android中的http通讯（2）

功能：通过网络请求下载一张图片到本地展示

在AndroidManifest.xml文件中添加权限：

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

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

xml布局文件

<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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout><strong>
</strong>

MainActivity.java文件

package com.example.dd;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.ImageView;
public class MainActivity extends Activity {
private ImageView contentImageView;
private Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
new HttpConnection("http://h.hiphotos.baidu.com/image/pic/item/6c224f4a20a446239e8d311c9b22720e0cf3d70d.jpg",contentImageView,handler).start();
}

private void init(){
contentImageView = (ImageView)findViewById(R.id.imageView1);
}
}

HttpConnection.java文件

package com.example.dd;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.os.Handler;
import android.webkit.WebView;
import android.widget.ImageView;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
* Created by xiaoyuer on 2015/11/13.
*/
public class HttpConnection extends Thread{
private String mUrl;
private ImageView mImageView;
private Handler mHandler;
HttpConnection(String Url,ImageView imageView,Handler Handler)
{
this.mUrl = Url;
this.mImageView = imageView;
this.mHandler = Handler;
}
@Override
public void run()
{
try {
//构建url对象
URL httpUrl = new URL(mUrl);
//通过openConnection方法打开一个HttpURLConnection对象
HttpURLConnection conn = (HttpURLConnection)httpUrl.openConnection();
//设置请求超时，访问网页时可能没给我们应答，设置超时等待时间
conn.setReadTimeout(5000);
//设置访问请求方式
conn.setRequestMethod("GET");

//获得图片信息的输入流
conn.setDoInput(true);
InputStream in = conn.getInputStream();

//先把图片下载到本地
FileOutputStream out = null;
File downloadFile = null;
//把当前的时间设置为文件名，valueOf()把long类型转换为String类型
String fileName = String.valueOf(System.currentTimeMillis());

//如果sd卡有加载
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
{
//获得sd卡的根目录
File parent = Environment.getExternalStorageDirectory();
//创建目录
downloadFile= new File(parent,fileName);
out = new FileOutputStream(downloadFile);
}

//创建缓冲区(2个字节大小)
byte[] b = new byte[2*1024];
int length;
if(out != null){
while((length = in.read(b)) != -1){
out.write(b,0,length);
}
}

final Bitmap bitmap = BitmapFactory.decodeFile(downloadFile.getAbsolutePath());
//读出文件之后，通过handler去更新UI
mHandler.post(new Runnable() {
@Override
public void run() {
//把已经下载来图片的bitmap传递进来
mImageView.setImageBitmap(bitmap);
}
});

}catch(MalformedURLException e){
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}
}
}

效果图：



已经把美女图下载下来