AsyncTask实现下载图片

实现效果：

 

 

 

/*采用异步任务  AsyncTask<String,Integer, byte[]>
  * 参数一代表 执行异步任务时传递的参数的类型
  * 参数二 如果不采用进度，则填Void,否则填 Integer
  * 参数三 是指网络回传回来的数据类型
  */

 

客户端代码：

MainActivity.java

  1 package com.example.load_jpg;
  2 
  3 import java.io.ByteArrayOutputStream;
  4 import java.io.InputStream;
  5 
  6 import org.apache.http.HttpResponse;
  7 import org.apache.http.client.HttpClient;
  8 import org.apache.http.client.methods.HttpGet;
  9 import org.apache.http.impl.client.DefaultHttpClient;
 10 
 11 import android.app.Activity;
 12 import android.app.ProgressDialog;
 13 import android.content.Context;
 14 import android.graphics.Bitmap;
 15 import android.graphics.BitmapFactory;
 16 import android.os.AsyncTask;
 17 import android.os.Bundle;
 18 import android.view.View;
 19 import android.view.View.OnClickListener;
 20 import android.widget.Button;
 21 import android.widget.ImageView;
 22 import android.widget.Toast;
 23 
 24 public class MainActivity extends Activity {
 25 
 26     
 27     private ProgressDialog dialog;
 28     private ImageView iv;
 29     private Button btn;
 30     private final  static  String PATH="http://172.16.30.146:8080/Phone/a10.jpg";
 31     private Context context;
 32     
 33     @Override
 34     protected void onCreate(Bundle savedInstanceState) {
 35         super.onCreate(savedInstanceState);
 36         setContentView(R.layout.activity_main);
 37         context = this;
 38         init();
 39         btn.setOnClickListener(new OnClickListener() {
 40             @Override
 41             public void onClick(View v) {
 42                 new MyTask().execute(PATH);//执行异步任务
 43             }
 44         });
 45     }
 46     private void init() {
 47         iv  =(ImageView) findViewById(R.id.image);
 48         btn = (Button) findViewById(R.id.btn);
 49         dialog = new ProgressDialog(context);
 50         dialog.setCancelable(true);
 51         dialog.setTitle("提醒");
 52         dialog.setMessage("正在下载中...");
 53         dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
 54     }
 55 
 56     public class MyTask extends AsyncTask<String, Integer, byte[]>{
 57 
 58         @Override
 59         protected void onPreExecute() {//在异步符务执行之前 这个方法会被执行
 60             dialog.show();
 61             super.onPreExecute();
 62         }
 63         
 64         @Override
 65         protected byte[] doInBackground(String... params) {
 66             HttpClient httpClient = new DefaultHttpClient();
 67             HttpGet httpGet = new HttpGet(params[0]);
 68             
 69             InputStream is = null;
 70             ByteArrayOutputStream bos =new ByteArrayOutputStream();
 71             
 72             try {
 73                 HttpResponse httpResponse = httpClient.execute(httpGet);//执行path
 74                 if(httpResponse.getStatusLine().getStatusCode()==200){
 75                     is = httpResponse.getEntity().getContent();
 76                     
 77                     long total_length = httpResponse.getEntity().getContentLength();
 78                     int current_length = 0;
 79                     byte[] tmp = new byte[1024];
 80                     int len;
 81                     while((len=is.read(tmp))!=-1){
 82                         current_length+=len;
 83                         int update = (int)((float)current_length/total_length*100);
 84                         publishProgress(update);
 85                         bos.write(tmp, 0, len);
 86                     }
 87                     return bos.toByteArray();
 88                     
 89                 }
 90             } catch (Exception e) {
 91                 
 92             }finally{
 93                 httpClient.getConnectionManager().shutdown();
 94             }
 95             
 96             return null;
 97         }
 98         
 99         @Override
100         protected void onProgressUpdate(Integer... values) {
101             dialog.setProgress(values[0]);
102             super.onProgressUpdate(values);
103         }
104         
105         @Override
106         protected void onPostExecute(byte[] result) {
107             if(result!=null){
108                 Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);
109                 iv.setImageBitmap(bitmap);
110                 Toast.makeText(context, "下载成功", Toast.LENGTH_LONG).show();
111             }else{
112                 Toast.makeText(context, "下载失败", Toast.LENGTH_LONG).show();
113             }
114             dialog.dismiss();
115             super.onPostExecute(result);
116         }
117         
118     }
119 
120 }


activity_main.xml

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5    android:orientation="vertical"
 6     tools:context=".LoadPicActivity" >
 7 
 8     
 9     <ImageView
10         android:id="@+id/image"
11         android:layout_width="300dp"
12         android:layout_height="300dp"
13         android:src="@drawable/ic_launcher"
14         />
15     
16  <Button 
17      android:id="@+id/btn"
18        android:layout_width="match_parent"
19         android:layout_height="wrap_content"
20         android:text="下载"
21      
22      />
23 </LinearLayout>


服务器端：建立web project，放入图片即可

 

最后在清单里注册：<uses-permission android:name="android.permission.INTERNET"/>

 

posted @ 2016-03-15 12:45  UniqueColor  阅读(343)  评论(0)  编辑  收藏  举报