使用ListView自定义布局

1.新建一个ListViewTest项目

2.修改MainActivity:

package com.example.listviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.AndroidCharacter;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {

    private String[] data = {
            "apple", "bannana", "pear", "orange",
            "apple", "bannana", "pear", "orange",
            "apple", "bannana", "pear", "orange",
            "apple", "bannana", "pear", "orange",
    };


    @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 = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);


    }
}

3.修改activity_main.xml

<?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>

效果展示如下:

image.png

4.使用ListView

新建一个类Fruit:

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 void setName(String name) {
        this.name = name;
    }

    public int getImageId() {
        return imageId;
    }

    public void setImageId(int imageId) {
        this.imageId = imageId;
    }
}

新建一个FruitAdapter:

package com.example.listviewtest;

import android.content.Context;
import android.support.annotation.IdRes;
import android.support.annotation.LayoutRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.text.Layout;
import android.util.Log;
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 static final String TAG = "FruitAdapter";


    private  int resourceId;
    public FruitAdapter( Context context,
                         int textViewResourceId,
                         List<Fruit> objects) {
        super(context,textViewResourceId, objects);
        resourceId = textViewResourceId;

    }


    @NonNull
    @Override
    public View getView(int position,
                        @Nullable View convertView,
                        @NonNull ViewGroup parent) {
        Log.d(TAG, "position: "+position);
        Fruit fruit = getItem(position); //获取当前Fruit实例
        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);

        fruitImage.setImageResource(fruit.getImageId());
        fruitName.setText(fruit.getName());
        return view;
    }
}

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"
    android:orientation="vertical">

    <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>

MainActivity:

package com.example.listviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.AndroidCharacter;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private List<Fruit> fruitList = new ArrayList<>();
    
    @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);


    }

    private void initFruits() {


        for (int i = 0; i <10 ; i++) {

            Fruit apple = new Fruit("apple",R.drawable.apple);
            fruitList.add(apple);
            Fruit orange = new Fruit("orange",R.drawable.orange);
            fruitList.add(orange);



        }

                
    }
}

提升ListView的运行效率

ListView这个控件实际上是很难用的,就是因为它很多细节可以优化,效率就是比较重要的一点.下面我们来优化下它的效率:

FruitAdapter:

package com.example.listviewtest;

import android.content.Context;
import android.support.annotation.IdRes;
import android.support.annotation.LayoutRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.text.Layout;
import android.util.Log;
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 static final String TAG = "FruitAdapter";


    private int resourceId;

    public FruitAdapter(Context context,
                        int textViewResourceId,
                        List<Fruit> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;

    }


    @NonNull
    @Override
    public View getView(int position,
                        @Nullable View convertView,
                        @NonNull ViewGroup parent) {
        Log.d(TAG, "position: " + position);
        Fruit fruit = getItem(position); //获取当前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;
    }


}

这里对convertView进行重用,用viewHolder来取数据,提高了效率.

ListView的点击事件

修改MainActivity:

package com.example.listviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.AndroidCharacter;
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<>();

    @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();
            }
        });

    }

    private void initFruits() {

        for (int i = 0; i <10 ; i++) {

            Fruit apple = new Fruit("apple",R.drawable.apple);
            fruitList.add(apple);
            Fruit orange = new Fruit("orange",R.drawable.orange);
            fruitList.add(orange);

        }
       
    }
}