Android適配器之定義PagerAdapter萬能適配器

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通常使用pageAdapter須要實現getcount、isViewFromObject、instantiateItem、destroyItem等默認函數，其實徹底能夠抽取共有代碼到父類當中。

/**
 * Created by Xiaoxuan948 on 2015/10/27.
 * Desc:
 * 提示：先給adapter設置數據，再綁定適配器    setAdapter會調用instantiateItem方法
 */
public class AbsUnityBasePageAdapter<T> extends PagerAdapter implements INotifyAdapterDataSetChange {
    private static final UtilsLog lg = UtilsLog.getLogger(AbsUnityBasePageAdapter.class.getSimpleName());
    private LayoutInflater layoutInflater;

    private IAdapterDataModifyHelper<T> IAdapterataModifyHelper;

    public AbsUnityBasePageAdapter() {
        this.IAdapterataModifyHelper = new DataModifyHelper<>();
    }

    public IAdapterDataModifyHelper<T> getDataModifyHelper() {
        this.IAdapterataModifyHelper.setNotifyAdapterDataSetChange(this);
        return IAdapterataModifyHelper;
    }

    @Override
    public void notifyAdapter() {
        lg.e("notifyAdapter with dataSize:" + this.IAdapterataModifyHelper.getDataResources().size());
        notifyDataSetChanged();
    }

    /*PagerAdapter默認必須實現方法*/
    @Override
    public boolean isViewFromObject(View view, Object object) {
        lg.e("isViewFromObject:" + (view == object ? "true" : "false"));
        return view == object;
    }


    @Override
    public int getCount() {
        return IAdapterataModifyHelper.getDataResources().size();
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        if (layoutInflater == null) {
            layoutInflater = LayoutInflater.from(container.getContext());
        }
        if (position >= IAdapterataModifyHelper.getDataResources().size()) {
            lg.e("修正position：instantiateItem failed for position:" + position + " out of size:" + IAdapterataModifyHelper.getDataResources().size());
            position = position % getDataModifyHelper().getDataResources().size();
        }

        lg.e("generateItemView for position:" + position);
        View itemView = generateItemView(IAdapterataModifyHelper.getDataResources().get(position), layoutInflater, position);
        container.addView(itemView);
        return itemView;
    }

    @Override
    //不調用會報錯
    public void destroyItem(ViewGroup container, int position, Object object) {
        lg.e("destroyItem:" + position);
        container.removeView((View) object);
    }

    /*自定義的抽象方法:基於Position構建View對象*/
    protected View generateItemView(T itemEntity, LayoutInflater layoutInflater, int position) {
        if (itemEntity instanceof View) {
            return (View) IAdapterataModifyHelper.getDataResources().get(position);
        } else {
            throw new NullPointerException("DataResource Type is not View,so child class must Override");
        }
    }
}

其中，IAdapterataModifyHelper當中封裝對數據的增刪改查等操做，而且已內部處理空指針異常。

instantiateItem中國，首先經過數組是否越界矯正position，調用generateItemView方法生成View對象並添加至container當中。在generateItemView實現當中，默認實現會判斷當前數據集是否爲View的集合，不然拋出異常，這裏主要是爲了強制開發人員重寫generateItemView根據itemEntity生成View對象。

業務層使用方式以下：

adapter = new AbsUnityBasePageAdapter<String>() {

    @Override
    protected View generateItemView(String itemEntity, LayoutInflater layoutInflater, int position) {
        lg.e("ViewPagerLabBaseAdapter generateItemView with position :" + position);
        View itemRootView = layoutInflater.inflate(R.layout.simple_item_vertical, null);
        ViewFindHelper viewFindHelper = new ViewFindHelper(itemRootView);
        ImageView imgItemCommon = viewFindHelper.generateView(R.id.imgItemCommon);
        imgItemCommon.setScaleType(ImageView.ScaleType.CENTER_CROP);
        Glide.with(layoutInflater.getContext()).load(itemEntity).into(imgItemCommon);
        return itemRootView;
    }
};

adapter.getDataModifyHelper().setDataResource(
        "http://tupian.enterdesk.com/2013/mxy/12/10/15/3.jpg",
        "http://pic1.nipic.com/2008-11-13/2008111384358912_2.jpg",
        "http://img4.imgtn.bdimg.com/it/u=1249974208,2325623016&fm=21&gp=0.jpg",
        "http://img0.imgtn.bdimg.com/it/u=1918423052,1540132432&fm=21&gp=0.jpg");
vpActViewPager.setAdapter(adapter);

源碼連接： https://github.com/xiaoxuan948/AndroidUnityLab/tree/master/unity_base_dev_helper/src/main/java/com/coca/unity_base_dev_helper/adapter

來自爲知筆記(Wiz)