Android studio 最常用的控件ListView
ListView 可以算是最常用的控件之一了，由于屏幕控件有限，当我们有大量的数据需要展示的时候，就要借助ListView来实现，通过屏幕滚动的方式来展示数据
我们先建立一个ListViewTest项目，然后修改activity_main.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"
>
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
接着修改MainActivity中的代码
package com.example.listview;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private String[] data = {"apple","bannner","orange","watermelon","pear","grape",
"pineapple","strawberry","cherry","mango","apple","bannner","orange",
"watermelon","pear","grape", "pineapple","strawberry","cherry","mango"
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
MainActivity.this,android.R.layout.simple_list_item_1,data);
ListView listView = findViewById(R.id.list_view);
listView.setAdapter(adapter);//把构造好的适配器对象传进去
}
这里我们简单的设置一个data数组作为数据源，数组中的数据是无法直接传递给ListView的，我们需要借助适配器来完成，我觉得Android中最好用的就是ArrayAdapter，可以通过泛型来指定要适配的数据类型，在构造函数中把数据传入，android.R.layout.simple_list_item_1是一个内置的布局文件，一个最简单的ListView就做好了
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很多时候我们实际应用中都不能只是一段文本，还有图片，接下来我们来给ListView加上图片和点击事件
首先定义一个实体类，作为ListView适配器的适配类型，新建类Fruit
package com.example.listview;
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;
}
}
然后为ListView指定一个自定义的布局，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="wrap_content">
<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>
然后自定义一个适配器，新建类FruitAdapter
package com.example.listview;
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;
//重写构造函数，把id和数据传进来
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 = LayoutInflater.from
(getContext()).inflate(resourceId, parent, false);
*/
//对上一个语句进行优化
View view;
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);//false参数表示只让我们在父布局中声明的layout属性生效
}else {
view = convertView;
}
ImageView fruitImage = view.findViewById(R.id.fruit_image);
TextView fruitName = view.findViewById(R.id.fruit_name);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
}
}
最后修改MainActivity
package com.example.listview;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<>();
/*private String[] data = {"apple","bannner","orange","watermelon","pear","grape",
"pineapple","strawberry","cherry","mango","apple","bannner","orange",
"watermelon","pear","grape", "pineapple","strawberry","cherry","mango"
};*/
@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);
//ArrayAdapter<String> adapter = new ArrayAdapter<String>(
// MainActivity.this,android.R.layout.simple_list_item_1,data);
ListView listView = findViewById(R.id.list_view);
listView.setAdapter(adapter);
//注册监听器
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_LONG).show();
}
});
}
private void initFruits() {
for(int i = 0;i<2;i++){//循环两遍，只添加一遍的话不足以充满屏幕
Fruit apple = new Fruit("apple",R.drawable.ic_launcher_background);//这里懒得找图片了，直接用系统图片
fruitList.add(apple);
Fruit banana = new Fruit("banana",R.drawable.ic_launcher_background);
fruitList.add(banana);
Fruit orange = new Fruit("orange",R.drawable.ic_launcher_background);
fruitList.add(orange);
Fruit watermelon = new Fruit("watermelon",R.drawable.ic_launcher_background);
fruitList.add(watermelon);
Fruit pear = new Fruit("pear",R.drawable.ic_launcher_background);
fruitList.add(pear);
Fruit grape = new Fruit("grape",R.drawable.ic_launcher_background);
fruitList.add(grape);
Fruit pineapple = new Fruit("pineapple",R.drawable.ic_launcher_background);
fruitList.add(pineapple);
Fruit cherry = new Fruit("cherry",R.drawable.ic_launcher_background);
fruitList.add(cherry);
Fruit mango = new Fruit("mango",R.drawable.ic_launcher_background);
fruitList.add(mango);
}
}
}
- 最后我们来运行一下效果
