Android_AsyncTask_DownloadImg_progressDIalog

<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_downloadimg_prgress;

import java.io.ByteArrayOutputStream;
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.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
/**
 *
        //弹出进度条对话框基本使用
        //创建进度条对话框
        ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
        //设置标题
        progressDialog.setTitle("正在下载");
        //设置内容
        progressDialog.setMessage("下载中");
        //设置弹出对话框显示的样式
        progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        //显示
        progressDialog.show();
        //给进度条设置值,在show()之后设置
        progressDialog.setProgress(50);
        //隐藏
        progressDialog.hide();
 *
 *
 */
/**注意:需要在清单文件中添加网络权限
 * 1.初始化控件,数据
 * 2.设置下载点击事件
 *     2.1.开启异步任务下载图片
 *         1.先显示对话框,进度为0
 *         2.开始下载
 *             1.获得文件大小
 *             2.获得当前下载的总量
 *             3.计算当前百分比
 *             4.通知对话框更新更改进度(主线程)
 *             5.下载完成,返回数据
 *         3.下载完成
 *             1.关闭对话框
 *             2.显示下载成功的图片
 * @author my
 *
 */
public class MainActivity extends Activity {

    private ImageView image;
    private static final String imgPath = "http://c.hiphotos.baidu.com/image/h%3D200/sign=8cbc53a04ded2e73e3e9812cb700a16d/f7246b600c338744513e9358560fd9f9d72aa01f.jpg";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        image = (ImageView) findViewById(R.id.image);
    }
    public void onDownLoadImg(View v){
        new MyAsyncTask().execute(imgPath);
    }
    class MyAsyncTask extends AsyncTask<String, Integer, Bitmap>{
        private ProgressDialog progressDialog;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressDialog = new ProgressDialog(MainActivity.this);
            progressDialog.setTitle("正在下载");
            progressDialog.setMessage("下载中...");
            progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            progressDialog.show();

        }
        @Override
        protected Bitmap doInBackground(String... params) {
            try {
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(params[0]);
                HttpResponse response = httpClient.execute(httpGet);
                if(200 == response.getStatusLine().getStatusCode()){
                    //获得实体对象
                    HttpEntity entity = response.getEntity();
                    //得到输入流
                    InputStream is = entity.getContent();
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();
                    //获得要下载图片的总长度
                    long contentLength = entity.getContentLength();
                    //当前下载图片的长度
                    int currentLength = 0;
                    byte[] buf = new byte[50];
                    int len = 0;
                    while(-1 !=(len = is.read(buf))){
                        currentLength += len;
                        //计算当前的百分比
                        int percent =(int) ((currentLength/(float)contentLength)*100);
                        //通知调用主线程的方法更新进度,自动调用onProgressUpdate()方法
                        publishProgress(percent);
                        //写到流中
                        baos.write(buf, 0, len);
                        baos.flush();
                    }
                    is.close();
                    baos.close();
                    //把字节流转换成字节数组
                    byte[] byteArray = baos.toByteArray();
                    //把字节流转换成Bitmap
                    Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
                    return bitmap;
                }
            } 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);
            //关闭对话框
            progressDialog.dismiss();
            if(result != null){
                image.setImageBitmap(result);
            }else{
                Toast.makeText(MainActivity.this, "网络错误", 0).show();
            }

        }
        //在主线程中执行,参数类型与类定义泛型的第二个参数一致
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
            //更新进度
            progressDialog.setProgress(values[0]);
        }
    }

}