本次的案例实现如下的水果列表:当下拉列表的时候,出现正在加载数据,然后并显示下一组数据。点击对应的购物车图标,则会显示XXX已加入购物车!
实现代码如下:
FruitItim.java
package cn.edu.hznu.ex5_0.bean;
public class FruitItem {
private int fruitImageId;
private String fruitName;
private double fruitPrice;
private int carImageId;
public FruitItem() {
}
public FruitItem(int fruitImageId, String fruitName, double fruitPrice, int carImageId) {
this.fruitImageId = fruitImageId;
this.fruitName = fruitName;
this.fruitPrice = fruitPrice;
this.carImageId = carImageId;
}
public int getFruitImageId() {
return fruitImageId;
}
public void setFruitImageId(int fruitImageId) {
this.fruitImageId = fruitImageId;
}
public String getFruitName() {
return fruitName;
}
public void setFruitName(String fruitName) {
this.fruitName = fruitName;
}
public double getFruitPrice() {
return fruitPrice;
}
public void setFruitPrice(double fruitPrice) {
this.fruitPrice = fruitPrice;
}
public int getCarImageId() {
return carImageId;
}
public void setCarImageId(int carImageId) {
this.carImageId = carImageId;
}
}
FruitResource.java
package cn.edu.hznu.ex5_0.bean;
import cn.edu.hznu.ex5_0.R;
/**
* Created by b on 2019/3/17.
*/
public class FruitResource {
public static int[] fruitImageIds={R.drawable.apple_pic, R.drawable.banana_pic,
R.drawable.cherry_pic,R.drawable.grape_pic,R.drawable.mango_pic, R.drawable.orange_pic,
R.drawable.pear_pic, R.drawable.pineapple_pic,R.drawable.strawberry_pic,R.drawable.watermelon_pic
};
public static String[] friutNames={"apple","banana","cherry","grape","mango",
"orange","pear","pineapple","strawberry","watermelon"};
}
FruitAdapter.java
package cn.edu.hznu.ex5_0.adapter;
import android.content.Context;
import android.support.annotation.NonNull;
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 android.widget.Toast;
import java.util.List;
import cn.edu.hznu.ex5_0.R;
import cn.edu.hznu.ex5_0.bean.FruitItem;
public class FruitAdapter extends ArrayAdapter <FruitItem> {
//列表项布局的id
private int item_layout_id;
public FruitAdapter(Context context, int resource, List objects) {
super(context, resource,objects);
item_layout_id=resource;
}
/**
* getView()方法:在加载每一个的时候被调用
* position:当次需要加载(显示)列表项的位置
* convertView:回收站,重复利用的子视图
* @param position
* @param convertView
* @param parent
* @return 返回的是加载的这个列表项的子视图
*/
@NonNull
@Override
public View getView(int position, View convertView, final ViewGroup parent) {
View view=null; //当前列表项的子视图
ViewHolder holder;
if(convertView==null){//回收站为空\
/**
* LayoutInflater.from()得到布局填充器对象
* getContext()获取当前上下文
* inflate() 加载填充布局
*/
view= LayoutInflater.from(getContext())
.inflate(item_layout_id,parent,false);
holder=new ViewHolder(view);
view.setTag(holder);
}else {//显示后续的列表项
view=convertView;
holder= (ViewHolder) view.getTag();
}
final FruitItem itemData=getItem(position);
holder.fruitImage.setImageResource(itemData.getFruitImageId());
holder.fruitName.setText(itemData.getFruitName());
holder.fruitPrice.setText(itemData.getFruitPrice()+"元/kg");
holder.carImage.setImageResource(itemData.getCarImageId());
holder.carImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(parent.getContext(),itemData.getFruitName()+ "已加入购物车!", Toast.LENGTH_SHORT).show();
}
});
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
TextView fruitPrice;
ImageView carImage;
public ViewHolder(View view){
fruitImage= (ImageView) view.findViewById(R.id.fruitImage);
fruitName= (TextView) view.findViewById(R.id.fruitName);
fruitPrice= (TextView) view.findViewById(R.id.fruitPrice);
carImage= (ImageView) view.findViewById(R.id.carImage);
}
}
}
FruitTask.java
package cn.edu.hznu.ex5_0.task;
import android.os.AsyncTask;
import java.util.ArrayList;
import cn.edu.hznu.ex5_0.R;
import cn.edu.hznu.ex5_0.bean.FruitItem;
import cn.edu.hznu.ex5_0.bean.FruitResource;
//异常任务中几个方法的执行顺序:onPreExecute()->doInBackground()->onPostExecute()
/**
* Created by 2017810402084 on 2020-04-09.
