1.新建android工程asyncloadpicture
新建布局文件activity_main.xml主界面为一个gridview，还有其子项布局文件gridview_item.xml
2.功能主界面mainactivity.java,主代码如下
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package com.example.asyncloadpicture;import java.util.arraylist;import android.app.activity;import android.content.context;import android.graphics.bitmap;import android.graphics.bitmapfactory;import android.os.asynctask;import android.os.bundle;import android.widget.gridview;/*** @author ymw* @data --*/public class mainactivity extends activity {private gridview gridviewimg;private arraylist<imageentity> imagelist = new arraylist<imageentity>();@overrideprotected void oncreate(bundle savedinstancestate) {super.oncreate(savedinstancestate);setcontentview(r.layout.activity_main);gridviewimg = (gridview) findviewbyid(r.id.gridviewimg);initdata();}private void initdata() {for (int i = ; i < ; i++) {imageentity b = new imageentity();b.setimage(bitmapfactory.decoderesource(getresources(),r.drawable.nopicture));imagelist.add(b);}imageadapter adapter = new imageadapter(getapplicationcontext(),imagelist);gridviewimg.setadapter(adapter);string[] params = {"http://images.cnitblog.com/i///.png","p" };new imageloadtask(getapplicationcontext(), adapter).execute(params);}/** 图片异步加载类 */public class imageloadtask extends asynctask<string, void, void> {private imageadapter adapter;public imageloadtask(context context, imageadapter adapter) {this.adapter = adapter;}@overrideprotected void doinbackground(string... params) {string url = params[];// 获取传来的参数，图片uri地址string p = params[];for (int i = ; i < adapter.getcount(); i++) {imageentity bean = (imageentity) adapter.getitem(i);bitmap bitmap = bitmapfactory.decodestream(request.handlerdata(url));bean.setimage(bitmap);publishprogress(); // 通知去更新ui}return null;}public void onprogressupdate(void... voids) {if (iscancelled())return;// 更新uiadapter.notifydatasetchanged();}}/** 图片实体 */public class imageentity {private bitmap image;public bitmap getimage() {return image;}public void setimage(bitmap image) {this.image = image;}}} |
3.gridview列表图片适配器代码imageadapter.java
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package com.example.asyncloadpicture;import java.util.arraylist;import android.content.context;import android.view.layoutinflater;import android.view.view;import android.view.viewgroup;import android.widget.baseadapter;import android.widget.imageview;import com.example.asyncloadpicture.mainactivity.imageentity;/*** * @author ymw* @data -- 图片适配器*/public class imageadapter extends baseadapter {private context _context;private arraylist<imageentity> _list;public imageadapter(context context, arraylist<imageentity> imagelist) {this._context = context;this._list = imagelist;}@overridepublic int getcount() {return _list.size();}@overridepublic object getitem(int position) {return _list.get(position);}@overridepublic long getitemid(int position) {return position;}@overridepublic view getview(int position, view convertview, viewgroup parent) {layoutinflater inflater = layoutinflater.from(_context);convertview = inflater.inflate(r.layout.gridview_item, null);imageview imgview = (imageview) convertview.findviewbyid(r.id.imgview);imageentity b = _list.get(position);// 如果有图片则读取，没有则跳过if (b.getimage() != null) {imgview.setimagebitmap(b.getimage());}return convertview;}} |
4.请求网络读取图片的类request.java
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package com.example.asyncloadpicture;import java.io.ioexception;import java.io.inputstream;import java.net.url;import java.net.urlconnection;import android.graphics.drawable.drawable;import android.util.log;/*** 工具类，主要根据url读取图片返回流的方法* * @author ymw* */public class request {public static inputstream handlerdata(string url) {inputstream instream = null;try {url feedurl = new url(url);urlconnection conn = feedurl.openconnection();conn.setconnecttimeout( * );instream = conn.getinputstream();} catch (exception e) {e.printstacktrace();}return instream;}/** 直接返回drawable对象设置图片 */public static drawable loadimagefromnetwork(string imageurl) {drawable drawable = null;try {// 可以在这里通过文件名来判断，是否本地有此图片drawable = drawable.createfromstream(new url(imageurl).openstream(), "image.jpg");} catch (ioexception e) {log.d("test", e.getmessage());}if (drawable == null) {log.d("test", "null drawable");} else {log.d("test", "not null drawable");}return drawable;}} |
以上内容给大家介绍了android 中使用 asynctask 异步读取网络图片的相关知识，希望对大家有所帮助！
