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.getExternalStorageState() == Environment.MEDIA_MOUNTED) {

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[] {});

}

}