[置顶] Android(安卓)ListView 基础入门 简介以及深入优化
16lz
2021-01-25
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); }}更多相关文章
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