1.最简单的ListView(只填充数据,不做样式修改)
1.1在布局中添加ListView控件
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ListView
android:id="@+id/lv"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</android.support.constraint.ConstraintLayout>
只需要指定id,宽高建议指定为占满,可根据需求改动。
1.2在MainActivity中修改代码
public class MainActivity extends AppCompatActivity {
private String [] data = {"one","two","three","four"};
private ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
listView = findViewById(R.id.lv);
listView.setAdapter(arrayAdapter);
}
}
先建一个String数组data放数据,数据自定义,然后借助适配器将数据输入ListView中,利用ArrayAdapter,通过泛型指定数据类型,这里是String。ArrayAdatper构造函数中有三个参数,分别是上下文(当前的activity)、list view的条目的样式(这里是用的系统自带的布局,里面只有一个text view)、需要填入的数据。最后传入list view的布局,将适配器与list view关联就可以使用了。
1.3效果图
2.自定义界面
自定义界面主要是建一个Adapter,在其中添加自己想要的东西,再将adapter与list view关联使用
实现的样式:
如图,每个item是一张图片和文字。
2.1为了使文字和图片能对应,建一个类用于适配数据。新建Fruit类:
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;
}
}
建一个item的布局(listview_item.xml),用于自定义我们想显示的item的样式,这里item中只需要一个text view和一个image view
<?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"
android:orientation="horizontal">
<ImageView
android:id="@+id/fruit_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:maxWidth="40dp"/>
<TextView
android:id="@+id/fruit_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:layout_marginStart="10dp"/>
</LinearLayout>
2.2建立一个适配器,这个适配器继承自ArrayAdapter,其中泛型指定为Fruit类
package com.example.listviewtest;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
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(@NonNull Context context, int textViewResourceId, @NonNull List<Fruit> objects) {
super(context,textViewResourceId, objects);
resourceId = textViewResourceId;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
Fruit fruit = getItem(position);//得到当前item的index
//不进行性能优化,每次调用getView()都会加载一遍布局,当快速滑动时,可能会卡出白屏
// View view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
// ImageView imageView = view.findViewById(R.id.fruit_image);
// TextView textView = view.findViewById(R.id.fruit_name);
// imageView.setImageResource(fruit.getImageId());
// textView.setText(fruit.getName());
View view;
ViewHolder viewHolder;//缓存控件实例,不用每次都加载
if (convertView == null){//convertView:将之前加载好的布局进行缓存
view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
//利用viewHolder
viewHolder = new ViewHolder();
//绑定自定义的item布局中的控件
viewHolder.fruitImage = view.findViewById(R.id.fruit_image);
viewHolder.fruitName = view.findViewById(R.id.fruit_name);
//将view holder存储在view中
view.setTag(viewHolder);
}else {
view = convertView;
viewHolder = (ViewHolder) view.getTag();//强转,重新获取view holder
}
//放入数据和图片,缓存
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
private class ViewHolder {
ImageView fruitImage;
TextView fruitName;
}
}
2.3MainActivity中
package com.example.listviewtest;
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 = {"one","two","three","four"};
private ListView listView;
private List<Fruit> list = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruit();
//item布局改成自己自定义的布局,数据改成泛型指定为Fruit的list
FruitAdapter fruitAdapter = new FruitAdapter(MainActivity.this,R.layout.listview_item,list);
// ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
listView = findViewById(R.id.lv);
listView.setAdapter(fruitAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Fruit fruit = list.get(position);
Toast.makeText(MainActivity.this,fruit.getName(),Toast.LENGTH_SHORT).show();
}
});
}
private void initFruit() {
for (int i = 0; i <10; i++) {
Fruit one = new Fruit("apple0",R.mipmap.green);
list.add(one);
Fruit two = new Fruit("apple1",R.mipmap.purple);
list.add(two);
}
}
}