Android ListView 多种布局--进阶二

Android ListView 多种布局–进阶一 中提及了这么一个需求，本博文就这个需求的实现做进一步探讨。

前面是单列，后面是双列的情况，使用ListView实现，一般的解决思路是处理getView和getCount方法，如下实现：

• 首先实现Adapter，处理getView和getCount方法

public class DoubleAdapter extends BaseAdapter implements OnClickListener{
    private List<String> mDataList = new ArrayList<String>();
    private Context mContext;

    private final static int PRESIZE = 5;

    public DoubleAdapter(Context context,List<String> datas){
        this.mContext = context;
        this.mDataList = datas;
    }
    @Override
    public int getCount() {
        return PRESIZE + (mDataList.size()- PRESIZE) % 2 == 0 ? (mDataList.size()- PRESIZE) / 2 : (mDataList.size()- PRESIZE) / 2 + 1;
    }
    @Override
    public Object getItem(int position) {
        return null;
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @SuppressLint("InflateParams")
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHodler hodler = null;
        if(convertView == null){
            hodler = new ViewHodler();
            LayoutInflater inflater = LayoutInflater.from(mContext);
            convertView = inflater.inflate(R.layout.item, null);
            hodler.textView1 = (TextView) convertView.findViewById(R.id.text1);
            hodler.textView2 = (TextView) convertView.findViewById(R.id.text2);
            hodler.layout1 = (LinearLayout) convertView.findViewById(R.id.item_layout1);
            hodler.layout2 = (LinearLayout) convertView.findViewById(R.id.item_layout2);

            convertView.setTag(hodler);
        }else{
            hodler = (ViewHodler) convertView.getTag();
        }

        if (position >= PRESIZE ) {

            String item1 = "";
            String item2 = "";

            if(position * 2 + 1< mDataList.size()){
                item1 = mDataList.get(position * 2 - PRESIZE);
                item2 = mDataList.get(position * 2 + 1 - PRESIZE);
            }else if(position * 2 + 1== mDataList.size()){
                item1 = mDataList.get(position * 2 - PRESIZE);
                item2 = "";
            }

            if(item1 != null){
                hodler.textView1.setText(item1);
                hodler.layout1.setOnClickListener(this);
                hodler.layout1.setTag(item1);
            }

            if(item2 != null){
                hodler.textView2.setText(item2);
                hodler.layout2.setOnClickListener(this);
                hodler.layout2.setTag(item2);
            }
        }else {
            String item = mDataList.get(position);
            hodler.textView1.setText(item);
            hodler.layout1.setOnClickListener(this);
            hodler.layout1.setTag(item);

            hodler.textView2.setText("");
            hodler.layout2.setOnClickListener(this);
            hodler.layout2.setTag("");
        }



        return convertView;
    }

    class ViewHodler {
        TextView textView1;
        TextView textView2;
        LinearLayout layout1;
        LinearLayout layout2;
    }
    @Override
    public void onClick(View v) {
        Toast.makeText(mContext, v.getTag().toString(), Toast.LENGTH_SHORT).show();
    }
}

• 接着是Activity将数据绑定View

public class DoubleListViewActivity extends Activity {
    private List<String> datas;
    private ListView listView;
    private DoubleAdapter adapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        getData();
        initView();
    }

    private void initView(){
        listView = (ListView) findViewById(R.id.listView);
        adapter = new DoubleAdapter(this, datas);
        listView.setAdapter(adapter);
    }

    private void getData(){
        datas = new ArrayList<String>();
        for(int i = 0;i < 60;i++){
            datas.add("NO:"+i);
        }
    }
}

我们来看看关键的实现点：

@Override
public int getCount() {
    return PRESIZE + (mDataList.size()- PRESIZE) % 2 == 0 ? (mDataList.size()- PRESIZE) / 2 : (mDataList.size()- PRESIZE) / 2 + 1;
}

@SuppressLint("InflateParams")
@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHodler hodler = null;

    if(position * 2 + 1< mDataList.size()){
        item1 = mDataList.get(position * 2 - PRESIZE);
        item2 = mDataList.get(position * 2 + 1 - PRESIZE);
    }else if(position * 2 + 1== mDataList.size()){
        item1 = mDataList.get(position * 2 - PRESIZE);
        item2 = "";
    }
}

小结一下上面的实现思路: 主要是重新计算getCount，不满足偶数的补充一个， 重新绑定数据，每行绑定两个数据，然后一个Holder初始化对应的itemView，再更新到view上去。

上面的实现思路只能说很一般，比较麻烦的是计算getCount和getView的处理，有木有更好的方式处理一行两列的ListView思路呢？

当然有的，其实很简单，就是从数据端入手，而不是像上面那样从绑定到View处着手，那么从数据端该如何着手呢，其实就是将原有的数据封装一下，每两个bean封装成一个bean，接下来绑定过程和普通的Adapter一样，这样说是不是问题就迎刃而解了，简单看一下实现吧

• 首先将数据封装一下

public static final class BrandRecommedProduct {
    private ProductBean productLeft;
    private ProductBean productRight;
    public BrandRecommedProduct() {
    }
    public BrandRecommedProduct(ProductBean productLeft, ProductBean productRight) {
        this.productLeft = productLeft;
        this.productRight = productRight;
    }
    public ProductBean getProductLeft() {
        return productLeft;
    }
    public void setProductLeft(ProductBean productLeft) {
        this.productLeft = productLeft;
    }
    public ProductBean getProductRight() {
        return productRight;
    }
    public void setProductRight(ProductBean productRight) {
        this.productRight = productRight;
    }
}

• 接着初始化List数据（将奇数数据去掉最后一个保持始终偶数个数据）

private void updateRecommendProducts(List<ProductBean> recommendProducts) {
    int size = 0;
    if (recommendProducts != null && (size = recommendProducts.size()) > 0) {
        mDataList.add(BrandDetailAdapter.RECOMMEND_PRODUCT_TITLE);
        mRecommendProductSize = size % 2 == 0 ? size : size -1;

        for (int i = 0; i < size; i++) {
            if (size % 2 == 0) {
                BrandRecommedProduct product = new BrandRecommedProduct();
                product.setProductLeft(recommendProducts.get(i));
                i++;
                product.setProductRight(recommendProducts.get(i));
                mDataList.add(product);
            }else {
                if (i == size -1 ) {
                    break;
                }

                BrandRecommedProduct product = new BrandRecommedProduct();
                product.setProductLeft(recommendProducts.get(i));
                i++;
                product.setProductRight(recommendProducts.get(i));
                mDataList.add(product);
            }
        }

        if(mBrandDetailBean.getCat() != null){
            mDataList.add(mBrandDetailBean.getCat());
        }

        mAdapter.notifyDataChanged(mDataList);
    }
} 

这样就可以在初始化数据的时候就包装了两个对等的数据，这样在通过Adapter绑定View的时候就和普通ListView处理相同了。这么做对于简单的View体现不出来很大的优势，如果是复杂的ListView布局就很能体现优势了.