int count = urls.length; long totalSize = 0; downloadDrawable(urls[0].toString()); return totalSize; } public void sendObjectImageView(ImageView ivLogo) { // TODO Auto-generated method stub this.iv = ivLogo; id = -1; } public void sendObjectImageView(ImageView iv,int id) { // TODO Auto-generated method stub this.iv = iv; this.id = id; } protected void onProgressUpdate(Integer... progress) { Log.d("DownloadFilesTask", "onProgressUpdate"+progress[0]); } protected void onPostExecute(Long result) { Log.d("DownloadFilesTask", "onPostExecute"+result); if(d!=null && iv!=null) { iv.setImageDrawable(d); if(id!=-1) booksImagesList[id] = d; } } |
XML Parsing
The description of these things will be displayed soon. until then check out the project.
Layout Handling
The description of these things will be displayed soon. until then check out the project.
Customizing Lists
The description of these things will be displayed soon. until then check out the project.
You can download the project source from here or You can download the project source from here
