android从网络获取图片以及异步加载图片

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Environment;
import android.util.Log;
import android.widget.ImageView;

/**
* 处理图片的工具类
*/
public class ImageUtils {

/**
* 图片基准路径
*/
private static final String BASE_SDCARD_IMAGES = "/mnt/sdcard/demo/images/";

private static final String TAG = "ImageUtils";

/**
* 判断文件是否存在
*
* @param 文件在本地的完整名
* @return
*/
private static boolean judgeExists(String fullName) {

File file = new File(fullName);

return file.exists();
}

/**
* 获取最后的‘/’后的文件名
*
* @param name
* @return
*/
private static String getLastName(String name) {
int lastIndexOf = 0;
try {
lastIndexOf = name.lastIndexOf('/');
} catch (Exception e) {
e.printStackTrace();
}
return !name.equals("") ? name.substring(lastIndexOf + 1) : "";
}

/**
* 拼接一个完整的本地文件名
* @param 文件的网络路径
* @return
*/
private static String getImageFullName(String name) {
return BASE_SDCARD_IMAGES + getLastName(name);
}

/**
* 通过该网络路径获取Bitmap
* @param 该图片的网络路径
*/
public static Bitmap getBitmap(String urlPath) {

Bitmap bitmap = null;
String fullName = getImageFullName(urlPath);
if (ImageUtils.judgeExists(fullName)) {
/* 存在就直接使用 */
Log.e(TAG, "使用了sdcard里的图片");
bitmap = BitmapFactory.decodeFile(fullName);
} else {
/* 去下载图片,下载完成之后返回该对象 */
Log.e(TAG, "去下载了图片");
bitmap = downloadAndSaveBitmap(urlPath, fullName);
}
return bitmap;
}

/**
* 下载保存图片
*
* @param urlPath
*            下载路径
* @param fullName
*            文件保存路径+文件名
* @return
*/
private static Bitmap downloadAndSaveBitmap(String urlPath, String fullName) {

Bitmap bitmap = downloadImage(urlPath);

/* 首先判断是否挂载了sdcard */
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {

if (bitmap != null) {

saveBitmap(fullName, bitmap);

}
} else {
Log.e(TAG, "没有sdcard无法保存图片");
}

return bitmap;
}

/**
* 保存图片
*
* @param fullName
* @param bitmap
*/
private static void saveBitmap(String fullName, Bitmap bitmap) {

if (bitmap != null) {

try {
File file = new File(fullName);
if (!file.exists()) {
creatFolder(fullName);
file.createNewFile();
}
FileOutputStream fos = new FileOutputStream(file);
bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);
fos.flush();
} catch (IOException e) {
e.printStackTrace();
Log.e(TAG, "图片保存失败，异常信息是：" + e.toString());
}
} else {
Log.e(TAG, "没有下载成功图片，无法保存");
}
}

/**
* 创建保存文件的文件夹
*
* @param fullName
*            带文件名的文件路径
* @return
*/
private static void creatFolder(String fullName) {
if (getLastName(fullName).contains(".")) {
String newFilePath = fullName.substring(0, fullName
.lastIndexOf('/'));
File file = new File(newFilePath);
file.mkdirs();
}
}

/**
* 下载图片
*
* @param urlPath
* @return
*/
private static Bitmap downloadImage(String urlPath) {

try {
byte[] byteData = getImageByte(urlPath);
if (byteData == null) {
Log.e(TAG, "没有得到图片的byte，问题可能是path：" + urlPath);
return null;
}
int len = byteData.length;

BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.RGB_565;
options.inPurgeable = true;
options.inInputShareable = true;
options.inJustDecodeBounds = false;
if (len > 200000) {// 大于200K的进行压缩处理
options.inSampleSize = 2;
}

return BitmapFactory.decodeByteArray(byteData, 0, len);
} catch (Exception e) {
e.printStackTrace();
Log.e(TAG, "图片下载失败，异常信息是：" + e.toString());
return null;
}
}

/**
* 获取图片的byte数组
*
* @param urlPath
* @return
*/
private static byte[] getImageByte(String urlPath) {
InputStream in = null;
byte[] result = null;
try {
URL url = new URL(urlPath);
HttpURLConnection httpURLconnection = (HttpURLConnection) url
.openConnection();
httpURLconnection.setDoInput(true);
httpURLconnection.connect();
if (httpURLconnection.getResponseCode() == 200) {
in = httpURLconnection.getInputStream();
result = readInputStream(in);
in.close();
} else {
Log
.e(TAG, "下载图片失败，状态码是："
+ httpURLconnection.getResponseCode());
}
} catch (Exception e) {
Log.e(TAG, "下载图片失败，原因是：" + e.toString());
e.printStackTrace();
} finally {
Log.e(TAG, "下载图片失败!");
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return result;
}

/**
* 将输入流转为byte数组
*
* @param in
* @return
* @throws Exception
*/
private static byte[] readInputStream(InputStream in) throws Exception {

ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
while ((len = in.read(buffer)) != -1) {
baos.write(buffer, 0, len);
}
baos.close();
in.close();
return baos.toByteArray();

}

/**
* 此方法用来异步加载图片
* @param imageview
* @param path
*/
public static void downloadAsyncTask(final ImageView imageview,
final String path) {
new AsyncTask<String, Void, Bitmap>() {

@Override
protected Bitmap doInBackground(String... params) {
return getBitmap(path);
}

@Override
protected void onPostExecute(Bitmap result) {
super.onPostExecute(result);
if (result != null && imageview != null) {
imageview.setImageBitmap(result);
} else {
Log.e(TAG, "在downloadAsyncTask里异步加载图片失败！");
}
}

}.execute(new String[] {});

}

}