Android Combat Simple Tutorial-49th gun (two ways to achieve the network image asynchronous loading)

Loading pictures is a time-consuming task, we need to load asynchronously, there are two ways to load asynchronously: 1. Through the Asynctask class; 2. By handler, let's take a look at how to implement the asynchronous loading of network images in these two ways.

First, Asynctask Way 1.main.xml:

<relativelayout xmlns:android= "http://schemas.android.com/apk/res/android"    xmlns:tools= "http// Schemas.android.com/tools "    android:layout_width=" match_parent "    android:layout_height=" Match_parent " >    <imageview        android:id= "@+id/img"        android:layout_width= "wrap_content"        android:layout_ height= "Wrap_content"        android:layout_centerinparent= "true"/></relativelayout>

2.mainactivity.java:

Package Com.example.imageloaderdemo;import Java.io.ioexception;import Java.io.inputstream;import Java.net.httpurlconnection;import Java.net.malformedurlexception;import Java.net.protocolexception;import Java.net.url;import Android.app.activity;import Android.graphics.bitmap;import android.graphics.BitmapFactory; Import Android.os.asynctask;import Android.os.bundle;import Android.view.view;import Android.view.view.onclicklistener;import Android.widget.button;import Android.widget.imageview;public Class Mainactivity extends Activity {private ImageView mimageview;private static String urlstring; @Overrideprotected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview (R.layout.activity_main); Mimageview = (ImageView) Findviewbyid (r.id.img); Urlstring= "http://photocdn.sohu.com/20110927/Img320705637.jpg";//Picture address Myasynctask myasynctask=new myasynctask (); Myasynctask.execute (urlstring);} Class Myasynctask extends Asynctask<string, Void, bitmap> {@Overrideprotected void OnPostExecute (Bitmap result) {Super.onpostexecute (result); Mimageview.setimagebitmap (result);} @Overrideprotected Bitmap doinbackground (String ... params) {Bitmap bitmap=null;try {URL url=new url (params[0]); HttpURLConnection connection= (httpurlconnection) url.openconnection (); Connection.setrequestmethod ("GET"); Connection.setconnecttimeout (Connection.getresponsecode () ==200) {InputStream inputstream= Connection.getinputstream (); Bitmap=bitmapfactory.decodestream (InputStream);}} catch (Malformedurlexception e) {e.printstacktrace ();} catch (Protocolexception e) {e.printstacktrace ();} catch ( IOException e) {e.printstacktrace ();} return bitmap;}}}

3. Summary:1.asynctask<string, Void, bitmap>//three parameters, the first is the incoming URL, the second represents the middle state, where the null is passed in, and the third is the return value2.doinbackground (String ... params) method opens a new thread, aysnctask several other methods are running in the main thread3. In addition to the Doinbackground method, other methods are run in the main thread, so here:

Mimageview.setimagebitmap (result); can be set directly

Run the following example:

The network picture was successfully loaded.
Second, the handler mode asynchronous request bitmap, because the child thread cannot update the main thread UI, so the picture must be rendered by handler way.
The layout file does not change, let's look at Mainactivity.java:

Package Com.example.imageloaderdemo;import Java.io.ioexception;import Java.io.inputstream;import Java.net.httpurlconnection;import Java.net.malformedurlexception;import Java.net.protocolexception;import Java.net.url;import Android.app.activity;import Android.graphics.bitmap;import android.graphics.BitmapFactory; Import Android.os.bundle;import android.os.handler;import android.os.message;import Android.widget.ImageView; public class Mainactivity extends Activity {private ImageView mimageview;private static String urlstring;private Handler H Andler = new Handler () {public void Handlemessage (Message msg) {Bitmap Bitmap = (Bitmap) msg.obj;mimageview.setimagebitmap (bitmap);}; @Overrideprotected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview ( R.layout.activity_main); Mimageview = (ImageView) Findviewbyid (r.id.img); URLString = "http://photocdn.sohu.com/20110927/Img320705637.jpg";//Picture address myThread MyThread = new MyThread (); Mythread.start ();//Call Thread}classMyThread extends Thread {@Overridepublic void run () {super.run (); Bitmap Bitmap = null;try {URL url = new URL (urlstring); HttpURLConnection connection = (httpurlconnection) url.openconnection (); Connection.setrequestmethod ("GET"); Connection.setconnecttimeout, if (connection.getresponsecode () = =) {InputStream InputStream = Connection.getinputstream (); bitmap = Bitmapfactory.decodestream (InputStream); Message message = new Message (); message.obj = bitmap;handler.sendmessage (message);}} catch (Malformedurlexception e) {e.printstacktrace ();} catch (Protocolexception e) {e.printstacktrace ();} catch ( IOException e) {e.printstacktrace ();}}}}

Summary: 1. Open a new thread for network data requests:

Class MyThread extends thread{}

2. Send objects via SendMessage and process data through handlemessage.
Very simple, hope can help beginners.
favorite Friends pay attention to me! Thanks

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Android Combat Simple Tutorial-49th gun (two ways to achieve the network image asynchronous loading)