package com.example.android_asynctask_downloadimage;

 import java.io.ByteArrayOutputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import org.apache.http.HttpResponse;

 import org.apache.http.client.HttpClient;

 import org.apache.http.client.methods.HttpGet;

 import org.apache.http.impl.client.DefaultHttpClient;

 import android.app.Activity;

 import android.app.ProgressDialog;

 import android.graphics.Bitmap;

 import android.graphics.BitmapFactory;

 import android.os.AsyncTask;

 import android.os.Bundle;

 import android.view.Menu;

 import android.view.View;

 import android.widget.Button;

 import android.widget.ImageView;

 /**

  * @author xiaowu

  * NOTE:异步任务AsyncTask

  */

 public class MainActivity extends Activity {

     private Button button ;

     private Button button2 ;

     private ImageView imageView ;

     private final String IMAGE_PATH ="http://e.hiphotos.baidu.com/zhidao/pic/item/c2fdfc039245d68858f1c69fa5c27d1ed21b241d.jpg";

     private ProgressDialog progressDialog ;

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.activity_main);

         button = (Button) this.findViewById(R.id.button1);

         progressDialog = new ProgressDialog(MainActivity.this);

         progressDialog.setTitle("提示");

 //        progressDialog.setCancelable(false);

         progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

         progressDialog.setMessage("正在下载图片，请耐心等待...");

         imageView = (ImageView) this.findViewById(R.id.imageView1);

         button.setOnClickListener(new View.OnClickListener() {

             @Override

             public void onClick(View v) {

                 // TODO Auto-generated method stub

                 new MyTask().execute(IMAGE_PATH);

             }

         });

     }

     /**

      * @author xiaowu

      * 异步任务AsyncTask，执行网络下载图片

      * AsyncTask<String,  Integer, byte[]>    如果异步任务不需要参数传递，可以直接将参数设置为Void

      *      params:

      *         String：（网络图片的）路径

      *         Integer: 进度单位，刻度类型

      *         byte[]：异步任务执行的返回结果

      * 异步任务有4个步骤：

      *         1、onPreExecute();    在异步任务执行之前执行，用来构建一个异步任务，如显示一个进度条给用户看

      *          2、doInBackground(Params...);    异步任务必须实现的方法,具体的异步任务所做的事情

      *        3、onProgressUpdate(Progress...);

      *      4、onPostExecute(Result);

      */

     public class MyTask extends AsyncTask<String,  Integer, byte[]>{

         //在异步任务执行之前执行，用来构建一个异步任务，如显示一个进度条给用户看

         @Override

         protected void onPreExecute() {

             // TODO Auto-generated method stub

             super.onPreExecute();

             //展示进度条对话框

             progressDialog.show();

         }

         //异步任务必须实现的方法,具体的异步任务所做的事情。并将结果返回值最后一个步骤。

         @Override

         protected byte[] doInBackground(String... params) {

             // TODO Auto-generated method stub

             //

             HttpClient httpClient = new DefaultHttpClient();

             HttpGet httpGet = new HttpGet(params[0]);

             InputStream inputStream = null;

             byte[] result = null;    //图片的所有内容

             ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

             try {

                 //发起get请求，并获取反馈

                 HttpResponse httpResponse = httpClient.execute(httpGet);

                 long file_length = httpResponse.getEntity().getContentLength();    //文件实际总长度

                 int total_length = 0 ;

                 byte[] data = new byte[1024];

                 int len = 0 ;

                 if (httpResponse.getStatusLine().getStatusCode()==200) {

 //                    result = EntityUtils.toByteArray(httpResponse.getEntity());

                     //读取返回内容（内容是以流的形式返回）

                     inputStream = httpResponse.getEntity().getContent();

                     //更新进度条并读取数据

                     while ((len = inputStream.read(data)) != -1) {

                         total_length +=len ;

                         int progress_value = (int) ((total_length/ (float) file_length)*100);

                         //通过publishProgress（）方法发布进度值到onProgressUpdate

                         publishProgress(progress_value);    //发布刻度单位

                         byteArrayOutputStream.write(data, 0, len);

                     }

                 }

                 result = byteArrayOutputStream.toByteArray();

             }catch (IOException e) {

                 // TODO Auto-generated catch block

                 e.printStackTrace();

             }finally{

                 //关连接

                 httpClient.getConnectionManager().shutdown();

             }

             return result;

         }

         //更新UI展示信息：如进度条的变动

         @Override

         protected void onProgressUpdate(Integer... values) {

             // TODO Auto-generated method stub

             super.onProgressUpdate(values);

             progressDialog.setProgress(values[0]);

         }

         //将doInBackground的执行结果展示到UI

         @Override

         protected void onPostExecute(byte[] result) {

             // TODO Auto-generated method stub

             super.onPostExecute(result);

             Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);

             imageView.setImageBitmap(bitmap);

             progressDialog.dismiss();

         }

     }

     @Override

     public boolean onCreateOptionsMenu(Menu menu) {

         // Inflate the menu; this adds items to the action bar if it is present.

         getMenuInflater().inflate(R.menu.main, menu);

         return true;

     }

 }