Android ListView, Object reuse example

안드로이드에서 ListView를 사용할 때 객체를 재활용하여 성능을 올리고 메모리 사용을 낮추는 예

객체를 재활용할 때 부주의하면 발생할 수 있는 현상을 확인해본다. ListView를  위 아래로 스크롤할 때 선택된 체크박스의 위치가 불규칙하게 변경되는 문제를 확인할 수 있다. 이 문제를 해결한 예는 여기를 참조하세요

layout/main.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" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#cccccc"
        android:text="" />

    <ListView
        android:id="@+id/listView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</LinearLayout>

layout/row.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="wrap_content"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

    <CheckBox
        android:id="@+id/checkBox1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CheckBox" />

</LinearLayout>

TestActivity.java

package com.example.androidapp;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class TestActivity extends Activity implements OnItemClickListener {

	String [] name = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L",
			"M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"};
	ArrayAdapter<String> adapter;
	TextView tv;
	ListView listView;
	
    public void onCreate(Bundle icicle) {
         super.onCreate(icicle);
         setContentView(R.layout.main);
         
         adapter = new MyAdapter ( this, 
         		 R.layout.row, R.id.textView1, name);
         
         listView = (ListView) findViewById(R.id.listView1);

         listView.setAdapter(adapter);
         listView.setOnItemClickListener(this);

         tv = (TextView) findViewById(R.id.textView1);
    }

    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
	TextView tv = (TextView) v.findViewById(R.id.textView1);
	String name = tv.getText().toString();
	this.tv.setText(name);
    }

} 

MyAdapter.java

package com.example.androidapp;

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.ImageView;
import android.widget.TextView;

public class MyAdapter extends ArrayAdapter<String> {
	Context context;
	public MyAdapter(Context context, int textViewResourceId, String[] objects) {
		super(context, textViewResourceId, objects);
		this.context = context;
	}

	public MyAdapter(Context context, int resource, int textViewResourceId,
			String[] objects) {
		super(context, resource, textViewResourceId, objects);
		this.context = context;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		View view = convertView;
		if(view==null) {
			Activity ctx = (Activity) this.context;
			LayoutInflater inflater =ctx.getLayoutInflater();
		    view = inflater.inflate(R.layout.row, null);
		}
		ImageView iv = (ImageView) view.findViewById(R.id.imageView1);
		TextView tv = (TextView) view.findViewById(R.id.textView1);
		CheckBox cb = (CheckBox) view.findViewById(R.id.checkBox1);
                tv = (TextView) findViewById(R.id.textView1);
		return view;
	}

}