我通过管理位图来学习下载图像。我使用BitmapFactory:options.inJustDecodeBounds下载图像。当我使用此声明时，
Bitmap bitmap = BitmapFactory.decodeStream(in) - 确实有效。
但是，当我使用样本大小并试图计算时，它不下载。我用过这样的东西：
public Bitmap downloadUrlToStream(String urlString, final ImageView imageView) {
HttpURLConnection urlConnection = null;
BufferedInputStream in = null;
try {
final URL url = new URL(urlString);
urlConnection = (HttpURLConnection) url.openConnection();
in = new BufferedInputStream(urlConnection.getInputStream(), IO_BUFFER_SIZE);
return decodeSampledBitmapFromResource(200,200,in);
} catch (final IOException e) {
Log.e(TAG, "Error in downloadBitmap - " + e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
try {
if (in != null) {
in.close();
}
} catch (final IOException e) {
}
}
return null; }
public static Bitmap decodeSampledBitmapFromResource(int reqWidth, int reqHeight, InputStream is) {
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(is, null, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
options.inJustDecodeBounds = false;
return BitmapFactory.decodeStream(is, null, options);
}
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// BEGIN_INCLUDE (calculate_sample_size)
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value that is a power of 2 and
// keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
// This offers some additional logic in case the image has a strange
// aspect ratio. For example, a panorama may have a much larger
// width than height. In these cases the total pixels might still
// end up being too large to fit comfortably in memory, so we should
// be more aggressive with sample down the image (=larger
// inSampleSize).
long totalPixels = width * height / inSampleSize;
// Anything more than 2x the requested pixels we'll sample down
// further
final long totalReqPixelsCap = reqWidth * reqHeight * 2;
while (totalPixels > totalReqPixelsCap) {
inSampleSize *= 2;
totalPixels /= 2;
}
}
return inSampleSize;
// END_INCLUDE (calculate_sample_size)
}
calculateSamplesize（）方法是否存在问题。是不行啊？
答案 0 :(得分：0)
我建议你使用另一种方式，就像魅力：Android查询。
您可以从此处下载该jar文件：http://code.google.com/p/android-query/downloads/list
AQuery androidAQuery=new AQuery(this);
举个例子：
androidAQuery.id(YOUR IMAGEVIEW).image(YOUR IMAGE TO LOAD, true, true, getDeviceWidth(), ANY DEFAULT IMAGE YOU WANT TO SHOW);
使用上面的代码，您可以直接通过网址显示您的图片。现在下面的代码是从url：
直接获取Bitmap androidAQuery.ajax(YOUR IMAGE URL,Bitmap.class,0,new AjaxCallback<Bitmap>(){
@Override
public void callback(String url, Bitmap object, AjaxStatus status) {
super.callback(url, object, status);
//You will get Bitmap from object.
}
});
此库由Android本身提供，因此请使用它并查看您想要的结果。
它非常快速和准确，使用它你可以在加载时找到更多的功能，如动画，如果需要，可以获得位图等。
答案 1 :(得分：0)
您可以使用Universal imageLoader下载和调整位图大小，这是示例代码，
protected ImageLoader imageLoader = ImageLoader.getInstance();
DisplayImageOptions options;
options = new DisplayImageOptions.Builder().resetViewBeforeLoading()
.cacheOnDisc().imageScaleType(ImageScaleType.IN_SAMPLE_INT)
.bitmapConfig(Bitmap.Config.RGB_565)
.displayer(new FadeInBitmapDisplayer(100)).build();
imageLoader.init(ImageLoaderConfiguration.createDefault(getActivity()));
imageLoader.displayImage(
<Image_URL>,
<Image_view>, options, new ImageLoadingListener() {
@Override
public void onLoadingComplete(String imageUri,
View view, Bitmap loadedImage) {
<Image_view>.setImageBitmap(resizedBitmap(loadedImage,200,200));
}
@Override
public void onLoadingStarted(String imageUri, View view) {
// TODO Auto-generated method stub
}
@Override
public void onLoadingFailed(String imageUri, View view,
FailReason failReason) {
// TODO Auto-generated method stub
}
@Override
public void onLoadingCancelled(String imageUri,
View view) {
// TODO Auto-generated method stub
}
});
// Image resize
public Bitmap resizedBitmap(Bitmap bm, int newHeight, int newWidth) {
int width = bm.getWidth();
int height = bm.getHeight();
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
// CREATE A MATRIX FOR THE MANIPULATION
Matrix matrix = new Matrix();
// RESIZE THE BIT MAP
matrix.postScale(scaleWidth, scaleHeight);
// RECREATE THE NEW BITMAP
Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false);
return resizedBitmap;
}
注意： 别忘了添加通用图像加载程序库。
答案 2 :(得分：0)
没有理由不工作。确保calculateInSampleSize正常运行。
options.inSampleSize需要高于1.确保您在此处获得有效值。
答案 3 :(得分：0)
尝试以下代码：
public void DownloadImageFromPath(String path){
InputStream in =null;
Bitmap bmp=null;
ImageView iv = (ImageView)findViewById(R.id.img1);
int responseCode = -1;
try{
URL url = new URL(path);//"http://192.xx.xx.xx/mypath/img1.jpg
HttpURLConnection con = (HttpURLConnection)url.openConnection();
con.setDoInput(true);
con.connect();
responseCode = con.getResponseCode();
if(responseCode == HttpURLConnection.HTTP_OK)
{
//download
in = con.getInputStream();
bmp = BitmapFactory.decodeStream(in);
in.close();
iv.setImageBitmap(bmp);
}
}
catch(Exception ex){
Log.e("Exception",ex.toString());
}
}
答案 4 :(得分：0)
只需在位图中获取下载的文件，然后在imageView中设置位图
URL url = new URL(urlString);
Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
imageView.setImageBitmap(bmp);
希望有所帮助