凌空，ImageLoader.ImageListener中的onResponse调用了多少次 [英] Volley, How many times the onResponse in ImageLoader.ImageListener called

问题描述

我使用Volley进行互联网请求.我认为onResponse方法在收到响应时应该只调用一次，但是我发现它被调用了两次.

I‘ using Volley to do internet requests. I think the onResponse method should be called only once when receive a response, but I found it called twice.

这是我的代码:

YVolley.getInstance(context).getImageLoader().get(category.child.get(i).icon, new ImageLoader.ImageListener() {
                @Override
                public void onResponse(ImageLoader.ImageContainer response, boolean isImmediate) {
                    Drawable drawable = new BitmapDrawable(context.getResources(), response.getBitmap());
                    drawable.setBounds(0, 0, GeneralUtil.dip2px(context, 45), GeneralUtil.dip2px(context, 45));
                    button.setCompoundDrawables(null, drawable, null, null);
                    Log.i("swifter", "get icon ... success == "+url);
                }

                @Override
                public void onErrorResponse(VolleyError error) {
                    Log.i("swifter", "get drawable icon error...");
                }
            });

成功"日志打印了两次.

The "success" Log printed twice.

我的代码有问题吗?还是应该像这样?

Is there something wrong with my code or it should be like this ?

推荐答案

我在

I found the answer to this in the documentation for ImageLoader.java. The documentation states:

呼叫流程是这样:

The call flow is this:

1. 在附加到请求后，将调用onResponse(response, true)以反映所有已可用的缓存数据.如果数据可用，则response.getBitmap()将为非空.

1. Upon being attached to a request, onResponse(response, true) will be invoked to reflect any cached data that was already available. If the data was available, response.getBitmap() will be non-null.

网络响应返回后，只会发生以下情况之一:

After a network response returns, only one of the following cases will happen:

如果图像已加载，将调用
• onResponse(response, false)或
如果加载图像时出错，将调用
• onErrorResponse.

• onResponse(response, false) will be called if the image was loaded, or
• onErrorResponse will be called if there was an error loading the image.

基于此，可能的响应共有三种模式.我已经在示例应用程序中测试并确认了这些.

Based on this there are three patterns of possible responses. I have tested and confirmed these in a sample application.

在这种情况下，会有一个呼叫:

In this case there will be one call:

• onRespsonse(response, true)将被调用，您可以从response.getBitmap()获取图像.

• onRespsonse(response, true) will be called, and you can get the image from response.getBitmap().

在这种情况下，将有两个呼叫:

In this case there will be two calls:

• 首先，将调用onRespsonse(response, true)，而response.getBitmap()将是null.

然后，将调用onRespsonse(response, false)，您可以从response.getBitmap()获取图像.

Then, onRespsonse(response, false) will be called, and you can get the image from response.getBitmap().

在这种情况下，将有两个呼叫:

In this case there will be two calls:

• 首先，将调用onRespsonse(response, true)，而response.getBitmap()将是null.

然后，将调用onErrorResponse(error)，并且可以从error(这是VolleyError的实例)中找到错误的详细信息.

Then, onErrorResponse(error) will be called, and details of the error can be found from error (which will be an instance of VolleyError).

对于您而言，以下代码段将帮助您跳过第一个空"响应:

In your case, the following code snippet will help you to skip the first "empty" response:

@Override
public void onResponse(ImageLoader.ImageContainer response, boolean isImmediate) {
    // skip cache failure
    if (isImmediate && response.getBitmap() == null) return;

    // ...
}

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希望这有助于弄清为什么您可能会收到两个针对您请求的回复.

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Hopefully this helps to clear up why you may be getting two responses to your request.

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