深入淺出學習Android ListView基礎

ListView 簡介

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

1、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>

2、新建一個javabean

package com.example.tomchen.testlistview;
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;
  }
}

3、新建icon_item.xml 用於 listview 每個元素的視圖

<?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>

4、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;

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 將之前的布局進行緩存, 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去加載布局, 否則的話就直接復用convertView

測試listview

MainActivity裡面加入下面代碼

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：

以上就是本文的全部內容，希望對大家的學習Android程序設計有所幫助。