java - 一个适配器多种数据类型 - android

Question

我的应用程序需要能够更改 GridView 中显示的可绘制对象，主要是颜色和显示的一些信息。不同的样式有不同的.java和XML文件。

不同的 .java 文件用于显示同一事物的不同类型，因此从共享父级继承，例如 basicrunner 扩展 runner 和 lollipoprunner 扩展 runner。

适配器扩展了BaseAdapter，并重写了getItem等方法，但它们指定了一种返回类型；

public class RunnersAdapter extends BaseAdapter {
private static final String TAG = "RunnersAdapter";

//used in switch statement to decide which XML to inflate
private static final int LayoutTYPE_1 = 1;  
private static final int LayoutTYPE_2 = 2;
private static final int LayoutTYPE_3 = 3;
int layout = 2; //hard coded just for testing

@Override
public Runner getItem(int position) { //runner is superclass
    return mRunners.get(mKeys[position]);
}

有没有办法为每种类型的运行者使用这个 RunnersAdapter，还是我最好为每种类型制作不同的适配器？

编辑:

这是对仅需要显示一种数据类型(即 Runner)的适配器的升级。现在我们想要显示多种不同类型的运行者，但不一定要制作多种类型的适配器。

更多代码来说明我的意思:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) mContext
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

if(layout == LayoutTYPE_1){ //LollipopView

            Runner runner = getItem(position); //should be a lollipopRunner!!

            gridView = inflater.inflate(R.layout.lollipopRunner, null); //use lollipopRunner XML
}else if(layout == LayoutTYPE_2){

            Runner runner = getItem(position);  //should be basicRunner!!

            gridView = inflater.inflate(R.layout.basicrunner, null); //use basic runner XML

如上所示，重写的 getItem 方法返回类型“Runner”，它是 BasicRunner 和 LollipopRunner 的父类。

是否有正确的多态性应用可以使其发挥作用？每个运行者都需要新的适配器吗？

Answer 1

BaseAdapter 有几个可以重写的方法，以便根据位置返回不同类型的 View 。

这些是:

        @Override
        public int getItemViewType(int position) {
            if (...) return 1;
            else if (...) return 2;
            else if (...) return 3;
            else return 4;
        }

        @Override
        public int getViewTypeCount() {
            return 4; //total number of different type of views 
        }


        @Override
        public View getView(int position, View view, ViewGroup viewGroup) {


            switch (getItemViewType(position)) {
                case 0:
                    if (view == null) {
                        view = mActivity.getLayoutInflater().inflate(R.layout.message_item_1, viewGroup, false);
                    }
                    break;
                case 1:
                    if (view == null) {
                        view = mActivity.getLayoutInflater().inflate(R.layout.message_item_1_media, viewGroup, false);
                    }
                    break;
                case 2:
                    if (view == null) {
                        view = mActivity.getLayoutInflater().inflate(R.layout.message_item_2, viewGroup, false);
                    }
                    break;
                case 3:
                    if (view == null) {
                        view = mActivity.getLayoutInflater().inflate(R.layout.message_item_2_media, viewGroup, false);
                    }
                    break;
            }
    }

编辑:

将数据提供给适配器时，您可以将其作为对象列表传递，稍后您可以根据您的类型进行向下转换。

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) mContext
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

if(layout == LayoutTYPE_1){ //LollipopView

            // getItem(postion) will give you Object - downcast it as per the position.

            Runner runner = (LollipopRunner)(getItem(position)); //downcast to lollipopRunner

            gridView = inflater.inflate(R.layout.lollipopRunner, null); //use lollipopRunner XML
}else if(layout == LayoutTYPE_2){

            Runner runner = (BasicRunner)(getItem(position));  //downcasted to basic runner

        gridView = inflater.inflate(R.layout.basicrunner, null); //use basic runner XML