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
-
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> -
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> -
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）
-
拿到一个水果
Fruit fruit = getItem(position); -
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) -
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
-
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> -
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> -
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。