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[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。


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。

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