ListView 簡介

ListView 是安卓裡常用的控制元件， 本文介紹一下常用用法，以及優化等方法

改寫 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>

新建一個 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 用於 listview 每個元素的檢視

<?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>

新建一個class IconAdapter 繼承自 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
這兒有了一個優化, convertView 將之前的佈局進行快取, 以便之後進行重用.

所以我們判斷convertView是否為空. 空的話就使用LayoutInflater去載入佈局, 否則的話就直接複用convertView

測試listview

MainActivity裡面加入下面程式碼

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);
    }


}

效果圖如下：