安卓实现从互联网上获取图片并保存到本地目录中

因为是对互联网和内存操作，所以我们要添加如下权限:

package com.itfom.getpicfromnet;

import java.io.file;
import java.io.fileoutputstream;
import java.io.inputstream;
import java.net.httpurlconnection;
import java.net.url;

import android.annotation.suppresslint;
import android.app.activity;
import android.graphics.bitmapfactory;
import android.os.bundle;
import android.os.environment;
import android.os.handler;
import android.os.message;
import android.view.view;
import android.view.view.onclicklistener;
import android.widget.button;
import android.widget.imageview;

@suppresslint("handlerleak")
public class mainactivity extends activity {

	private imageview iv_pic;
	private button btn_get;
	@override
	protected void oncreate(bundle savedinstancestate) {
		super.oncreate(savedinstancestate);
		setcontentview(r.layout.activity_main);
		btn_get = (button) findviewbyid(r.id.btn_get);
		iv_pic = (imageview) findviewbyid(r.id.iv_img);
		//设置监听事件
		btn_get.setonclicklistener(new onclicklistener() {

			@override
			public void onclick(view v) {
				//开启子线程
				new thread(){
					public void run() {
						try {
							string urlpath = "https://pic7.nipic.com/20100607/4791134_172835008083_2.jpg";
							url url = new url(urlpath);
							httpurlconnection conn = (httpurlconnection) url.openconnection();
							conn.setconnecttimeout(6*1000);  // 注意要设置超时，设置时间不要超过10秒，避免被android系统回收
							if (conn.getresponsecode() != 200) throw new runtimeexception("请求url失败");
							inputstream insream = conn.getinputstream();
							//把图片保存到项目的根目录
							readasfile(insream, new file(environment.getexternalstoragedirectory()+"/"+"test.jpg"));
							message msg=new message();
							msg.what=0;
							handler.sendmessage(msg);
						} catch (exception e) {
							e.printstacktrace();
						}
					};
				}.start();
			}
		});
	}
	public static void readasfile(inputstream insream, file file) throws exception{
		fileoutputstream outstream = new fileoutputstream(file);
		byte[] buffer = new byte[1024];
		int len = -1;
		while( (len = insream.read(buffer)) != -1 ){
			outstream.write(buffer, 0, len);
		}
		outstream.close();
		insream.close();
	}
	//创建handler
	handler handler=new handler(){
		public void handlemessage(android.os.message msg) {
			if(msg.what==0){
				//开始绑定数据
				iv_pic.setimagebitmap(bitmapfactory.decodefile(environment.getexternalstoragedirectory()+"/test.jpg"));
			}
		};
	};
}