下载带有asyncTask的映像

Question

我正在尝试加强我对asyncTask的了解，所以我按照教程下载了一个图像，但我不明白，我得到了一个错误的ArrayOutofBound索引，所以如果有人告诉我原因这里是代码，请告诉我为什么他迭代进度条最大

    public class MainActivity extends AppCompatActivity {
           ProgressBar progessBar;
           ImageView MyImage;
           private final String IMAGE_URL =    "http://www.101apps.co.za/images/headers/101_logo_very_small.jpg";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    MyImage = findViewById(R.id.imageView);
    ImageButton downloaad = findViewById(R.id.imageButton);
    downloaad.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            new downloadFile(MainActivity.this).execute(IMAGE_URL);
        }
    });

}
public class downloadFile extends AsyncTask<String , Integer , String>{
    private  int PROGRESS_BAR_MAX = 100;
    Context context;
    public downloadFile(Context cxt){
         this.context = cxt;
    }
    @Override
    protected String doInBackground(String... strings) {
        String result = "";
        String path = context.getFilesDir() + File.pathSeparator + "downloadFile.png";
        HttpURLConnection httpURLConnection = null;
        try{
            final URL url  = new URL(strings[0]);
            httpURLConnection = (HttpURLConnection) url.openConnection();
            int length = httpURLConnection.getContentLength();
            InputStream IS = (InputStream) url.getContent();
            byte[] imageData = new byte[length];
            Log.d("aho" , "" + length);
            int buffersize = (int) Math.ceil(length/(double)PROGRESS_BAR_MAX);
            int download = 0;
            for(int i = 1 ; i < PROGRESS_BAR_MAX ; i++){
                long read = IS.read(imageData , download , buffersize);
                download += read;
                publishProgress(i);

            }

            BufferedInputStream bufferedReader = new BufferedInputStream(httpURLConnection.getInputStream());
            FileOutputStream Fo = new FileOutputStream(path);
            int data = bufferedReader.read();
            while(data != -1){
                Fo.write(data);
                data = bufferedReader.read();
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(httpURLConnection == null){
                httpURLConnection.disconnect();
            }
        }
        publishProgress(PROGRESS_BAR_MAX);
        return path;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progessBar = findViewById(R.id.progressBar);
        progessBar.setMax(PROGRESS_BAR_MAX);


    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
        progessBar.setProgress(values[0]);
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        if(s != null) {
            progessBar.setVisibility(View.INVISIBLE);
            Bitmap bitmap = BitmapFactory.decodeFile(s);
            MyImage.setImageBitmap(bitmap);

        }
    }
}
}

下面是堆栈跟踪01-20 03:37:40.607 407 5-4096/com.gamecodeschool.bodybuilder E/AndroidRuntime：致命异常：AsyncTask#1进程:com.gamecodeschool.bodybuilder，PID:4075 java.lang.RuntimeException：在Android.os.AsyncTask$3执行doInBackground（）时出错。done(AsyncTask.java:353)在java.util.concurrent.FutureTask.FinishCompletion（futureTask.java:383)在FferedSource.java:368)在com.gamecodeschool.bodybuilder.MainActivity$DownloadFile.DoinBackgroun(mainActivity.java:66)在com.gamecodeschool.bodybuilder.MainActivity$DownloadFile.DoinBackgroun(mainActivity.java:45)在android.os.AsyncTask$2。调用(asynctask.java:333)在java.util.concurrent.FutureTask.Run（FutureTask.java:266)

Answer 1

这是因为您的read循环是在进度计数上循环，而不是在下载的资源大小上循环。循环访问资源的大小（确保检查读取错误），并根据读取的数量与总长度计算进度。