Android_AsyncTask_DownloadImg

layout.xml

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >

    <ImageView
        android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher"
        android:maxHeight="300dp"
        android:maxWidth="300dp"
        android:adjustViewBounds="true"/>
    <Button 
        android:id="@+id/btn_download"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onDownLoadImg"
        android:text="点击下载图片"
        android:textSize = "20sp"/>

</LinearLayout>

main.java

package com.example.day07_asynctask_downloadimg;

import java.io.IOException;
import java.io.InputStream;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.view.View;
import android.widget.ImageView;

/*
 * 下载图片:
 * 1.初始化控件
 * 2.设置下载图片按钮监听
 *     2.1创建一个异步任务类,实现其抽象方法
 *     2.2开启异步任务开始下载
 *         在子线程中进行进行耗时操作下载图片
 *             1)创建HttpCient对象
 * `        2)创建HttpGet对象传入
 *             3)执行请求获得HttpResponse对象
 *             4)获得响应码
 *             5)判断响应码,成功,获得实体对象httpEntity
 *             6)通过HttpEntity对象的getContent()方法得到读取流
 *             7)封装成BitMap对象,并传回给主线程
 *         在主线程中显示图片
 * 
 *             
 */
public class MainActivity extends Activity {

    private ImageView image;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        image = (ImageView) findViewById(R.id.image);
        
    }
    //2.设置下载图片按钮监听
    public void onDownLoadImg(View v){
        //new MyAsyncTask().execute("http://c.hiphotos.baidu.com/image/h%3D200/sign=8cbc53a04ded2e73e3e9812cb700a16d/f7246b600c338744513e9358560fd9f9d72aa01f.jpg");

    }
//     2.1创建一个异步任务类,实现其抽象方法
    class MyAsyncTask extends AsyncTask<String, Void, Bitmap>{

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
        @Override
        protected Bitmap doInBackground(String... params) {
            try {
                DefaultHttpClient defaultCLient = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(params[0]);
                HttpResponse response = defaultCLient.execute(httpGet);
                int code = response.getStatusLine().getStatusCode();
                if(code == 200){
                    HttpEntity entity = response.getEntity();
                    InputStream content = entity.getContent();
                    Bitmap result = BitmapFactory.decodeStream(content);
                    return result;
                }
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return null;
        }
        @Override
        protected void onPostExecute(Bitmap result) {
            super.onPostExecute(result);
            image.setImageBitmap(result);
        }

        
    }

}