扩展ArrayAdapter并覆盖getView时，传递resource/textViewResourceId参数是否完全多余? [英] When extending an ArrayAdapter and overriding getView, is passing the resource/textViewResourceId arguments completely redundant?

问题描述

我一直在为ListViews定制自定义ArrayAdapters，在扩展它们时，我总是一直简单地将-1(不存在的资源ID)作为super的资源参数传递.当您还覆盖getView时，将其他任何内容传递给它是否有任何潜在的好处?

I've been messing around with custom ArrayAdapters for ListViews a bit, and when extending them I've always simply passed -1 (A non-existent resource id) as the resource argument to super. Are there any potential benefits (at all) to passing anything else in it's place when you also override getView?

推荐答案

当您还覆盖getView时，将其他任何内容传递给它是否有任何潜在的好处?

Are there any potential benefits (at all) to passing anything else in it's place when you also override getView?

好的.如果传递您的实际布局和TextView资源ID，则可以让super.getView()方法处理View膨胀并在单个TextView上分配文本.然后，您的getView()替代项仅需要填充空白".

Sure. If you pass your actual layout and TextView Resource ID, you can let the super.getView() method handle the View inflation and assigning the text on a single TextView. Then your getView() override would just need to "fill in the blanks".

例如，假设我们有以下简单的列表项类:

For example, say we have the following simple list item class:

public class Item {
    String text;
    int imageResId;

    public Item(String text, int imageResId) {
        this.text = text;
        this.imageResId = imageResId;
    }

    @Override
    public String toString() {
        return text;
    }
}

还有一个简单的项目布局，如下所示:

And a simple item layout like so:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical">

    <ImageView android:id="@+id/item_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView android:id="@+id/item_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

然后我们的ArrayAdapter子类可能就是这样:

Then our ArrayAdapter subclass could be simply this:

public class MyAdapter extends ArrayAdapter<Item> {
    public MyAdapter(Context context, List<Item> items) {
        super(context, R.layout.list_item, R.id.item_text, items);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = super.getView(position, convertView, parent);

        ((ImageView) v.findViewById(R.id.item_image))
            .setImageResource(getItem(position).imageResId);

        return v;
    }
}

请注意，我们在Item类中实现了toString()覆盖，以为ArrayAdapter提供正确的String.

Note that we implement a toString() override in our Item class to provide the correct String to ArrayAdapter.

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