【Android】Async异步任务之添加进度条

上一个blog实现了图片下载功能，但没有实现进度条，这里我们加上这个功能。

首先，将三个泛型参数的第二个改为Integer，表示进度条的刻度为int

public class MyTask extends AsyncTask<String, Integer, Bitmap>

然后，修改doInBackground方法如下：
@Override
protected Bitmap doInBackground(String... params) {
// TODO Auto-generated method stub
// 完成对图片的下载
Bitmap bitmap = null;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
InputStream inputStream = null;
try {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(params[0]);
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
inputStream = httpResponse.getEntity().getContent();
// 先获得文件的长度
long file_length = httpResponse.getEntity()
.getContentLength();
int len = 0;
byte[] data = new byte[1024];
int total_length = 0;

while (-1 != (len = inputStream.read(data, 0, 1024))) {
total_length += len;
int value = (int) ((total_length / (float) file_length) * 100);
//向onPrgressUpdate传递参数
publishProgress(value);
outputStream.write(data, 0, len);
}
byte[] result = outputStream.toByteArray();
bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);
}
} catch (Exception e) {
// TODO: handle exception
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return bitmap;
}

主要是修改了进度条的参数
最后在onProgressUpdate中加入：

dialog.setProgress(values[0]);

这行代码主要是处理上面的函数中publishProgress穿过来的参数。