我对Android非常陌生,并且需要制作一个应用程序,该应用程序需要下载并缓存使用的url中的jpg文件。OutputStream问题... OutofBoundsException
我已经从多个引用(和我自己的修修补补)这么远到这一点:
public class download_image extends AsyncTask<String, Void, String> {
int count;
@Override
protected String doInBackground(String... urls) {
try {
String root = getFilesDir().toString();
URL imgurl = new URL(urls[0]); // Form a URL object from string.
URLConnection c = imgurl.openConnection(); //Open connection.
int length_of_file = c.getContentLength(); // Get size of target jpg
Log.v("Background Response","Length fo target img = "+length_of_file);
InputStream i = new BufferedInputStream(imgurl.openStream(),length_of_file);
//Make target image file...
final File image = new File(getApplicationContext().getCacheDir().toString(),"image.jpg");
OutputStream o = new FileOutputStream(image);
byte data[] = new byte[length_of_file];
long total = 0;
while ((count = i.read(data))!=1){
total+=count;
o.write(data,0,count);
}
o.flush();
o.close();
i.close();
} catch (MalformedURLException m) {
Log.e("Exception", m.toString());
} catch (IOException i) {
Log.e("Exception", i.toString());
}
return null;
}
@Override
protected void onPostExecute(String s) {
System.out.println("Downloaded");
super.onPostExecute(s);
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
}
这个问题似乎是数组数据[]过流或东西吗? 我不太明白。我已经尝试使InputStream的缓冲区等于来自length_of_file = getContentLength()的文件大小;
任何帮助将不胜感激! 到目前为止,相当高兴地发现了其他问题(比如让内部文件夹写入以及Async Task是什么......我原来不知道我需要HTTPConnections)。
08-04 15:51:22.938 13454-13486/com.example.johnny.fibre V/Background Response: Length fo target img = 106620
08-04 15:51:23.058 13454-13486/com.example.johnny.fibre E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #2
Process: com.example.johnny.fibre, PID: 13454
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:325)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:761)
Caused by: java.lang.ArrayIndexOutOfBoundsException: length=106620; regionStart=0; regionLength=-1
at java.util.Arrays.checkOffsetAndCount(Arrays.java:4857)
at libcore.io.IoBridge.write(IoBridge.java:490)
at java.io.FileOutputStream.write(FileOutputStream.java:316)
at com.example.johnny.fibre.Home$download_image.doInBackground(Home.java:476)
at com.example.johnny.fibre.Home$download_image.doInBackground(Home.java:456)
at android.os.AsyncTask$2.call(AsyncTask.java:305)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:761)
谢谢。我会查找ByteArrayOutputStream并返回,如果我有任何问题。 我想缓存图像以备将来使用,而不是每次需要图像时都不得不使用活动的Internet套接字...因此Helper Utilities似乎已经停用。 – Jcov
如果使用我引用的帮助程序实用程序,则可以在初始化时或第一次需要时进行联机调用,然后在本地模型中存储对映像的引用,以便不必查询网络。 –