简单的网络请求
1 | OkHttpClient client = new OkHttpClient(); |
图片
首先得到网络的输入流，然后使用BitmapFactory将输入流转换成图片。
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2InputStream in = response.body().byteStream();
Bitmap bitmap = BitmapFactory.decodeStream(in);保存到本地。这里首先创建文件夹，然后新创建一个jpg文件，用缓冲流包装文件的输出流，最后利用图片压缩将图片写入到jpg文件中。
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22public void saveBitmap(String path,Bitmap bitmap, String fileName) {
File dirFile = new File(path);
BufferedOutputStream bos = null;
if (!dirFile.exists()) {
dirFile.mkdirs();
}
try {
File dayFile = new File(path, fileName + ".jpg");
bos = new BufferedOutputStream(new FileOutputStream(dayFile));
//图片压缩，100代表不压缩
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
bos.flush();
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}从本地读取照片。从本地读取照片是很简单的，只需要利用BitmapFactory的解析文件的方法，解析目标图片路径即可。
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Bitmap bitmap = BitmapFactory.decodeFile(file.getPath());
音频，文件下载
首先得到输入流，然后读取输入流的字节，写入到对象文件的输出流即可1
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12InputStream in = null;
OutputStream out = null;
if(response != null) {
in = response.body().byteStream();
out = new FileOutputStream(saveFile);
byte[] b = new byte[1024];
int len;
while((len = in.read(b)) != -1) {
out.write(b,0,len);
}
response.body().close();
}
断点下载文件
1 | OkHttpClient client = new OkHttpClient(); |
下面代码是实现断点下载文件的一个很重要的任务类。实现的任务有下载，暂停下载，取消下载等功能。大概流程为：查看本地保存的目的路径是否存在对应的文件，有则记录文件的大小。然后使用getContentLength（）方法来得到需要下载文件的大小。假如记录大小和实际大小相等，则证明不需要下载，如不相等则进行断点下载。RandomAccessFile的使用是因为它可以指定位置读,指定位置写的一个类,故可以实现断点下载。通常开发过程中,多用于多线程下载一个大文件.1
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134public class DownloadTask extends AsyncTask<String, Integer, Integer> {
private DownloadListener mDownListener;
private boolean isCanceled = false;
private boolean isPaused = false;
private int lastProgress;
public DownloadTask(DownloadListener downloadListener) {
mDownListener = downloadListener;
}
protected Integer doInBackground(String... strings) {
InputStream is = null;
//可读可写，在实现断点下载时优先考虑
RandomAccessFile saveFile = null;
File file = null;
try {
long downloadedLength = 0; //记录已下载的文件长度
String downloadUrl = strings[0];
String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
file = new File(directory + fileName);
if (file.exists()) {
downloadedLength = file.length();
}
long contentLength = getContentLength(downloadUrl); //实际文件长度
if (contentLength == 0) {
return Constants.TYPE_FAILED;
} else if (contentLength == downloadedLength) {
return Constants.TYPE_SUCCESS;
}
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
//断点下载，指定从哪个字节开始下载
.addHeader("RANGE", "bytes=" + downloadedLength + "-")
.url(downloadUrl)
.build();
Response response = client.newCall(request).execute();
if (response != null) {
is = response.body().byteStream();
saveFile = new RandomAccessFile(file, "rw");
saveFile.seek(downloadedLength); //跳过已下载的字节
byte[] b = new byte[1024];
int total = 0;
int len;
while ((len = is.read(b)) != -1) {
if (isCanceled) {
return Constants.TYPE_CANCELED;
} else if (isPaused) {
return Constants.TYPE_PAUSED;
} else {
total += len;
saveFile.write(b, 0, len);
int progress = (int) ((total + downloadedLength) * 100 / contentLength);
publishProgress(progress);
}
}
response.body().close();
return Constants.TYPE_SUCCESS;
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (is != null) {
is.close();
}
if (saveFile != null) {
saveFile.close();
}
if (isCanceled && file != null) {
file.delete();
}
} catch (Exception e) {
e.printStackTrace();
}
}
return Constants.TYPE_FAILED;
}
public void onProgressUpdate(Integer... values) {
int progress = values[0];
if (progress > lastProgress) {
mDownListener.onProgress(progress);
lastProgress = progress;
}
}
protected void onPostExecute(Integer status) {
switch (status) {
case Constants.TYPE_SUCCESS:
mDownListener.onSuccess();
break;
case Constants.TYPE_FAILED:
mDownListener.onFailed();
break;
case Constants.TYPE_PAUSED:
mDownListener.onPaused();
break;
case Constants.TYPE_CANCELED:
mDownListener.onCanceled();
break;
default:
break;
}
}
public void pauseDownload(){
isPaused= true;
}
public void cancelDownload(){
isCanceled = true;
}
private long getContentLength(String downloadUrl) throws IOException {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(downloadUrl)
.build();
Response response = client.newCall(request).execute();
if (response != null && response.isSuccessful()) {
long contentLength = response.body().contentLength();
response.body().close();
return contentLength;
}
return 0;
}
}