本篇文章给大家分享的是有关Android开发中怎么实现一个图片下载功能，小编觉得挺实用的，因此分享给大家学习，希望大家阅读完这篇文章后可以有所收获，话不多说，跟着小编一起来看看吧。
1.普通的下载方式
布局文件：
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:src="@drawable/icon" android:layout_width="wrap_content" android:id="@+id/imgPic" android:layout_gravity="center|center_vertical" android:layout_height="fill_parent"> </ImageView> </LinearLayout>
java文件
public class DownloadImage extends Activity {
private ImageView imgPic;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.download_image);
imgPic = (ImageView) findViewById(R.id.imgPic);
String url = "http://ww1.sinaimg.cn/bmiddle/6834c769jw1djjf4p3p9rj.jpg";
loadRmoteImage(url);
}
/**
* @param imgUrl
* 远程图片文件的URL
*
* 下载远程图片
*/
private void loadRmoteImage(String imgUrl) {
URL fileURL = null;
Bitmap bitmap = null;
try {
fileURL = new URL(imgUrl);
} catch (MalformedURLException err) {
err.printStackTrace();
}
try {
HttpURLConnection conn = (HttpURLConnection) fileURL
.openConnection();
conn.setDoInput(true);
conn.connect();
InputStream is = conn.getInputStream();
int length = (int) conn.getContentLength();
if (length != -1) {
byte[] imgData = new byte[length];
byte[] buffer = new byte[512];
int readLen = 0;
int destPos = 0;
while ((readLen = is.read(buffer)) > 0) {
System.arraycopy(buffer, 0, imgData, destPos, readLen);
destPos += readLen;
}
bitmap = BitmapFactory.decodeByteArray(imgData, 0,
imgData.length);
}
} catch (IOException e) {
e.printStackTrace();
}
imgPic.setImageBitmap(bitmap);
}2.带进度条的下载
有时候网络差，或者是图片太大，会出现黑屏的情况，用户体验比较差，那么增加一个进度条是提高用户体验的好方法
/**
* @author xushilin xsl xushilin@kingtoneinfo.com
* @version： 创建时间：2011-7-27 下午02:55:56
* 说 明: android中下载图片
* 修改历史：
*/
public class DownloadImage extends Activity {
private ImageView imgPic;
private ProgressBar progressBar;
private int totalSize=0;
private int size=0;
private Handler mHandler;
String url = "http://ww1.sinaimg.cn/bmiddle/6834c769jw1djjf4p3p9rj.jpg";
private Bitmap bitmap=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.download_image);
imgPic = (ImageView) findViewById(R.id.imgPic);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
progressBar.setProgress(getProgressInt(progressBar.getMax()));
mHandler = new Handler() {
public void handleMessage(Message msg) {
progressBar.setProgress(getProgressInt(progressBar.getMax()));
if(bitmap!=null){
imgPic.setImageBitmap(bitmap);
}
}
};
new Thread(){
public void run(){
loadRmoteImage(url);
}
}.start();
}
/**
* @param imgUrl
* 远程图片文件的URL
*
* 下载远程图片
*/
private void loadRmoteImage(String imgUrl) {
URL fileURL = null;
try {
fileURL = new URL(imgUrl);
} catch (MalformedURLException err) {
err.printStackTrace();
}
try {
HttpURLConnection conn = (HttpURLConnection) fileURL
.openConnection();
conn.setDoInput(true);
conn.connect();
InputStream is = conn.getInputStream();
int length = (int) conn.getContentLength();
totalSize=length;
if (length != -1) {
byte[] imgData = new byte[length];
byte[] buffer = new byte[512];
int readLen = 0;
int destPos = 0;
while ((readLen = is.read(buffer)) > 0) {
System.arraycopy(buffer, 0, imgData, destPos, readLen);
destPos += readLen;
size=destPos;
mHandler.sendEmptyMessage(1);
Thread.sleep(100);
}
bitmap = BitmapFactory.decodeByteArray(imgData, 0,
imgData.length);
mHandler.sendEmptyMessage(1);
}
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private int getProgressInt(int max) {
int result = (totalSize > 0) ? (int) (size * max * 1.0 / totalSize) : 0;
return result;
}
}以上就是Android开发中怎么实现一个图片下载功能，小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注亿速云行业资讯频道。
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