package com.example.day7_practise;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

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.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.Toast;

public class MainActivity extends Activity{

ImageView iv;

Button btn1;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

iv=(ImageView) findViewById(R.id.imageView1);

btn1=(Button) findViewById(R.id.btn1);

btn1.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

DownloadTask mTask = new DownloadTask();

String uri = "https://ss0.bdstatic.com/5aV1bjqh_Q23odCf/static/superman/img/logo/logo_white_fe6da1ec.png";

mTask.execute(uri);

}

});

}

private class DownloadTask extends AsyncTask<String,Integer , Bitmap> {

ProgressDialog pDialog;

/**

* 参数1为doInBackground参数 由onClick方法中execute设置的参数

* 参数2为onProgressUpdate参数 由publishProgress（方法用在子线程中）传入。

* 参数3为onPostExecute参数 由doInBackground方法返传入

*/

// (主线程)在子线程执行之前调用它

@Override

protected void onPreExecute() {

//创建对话框

pDialog = new ProgressDialog(MainActivity.this);

//创建标题栏

pDialog.setTitle("下载图片");

//设置进度条样式

pDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);

pDialog.setMax(100);

pDialog.setMessage("正在下载");

pDialog.show();

}

// (子线程)执行子线程

@Override

protected Bitmap doInBackground(String... params) {

HttpURLConnection conn = null;

URL url;

try {

url = new URL(params[0]);

conn=(HttpURLConnection) url.openConnection();

int code=conn.getResponseCode();

if(code==200){

//取出流中图片信息解析成图片

Bitmap bmap=BitmapFactory.decodeStream(conn.getInputStream());

return bmap;

}else {

throw new RuntimeException("网络访问失败");

}

} catch (MalformedURLException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}finally {

if(conn!=null){

conn.disconnect();

conn=null;

}

}

return null;

}

// (主线程)在子线程执行时更新UI界面

@Override

protected void onProgressUpdate(Integer... values) {

//pDialog.setProgress(value);

}

// (主线程)在子线程执行之后执行，擦屁股专用

@Override

protected void onPostExecute(Bitmap bmap) {

if(bmap==null){

Toast.makeText(MainActivity.this, "下载失败", 0).show();

}else {

iv.setImageBitmap(bmap);

}

pDialog.cancel();

}

}

}