Android ListView 基础入门 简介以及深入优化

ListView 简介

ListView 是安卓里常用的控件， 本文介绍一下常用用法，以及优化等方法

本文地址 http://blog.csdn.net/never_cxb/article/details/48159717。转载请注明出处

改写 activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <ListView        android:id="@+id/listview"        android:layout_width="match_parent"        android:layout_height="match_parent" /></LinearLayout>

新建一个 javabean

package com.example.tomchen.testlistview;/** * Created by tomchen on 9/1/15. */public class Icon {    private int imageId;    private String name;    public Icon(String name, int imageId) {        this.name = name;        this.imageId = imageId;    }    public String getName() {        return name;    }    public int getImageId() {        return imageId;    }}

新建icon_item.xml 用于 listview 每个元素的视图

<?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="horizontal">    <TextView        android:id="@+id/text"        android:layout_width="wrap_content"        android:layout_height="match_parent" />    <ImageView        android:id="@+id/icon"        android:layout_width="wrap_content"        android:layout_height="match_parent" /></LinearLayout>

新建一个class IconAdapter 继承自 ArrayAdapter

package com.example.tomchen.testlistview;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;/** * Created by tomchen on 9/1/15. */public class IconAdapter extends ArrayAdapter<Icon> {    private int resourceId;    public IconAdapter(Context context, int resource, List<Icon> icons) {        super(context, resource, icons);        this.resourceId = resource;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        Icon icon = getItem(position);        View view;        if (convertView == null) {            view = LayoutInflater.from(getContext()).inflate(resourceId, null);        } else {            view = convertView;        }        ImageView image = (ImageView) view.findViewById(R.id.icon);        image.setImageResource(icon.getImageId());        TextView text = (TextView) view.findViewById(R.id.text);        text.setText(icon.getName());        return view;    }}

Note
这儿有了一个优化, convertView 将之前的布局进行缓存, 以便之后进行重用.

所以我们判断convertView是否为空. 空的话就使用LayoutInflater去加载布局, 否则的话就直接复用convertView

关于 ArrayAdapter 可以参阅这篇博客
Android ArrayAdapter 源码查看 深入了解

测试listview

MainActivity里面加入下面代码

package com.example.tomchen.testlistview;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private ListView listView;    private List<Icon> icons = new ArrayList<Icon>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        listView = (ListView) findViewById(R.id.listview);        icons.add(new Icon("Icon_01", R.drawable.ic_01));        icons.add(new Icon("Icon_02", R.drawable.ic_02));        icons.add(new Icon("Icon_03", R.drawable.ic_03));        icons.add(new Icon("Icon_04", R.drawable.ic_04));        icons.add(new Icon("Icon_05", R.drawable.ic_05));        icons.add(new Icon("Icon_06", R.drawable.ic_06));        icons.add(new Icon("Icon_07", R.drawable.ic_07));        icons.add(new Icon("Icon_08", R.drawable.ic_08));        icons.add(new Icon("Icon_09", R.drawable.ic_09));        IconAdapter adapter = new IconAdapter(this, R.layout.icon_item, icons);        listView.setAdapter(adapter);    }}

效果图如下：