* 三个泛型:1、第一个泛型的类型根据异步任务执行时传的参数类型
* 2、如果执行异步任务时,需要同步显示相应的进度,则设为Int
* 3、第二个泛型的类型根据异步任务执行结束后结果的类型
*/
public class FruitTask extends AsyncTask<Integer,Void,ArrayList<FruitItem>> {
//4\添加一个属性
private CallBack back;
//5、构造方法
public FruitTask(CallBack back) {
this.back = back;
}
@Override
protected void onPreExecute() {
//在主线程执行
super.onPreExecute();
}
@Override
protected void onProgressUpdate(Void... values) {
//做进度显示的操作
super.onProgressUpdate(values);
}
@Override
protected ArrayList<FruitItem> doInBackground(Integer... integers) {
//Integer... integers 可变参数
//在子线程中执行
ArrayList<FruitItem> data=new ArrayList<>();
for(int i = 0; i< FruitResource.friutNames.length; i++){
double price=5+((int)(Math.random()*100))/10.0;
FruitItem itemData=new FruitItem( FruitResource.fruitImageIds[i], FruitResource.friutNames[i]+":"+integers[0],price, R.drawable.shopping_car);
data.add(itemData);
}
try{
Thread.sleep(2000);
}catch (InterruptedException e){
e.printStackTrace();
}
return data;
}
@Override
protected void onPostExecute(ArrayList<FruitItem> result) {
//在主线程中执行
if(back!=null)
back.getResult(result);
super.onPostExecute(result);
}
public interface CallBack{
void getResult(ArrayList<FruitItem> result); //第三个参数是什么类型就是什么类型
}
}
MainActivity.java
package cn.edu.hznu.ex5_0;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import cn.edu.hznu.ex5_0.adapter.FruitAdapter;
import cn.edu.hznu.ex5_0.bean.FruitItem;
import cn.edu.hznu.ex5_0.task.FruitTask;
public class MainActivity extends AppCompatActivity {
private ListView listView; //定义listview
private ArrayList<FruitItem> data=new ArrayList<>();
private FruitAdapter adapter;
private boolean isLoading=true,isDown=false;
private int curPage=1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView= (ListView) findViewById(R.id.listView); //绑定
//**********************添加带有底部视图**************************************
View view= LayoutInflater.from(this).inflate(R.layout.footer_layout,null);
listView.addFooterView(view);
loadData(); //将列表项的数据加载到数据源(顺序表)中
adapter=new FruitAdapter(MainActivity.this, R.layout.item_layout,data);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, "你选择的水果是:"+data.get(position).getFruitName(), Toast.LENGTH_SHORT).show();
}
});
//添加列表的滚动事件
listView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView absListView, int scrollState) {
if(isDown==true&&scrollState==SCROLL_STATE_IDLE){
loadData();
}
}
@Override
public void onScroll(AbsListView absListView, int i, int i1, int i2) {
if(i+i1==i2){
isDown=true;
}else{
isDown=false;
}
}
});
}
private void loadData() {
if(isLoading){
isLoading=false;
new FruitTask(new FruitTask.CallBack() {
@Override
public void getResult(ArrayList<FruitItem> result) {//重写接接口方法
data.addAll(result);
adapter.notifyDataSetChanged();
}
}).execute(curPage);
isLoading=true;
curPage++;
}
}
}
布局文件
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="cn.edu.hznu.ex5_0.MainActivity">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listView">
</ListView>
</RelativeLayout>
footer_layout.xml
<?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="wrap_content">
<ProgressBar
style="?android:attr/progressBarStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/progressBar"
android:layout_weight="1" />
<TextView
android:text="正在加载数据........"
android:textSize="24sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/textView"
android:layout_weight="1" />
</LinearLayout>
item_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="match_parent">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/apple_pic"
android:id="@+id/fruitImage"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="苹果"
android:textSize="28sp"
android:gravity="center"
android:id="@+id/fruitName"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_weight="4"
android:layout_height="wrap_content"
android:text="12.8元/kg"
android:textSize="28sp"
android:gravity="center"
android:id="@+id/fruitPrice"/>
<ImageView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="match_parent"
android:src="@drawable/shopping_car"
android:id="@+id/carImage"
/>
</LinearLayout>
</LinearLayout>
</LinearLayout>
另外需要10张水果图片需要放在项目的drawable文件夹下!!!
2020-04-09 Android 学习的第六课