快速開發Adapter

1、首先將getView以外的方法重寫，簡化重複步驟：

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.widget.BaseAdapter;

public abstract class DefaultAdapter<T> extends BaseAdapter {
	private final List<T> mList;
	private Context mContext;
	private LayoutInflater inflater;

	public DefaultAdapter(Context context, List<T> list) {
		mContext = context;
		mList = list;
		inflater = LayoutInflater.from(mContext);
	}
	
	public Context getContext() {
		return mContext;
	}
	
	public LayoutInflater getInflater() {
		return inflater;
	}
	
	public List<T> getList() {
		return mList;
	}

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

	@Override
	public Object getItem(int position) {
		return mList.get(position);
	}

	@Override
	public long getItemId(int position) {
		return position;
	}
}

這樣自己的adapter只要重寫getView方法就可以。

2、一般情況下adapter都只有一個佈局文件，不會重寫getViewTypeCount方法，這是可以進一步簡化：

import java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;

public abstract class DefaultSingleAdapter<T> extends DefaultAdapter<T> {
	private int mResourceId;
	
	public abstract Object onCreateViewHolder(View convertView);
	public abstract void onBindViewHolder(Object viewHolder, int position);
	
	public DefaultSingleAdapter(Context context, int resourceId, List<T> list) {
		super(context, list);
		mResourceId = resourceId;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		Object viewHolder = null;
		if(convertView == null) {
			convertView = getInflater().inflate(mResourceId, parent, false);
			viewHolder = onCreateViewHolder(convertView);
			convertView.setTag(viewHolder);
		} else {
			viewHolder = convertView.getTag();
		}
		onBindViewHolder(viewHolder, position);
		return convertView;
	}
}

這樣自己的adapter只要重寫兩個方法就可以，如下：

public class CityAdapter extends DefaultSingleAdapter<City> {

	public CityAdapter(Context context, List<City> list) {
		super(context, R.layout.layout_city_item, list);
	}

	private static final class ViewHolder {
		TextView tv_id;
		TextView tv_name;
		
		public ViewHolder(View view) {
			tv_id = (TextView) view.findViewById(R.id.tv_id);
			tv_name = (TextView) view.findViewById(R.id.tv_name);
		}
	}
	
	@Override
	public Object onCreateViewHolder(View convertView) {
		return new ViewHolder(convertView);
	}

	@Override
	public void onBindViewHolder(Object viewHolder, int position) {
		ViewHolder holder = (ViewHolder) viewHolder;
		City city = (City) getItem(position);
		holder.tv_id.setText(String.valueOf(city.getId()));
		holder.tv_name.setText(city.getName());
	}
}

和以前相比簡化了大部分的重複代碼，哈哈！

========2015-3-9==========

其實viewholder也可以用泛型來代替的，這樣回調中就不用強轉了：

public abstract class DefaultSingleAdapter<T, K> extends DefaultAdapter<T> {
	private int mResourceId;
	
	public abstract K onCreateViewHolder(View convertView);
	public abstract void onBindViewHolder(K viewHolder, int position);
	
	public DefaultSingleAdapter(Context context, int resourceId, List<T> list) {
		super(context, list);
		mResourceId = resourceId;
	}

	@SuppressWarnings("unchecked")
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		K viewHolder = null;
		if(convertView == null) {
			convertView = getInflater().inflate(mResourceId, parent, false);
			viewHolder = onCreateViewHolder(convertView);
			convertView.setTag(viewHolder);
		} else {
			viewHolder = (K) convertView.getTag();
		}
		onBindViewHolder(viewHolder, position);
		return convertView;
	}
}