网络获取图片

package com.itheima.image;import android.app.Activity;import android.app.ProgressDialog;import android.graphics.Bitmap;import android.os.Bundle;import android.os.Handler;import android.view.View;import android.widget.EditText;import android.widget.ImageView;public class MainActivity extends Activity {private EditText pathET;private NetService service;private ImageView picIV;private Handler handler = new Handler();@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);picIV = (ImageView) findViewById(R.id.picIV);pathET = (EditText) findViewById(R.id.pathET);service = new NetService(getCacheDir());}public void go(View v) {final ProgressDialog dialog = new ProgressDialog(this);dialog.setCancelable(false);// 设置进度条不能被取消dialog.show();// 显示进度条new Thread() {public void run() {try {String path = pathET.getText().toString().trim();// 获取路径final Bitmap bm = service.getImage(path);// 访问网络, 获取图片handler.post(new Runnable() {// 给主线程发送一个Runnablepublic void run() {picIV.setImageBitmap(bm);// 主线程设置图片dialog.dismiss();}});} catch (Exception e) {e.printStackTrace();}}}.start();}}

package com.itheima.image;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLEncoder;import android.graphics.Bitmap;import android.graphics.BitmapFactory;public class NetService {private File cacheDir;public NetService(File cacheDir) {this.cacheDir = cacheDir;}public Bitmap getImage(String path) throws Exception {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setConnectTimeout(5000);// 设置超时时间, 连接网络的时候, 如果超过5000毫秒没有响应, 就抛出异常File file = new File(cacheDir, URLEncoder.encode(path, "UTF-8"));if (file.exists()) {// 判断缓存文件是否存在conn.setIfModifiedSince(file.lastModified());// 如果存在, 就设置请求头: 最后修改时间}int code = conn.getResponseCode();System.out.println(code);if (code == 200) {InputStream in = conn.getInputStream();// 获取输入流ByteArrayOutputStream out = new ByteArrayOutputStream();byte[] buffer = new byte[8192];int length;while((length = in.read(buffer)) != -1) // 从网络读取数据out.write(buffer, 0, length);// 把数据写到内存in.close();out.close();byte[] data = out.toByteArray();// 获取内存中的所有数据FileOutputStream fos = new FileOutputStream(file);fos.write(data);// 把图片数据写到本地, 作为缓存(推荐在新线程中操作, 用户感受会更好)fos.close();Bitmap bm = BitmapFactory.decodeByteArray(data, 0, data.length);// 把字节数据解码为Bitmap return bm;} else if (code == 304) {return BitmapFactory.decodeFile(file.getAbsolutePath());// 读取本地文件, 创建一个Bitmap}throw new RuntimeException("网络出错: " + code);}}

<uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

<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"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <Button        android:id="@+id/goBT"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentRight="true"        android:onClick="go"        android:text="Go" />    <EditText        android:id="@+id/pathET"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignBaseline="@id/goBT"        android:layout_toLeftOf="@id/goBT"        android:hint="请输入要访问的地址"        android:inputType="textUri"        android:text="http://192.168.1.228:8080/05.Web/a.jpg" />    <ImageView        android:id="@+id/picIV"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_below="@id/pathET"        android:layout_marginTop="10dp" /></RelativeLayout>