Android Volley ImageListener onResponse 行为

Question

我正在使用 Android Volley Library，我的问题应该很容易回答，如果你知道 ;)。

我需要知道 com.android.volley.toolbox.ImageLoader.ImageListener 的确切行为处理成功的响应。文档说

The call flow is this: 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. 2. After a network response returns, only one of the following 
cases will happen: - onResponse(response, false) will be called if the 
image was loaded. or - onErrorResponse will be called if there was an error 
loading the image.

我想知道的是:这是否意味着我可以将 onResponse 调用两次(首先将 isImmediate 设置为 false 并然后设置为 true)？我可以依靠它吗？我的意思是它会一直这样吗(如果图片加载成功)？

我正在尝试做这样的事情

imageLoader.get(image.getUrl(), new ImageListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        callback.call(null, error);
                    }

                    @Override
                    public void onResponse(ImageContainer response,
                            boolean isImmediate) {
                        if (response.getBitmap() != null) {
                            callback.call(response.getBitmap(), null);
                        }
                    }
                });

我需要 callback.call() 在图像加载成功时被调用，我还需要 response.getBitmap() 返回实际位图而不是空。

提前致谢!

Answer 1

What I want to know is this: does that mean that I can have onResponse called twice (first with isImmediate set to false and then set to true)? Can I rely on that? I mean will it always be like this (if the image loading is succesful)?

简短回答:是。

除非更改此类的实现(而且我非常怀疑会发生这种情况)，否则您可以依赖此调用顺序。

如果有帮助，我在此处的另一个答案中详细介绍了三种可能的响应情况:https://stackoverflow.com/a/32464875/3227795