android-下载保存网络图片并显示下载进度条

1.显示进度条

2.启动耗时的网络图片现在程序（线程）并发送消息

3.Handler根据消息判断下载进度并更新UI.

主程序：

package com.tangzq;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import android.app.Activity;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.ProgressBar;

import android.widget.TextView;

public class Download_Progressbar extends Activity implements OnClickListener {

private static final String LOG_TAG="Download_Progressbar";

String imgHttp1="http://cdn.androidcommunity.com/wp-content/uploads/2011/03/Playbook_android_apps.jpg";

private TextView txt;

private Button downImg;

private ImageView imgView;

private ProgressBar progressBar;

private Bitmap bitmap;

private static final int LOADING=1;

private static final int END=2;

int maxSize=0;

int nowSize=0;

Handler handler;

private static final String SDCARD="/sdcard/";

private String fileName="networkimg1.png";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.download_progressbar);

txt=(TextView)findViewById(R.id.txt);

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

downImg.setOnClickListener(this);

imgView=(ImageView)findViewById(R.id.imgView);

progressBar=(ProgressBar)findViewById(R.id.progressBar);

//progressBar.setVisibility(View.GONE);

handler=new Handler(){

@Override

public void handleMessage(Message msg) {

//super.handleMessage(msg);

if(null!=progressBar){

//设置进度条最大值

progressBar.setMax(maxSize);

//当前已经下载的值

nowSize+=msg.getData().getInt("loadingSize");

//设置进度条的当前进度值

progressBar.setProgress(nowSize);

if(msg.what==LOADING){

//显示已经下载的值

txt.setText("已下载："+(nowSize*100)/maxSize+"%");

Log.e("Download_Progressbar", "正在下载："+nowSize);

}

if(msg.what==END){

//下载完成后隐藏进度条

progressBar.setVisibility(View.INVISIBLE);

//显示图片

imgView.setImageBitmap(bitmap);

//将图片保存到sdcard中

saveImg(SDCARD+fileName,bitmap);

//结束当前线程

Thread.currentThread().interrupt();

}

}

}

};

}

@Override

public void onClick(View paramView) {

//首先清空图片和进度条

if(null!=bitmap){

imgView.setImageBitmap(null);

nowSize=0;

progressBar.setProgress(0);

txt.setText("即将下载......");

}

//1、显示进度条

progressBar.setVisibility(View.VISIBLE);

//2、开始下载

new MyThread(imgHttp1).start();

}

//保存图片方法

public void saveImg(String fullPath,Bitmap bitmap){

File file=new File(fullPath);

if(file.exists()){

file.delete();

}

try {

FileOutputStream fos=new FileOutputStream(file);

boolean isSaved=bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);

if(isSaved){

fos.flush();

fos.close();

}

Log.e(LOG_TAG, "文件保存成功");

} catch (FileNotFoundException e) {

Log.e(LOG_TAG, "保存失败");

e.printStackTrace();

} catch (IOException e) {

Log.e(LOG_TAG, "保存失败");

e.printStackTrace();

}

}

class MyThread extends Thread{

String httpImg;

public MyThread(String httpImg){

this.httpImg=httpImg;

}

@Override

public void run() {

//super.run();

ByteArrayOutputStream bos=new ByteArrayOutputStream();

try {

URL url=new URL(httpImg);

HttpURLConnection con=(HttpURLConnection)url.openConnection();

con.setDoInput(true);

con.connect();

InputStream is=con.getInputStream();

//获取文件的大小

maxSize=con.getContentLength();

byte []buffer=new byte[1024];

int len=-1;

while((len=is.read(buffer))!=-1){

bos.write(buffer,0,len);

bos.flush();

//发送消息

Message msg=new Message();

msg.what=LOADING;

Bundle bundle=new Bundle();

bundle.putInt("loadingSize", len);

msg.setData(bundle);

Thread.sleep(100);

handler.sendMessage(msg);

}

//关闭输入流

is.close();

//关闭连接

con.disconnect();

byte []imgBytes=bos.toByteArray();

bitmap=BitmapFactory.decodeByteArray(imgBytes, 0, imgBytes.length);

//下载结束后发送消息

Message msg=new Message();

msg.what=END;

handler.sendMessage(msg);

} catch (MalformedURLException e) {

Log.e("Download_Progressbar", "MalformedURLException");

e.printStackTrace();

} catch (IOException e) {

Log.e("Download_Progressbar", "IOException");

e.printStackTrace();

} catch (InterruptedException e) {

Log.e("Download_Progressbar", "InterruptedException");

e.printStackTrace();

}

}

}

}

download_progressbar.xml代码：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="一步下载图片"

android:id="@+id/txt"/>

<Button

android:id="@+id/downImg"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="开始下载图片" />

<FrameLayout

android:layout_width="match_parent"

android:layout_height="wrap_content" >

<ImageView

android:id="@+id/imgView"

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

<ProgressBar

android:id="@+id/progressBar"

android:layout_width="fill_parent"

style="?android:attr/progressBarStyleHorizontal"

android:layout_height="wrap_content"

android:layout_gravity="center"

android:visibility="invisible"

/>

</FrameLayout>

</LinearLayout>

截图：

http://hi.baidu.com/tzq668766/item/e0ce2d0f99b86e8d02ce1b0f