[安卓]ListView 与 RecyclerView的比较

ListView与RecyclerView在在app应用非常广泛，相对于其他的view（button textview）来说比较复杂，接下来我将讲一下创建的流程以及两者的不同。

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代码来自《第一行代码》

秋天到了，果园大丰收了，现在着急的事情，就是把水果收集好放进仓库里。

ListView

1. 首先肯定要先把仓库准备好,腾一块地方出来，在布局中添加ListView。

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
   
        <ListView
            android:id="@+id/list_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </ListView>
   
    </LinearLayout>
   

2. 把装水果的框子准备好，创建fruit_item布局。

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
   
        <ImageView
            android:id="@+id/fruit_image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
   
        <TextView
            android:id="@+id/fruit_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:layout_marginLeft="10dp" />
   
    </LinearLayout>
   

3. 主角登场啦，咱们的搬运工，创建类FruitAdapter。

他需要干什么呢？

先贴出源码，下面解释

    package com.example.listviewtest;

    import android.content.Context;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.ImageView;
    import android.widget.TextView;

    import java.util.List;

    public class FruitAdapter extends ArrayAdapter<Fruit> {

        private int resourceId;

        public FruitAdapter(Context context, int textViewResourceId,
                            List<Fruit> objects) {
            super(context, textViewResourceId, objects);
            resourceId = textViewResourceId;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            Fruit fruit = getItem(position); // 获取当前项的Fruit实例
            View view;
            ViewHolder viewHolder;
            if (convertView == null) {
                view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
                viewHolder = new ViewHolder();
                viewHolder.fruitImage = (ImageView) view.findViewById (R.id.fruit_image);
                viewHolder.fruitName = (TextView) view.findViewById (R.id.fruit_name);
                view.setTag(viewHolder); // 将ViewHolder存储在View中
            } else {
                view = convertView;
                viewHolder = (ViewHolder) view.getTag(); // 重新获取ViewHolder
            }
            viewHolder.fruitImage.setImageResource(fruit.getImageId());
            viewHolder.fruitName.setText(fruit.getName());
            return view;
        }

        class ViewHolder {

            ImageView fruitImage;

            TextView fruitName;

        }

    }

搬运工的工作就是，返回一个装满水果的框框

• 拿到一个水果

• 找到一个框框

• 把水果放到框框里

• 把框框返回（结局自然回到里仓库）

  1. 拿到一个水果

      Fruit fruit = getItem(position);
     

  2. 找到一个框框

      View view;
      view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
      ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image)
      TextView fruitName = (TextView) view.findViewById(R.id.fruit_name)
     

  3. 把水果放到框框里

      viewHolder.fruitImage.setImageResource(fruit.getImageId());
      viewHolder.fruitName.setText(fruit.getName());
     

     源码里面有两布优化，自己想想哦。

  4.把框框返回

        return view;
  

RecylerView

还是老步骤，首先准备好仓库，在准备好框框

1. 准备好仓库，腾一块地方出来

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
   
        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
   
    </LinearLayout>
   

2. 准备好框框，和上面一样

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp" >
   
        <ImageView
            android:id="@+id/fruit_image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal" />
   
        <TextView
            android:id="@+id/fruit_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="left"
            android:layout_marginTop="10dp" />
   
    </LinearLayout>
   

3. 请出我们更加聪明的搬运工了

先贴出源码，下面解释

package com.example.recyclerviewtest;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder>{

    private List<Fruit> mFruitList;

    static class ViewHolder extends RecyclerView.ViewHolder {
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;

        public ViewHolder(View view) {
            super(view);
            fruitView = view;
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }

    public FruitAdapter(List<Fruit> fruitList) {
        mFruitList = fruitList;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);
        final ViewHolder holder = new ViewHolder(view);
        holder.fruitView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(v.getContext(), "you clicked view " + fruit.getName(), Toast.LENGTH_SHORT).show();
            }
        });
        holder.fruitImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(v.getContext(), "you clicked image " + fruit.getName(), Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }

    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

多了好多诶，其实，咱们聪明的搬运工制造了更多的工具，真是方便了好多。

现在搬运工只需要干两件事情了

• 找到一个水果

• 把水果放到框子里

    public void onBindViewHolder(ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
  

  没错，只需要两部，其他的事情都靠聪明的搬运工制造出来的自动小车，送回到仓库了，是不是很酷。

• 现在创造出我们的工具

    static class ViewHolder extends RecyclerView.ViewHolder {
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
  
        public ViewHolder(View view) {
            super(view);
            fruitView = view;
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }
  

  这个工具记得他应该去仓库中腾出来的位置

• 再看看工具是怎么运作的

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }
  

  首先他会和仓库联系一下，然后就会自动运回仓库啦。