Android:在View类中使用getTag()和setTag() [英] Android:Purpose of getTag() and setTag() in View Class

问题描述

public void setTag(final Object tag) {
                mTag = tag;
}
public Object getTag() {
            return mTag;
}

这是Android中View类的两种方法. 以下分别是这两种方法的官方文档.

These are two methods from View Class in Android. Following is the official documentation of these two methods respectively.

 /**
     * Returns this view's tag.
     *
     * @return the Object stored in this view as a tag
     *
     * @see #setTag(Object)
     * @see #getTag(int)


        */
 /**
     * Sets the tag associated with this view. A tag can be used to mark
     * a view in its hierarchy and does not have to be unique within the
     * hierarchy. Tags can also be used to store data within a view without
     * resorting to another data structure.
     *
     * @param tag an Object to tag the view with
     *
     * @see #getTag()
     * @see #setTag(int, Object)
     */

标记函数在baseadapter实现中被广泛使用，但是我无法理解其目的以及如何使用它们.您能否解释这个很好的例子，以帮助我理解这些功能的作用

tag functions are used extensively in baseadapter implementation but I couldn't understand its purpose and how to use them. Can you please explain this some good example to help me understand the role of these functions

推荐答案

尽可能简单地考虑它-一个标签".

Think of it as as plainly simple as it's possible - a "tag".

杂货店产品标签会告诉您什么? 基本上有很多东西，例如名称，价格，原产国，折扣等等.

What does a grocery shop product tag tell you? Basically a lot of things, such as name, price, origin country, discount, and many others.

想象一下，您正在制作一个使用ImageView在网格中显示此类产品的应用程序. 如何从ImageView轻松确定产品功能?对其进行标记是可能的解决方案之一.

Imagine you're making an application that displays such products in a grid using ImageView's. How to easily determine the product features from the ImageView? Tagging it is one of the possible solutions.

class Product {

    String mName;
    String mManufacturer;
    String mOriginCountry;

    double mPrice;
    int mDiscount;

    int mImageId; // A reference to a drawable item id
}

[...]

class My Activity {

    @Override
    protected void onCreate() {
        [...] // Some code

        // Grab the imageView reference and grab (or create) the tag for it
        ImageView someItemView = (ImageView) findViewById(R.id.some_product_view);
        Product someProductTag = new Product( ... some data ...);

        // Add the tag to the ImageView
        someItemView.addTag(someProductTag);
    }

    private void displayItemInfo(ImageView iv) {

        // Grab the tag and display the info.
        String productName = ((Product)iv.getTag()).mName();
        Toast.show(mContext, "This is " + productName, Toast.LONG).show(); 

    }

}

当然，这是非常简化的.理想情况下，您将拥有一个适配器，该适配器可以根据提供的标签创建视图，或者自动创建标签.

Of course this is very simplified. Ideally you would have an adapter which would create the view basing on your provided tags, or would create your tags automatically.

希望您能理解

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