标签：复习 fruit Fruit new Android ListView fruitList view
目录
一、ListView用法
1.新建项目
2.修改activity——main.xml代码
3.修改MainActivity.java代码
二、定制ListView界面
在上面的基础上
4.定义一个实体类Fruit.java，为ListView适配器的适配类型。
5.为ListView的子项指定一个我们自定义的布局。在layout目录下新建fruit_item.xml
6.自定义适配器，继承自ArrayAdapter,并将泛型指定为Fruit类，名为FruitAdapter
7.修改修改MainActivity.java代码，添加intiFruits()方法，来初始化所有水果数据。
一、ListView用法
1.新建项目
2.修改activity——main.xml代码
<?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">
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
</LinearLayout>
3.修改MainActivity.java代码
二、定制ListView界面
在上面的基础上
4.定义一个实体类Fruit.java，为ListView适配器的适配类型。
package com.example.listviewtest;
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
5.为ListView的子项指定一个我们自定义的布局。在layout目录下新建fruit_item.xml
<?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">
<ImageView
android:id="@+id/fruit_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"></ImageView>
<TextView
android:id="@+id/fruit_name"
android:gravity="center_vertical"
android:layout_marginLeft="10dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"></TextView>
</LinearLayout>6.自定义适配器，继承自ArrayAdapter,并将泛型指定为Fruit类，名为FruitAdapter
public class FruitAdapter extends ArrayAdapter<Fruit> {
private int resourceId;
public FruitAdapter(@NonNull Context context, int textViewResourceId, @NonNull List<Fruit> objects) {
super(context, textViewResourceId, objects);
resourceId = textViewResourceId;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
View view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
ImageView fruitImage = (ImageView)view.findViewById(R.id.fruit_image);
TextView fruitName = view.findViewById(R.id.fruit_name);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
} 7.修改修改MainActivity.java代码，添加intiFruits()方法，来初始化所有水果数据。
public class MainActivity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<Fruit>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruits();//初始化
FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);
ListView listView = (ListView)findViewById(R.id.list_view);
listView.setAdapter(adapter);
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
}
三、提升ListView的运行效率
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
View view;
if(convertView == null){
LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
}else{
view = convertView;
}
ImageView fruitImage = (ImageView)view.findViewById(R.id.fruit_image);
TextView fruitName = view.findViewById(R.id.fruit_name);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
}进一步优化
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
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 = view.findViewById(R.id.fruit_name);
view.setTag(viewHolder);
}else{
view = convertView;
viewHolder = (ViewHolder)view.getTag();
}
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
}四、设置ListView点击事件
public class MainActivity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<Fruit>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruits(); // 初始化水果数据
FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);
ListView listView = (ListView) findViewById(R.id.list_view);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Fruit fruit = fruitList.get(position);
Toast.makeText(MainActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
}
标签：复习,fruit,Fruit,new,Android,ListView,fruitList,view 来源： https://blog.csdn.net/weixin_44948004/article/details/122291390
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