listView 的优化

[android]代码库

如果每个item的差别比较大的话你可以多定义几个layout，然后再adapter的getView方法中加载不同的layout，如果差别不是特别大的话你可以在同一个layout里面执行控件的显示与隐藏
 ListView具有多种item布局——实现微信对话列
分类： android UI（常用） 2013-12-22 19:35 11603人阅读 评论(37) 收藏 举报
       这篇文章的效果也是大家常见的，各种通讯应用的对话列表都是这种方式，像微信、whatsapp、易信、米聊等。我们这篇文章也权当为回忆，形成简单的笔记。这篇文章参考了2009年Google IO中的《TurboChargeYourUI-How to make your AndroidUI fast and efficient》和2010年Google IO中的《The World of List View》。像2009年Google IO的资料还是很前沿的，那会android开发资料很少，最重要的就是参考google发布的各种资料。

    在《TurboChargeYourUI-How to make your AndroidUI fast and efficient》介绍了怎样提高listview的性能，优化了listview的加载速度。这里的item使用的是单一布局，能够实现view的重用和回收，那么多种布局文件的怎么办呢，如果再使用上面的方法，view的重用会出现问题，Android使用的BaseAdapter提供了解决多种布局文件的重用方法。
1）重写 getViewTypeCount() – 该方法返回多少个不同的布局

2）重写 getItemViewType(int) – 根据position返回相应的Item





[java] view plaincopyprint?在CODE上查看代码片派生到我的代码片
/** 
 * 比原来的多了getItemViewType和getViewTypeCount这两个方法， 
 *  
 * */  
public class ChatAdapter extends BaseAdapter {  
  
    public static final String KEY = "key";  
    public static final String VALUE = "value";  
  
    public static final int VALUE_TIME_TIP = 0;// 7种不同的布局  
    public static final int VALUE_LEFT_TEXT = 1;  
    public static final int VALUE_LEFT_IMAGE = 2;  
    public static final int VALUE_LEFT_AUDIO = 3;  
    public static final int VALUE_RIGHT_TEXT = 4;  
    public static final int VALUE_RIGHT_IMAGE = 5;  
    public static final int VALUE_RIGHT_AUDIO = 6;  
    private LayoutInflater mInflater;  
  
    private List<Message> myList;  
  
    public ChatAdapter(Context context, List<Message> myList) {  
        this.myList = myList;  
  
        mInflater = (LayoutInflater) context  
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);  
    }  
  
    @Override  
    public int getCount() {  
        return myList.size();  
    }  
  
    @Override  
    public Object getItem(int arg0) {  
        return myList.get(arg0);  
    }  
  
    @Override  
    public long getItemId(int arg0) {  
        return arg0;  
    }  
  
    @Override  
    public View getView(int position, View convertView, ViewGroup arg2) {  
  
        Message msg = myList.get(position);  
        int type = getItemViewType(position);  
        ViewHolderTime holderTime = null;  
        ViewHolderRightText holderRightText = null;  
        ViewHolderRightImg holderRightImg = null;  
        ViewHolderRightAudio holderRightAudio = null;  
        ViewHolderLeftText holderLeftText = null;  
        ViewHolderLeftImg holderLeftImg = null;  
        ViewHolderLeftAudio holderLeftAudio = null;  
          
        if (convertView == null) {  
            switch (type) {  
            case VALUE_TIME_TIP:  
                holderTime = new ViewHolderTime();  
                convertView = mInflater.inflate(R.layout.list_item_time_tip,  
                        null);  
                holderTime.tvTimeTip = (TextView) convertView  
                        .findViewById(R.id.tv_time_tip);  
                holderTime.tvTimeTip.setText(msg.getValue());  
                convertView.setTag(holderTime);  
                break;  
            // 左边  
            case VALUE_LEFT_TEXT:  
                holderLeftText = new ViewHolderLeftText();  
                convertView = mInflater.inflate(R.layout.list_item_left_text,  
                        null);  
                holderLeftText.ivLeftIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderLeftText.btnLeftText = (Button) convertView  
                        .findViewById(R.id.btn_left_text);  
                holderLeftText.btnLeftText.setText(msg.getValue());  
                convertView.setTag(holderLeftText);  
                break;  
  
            case VALUE_LEFT_IMAGE:  
                holderLeftImg = new ViewHolderLeftImg();  
                convertView = mInflater.inflate(R.layout.list_item_left_iamge,  
                        null);  
                holderLeftImg.ivLeftIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderLeftImg.ivLeftImage = (ImageView) convertView  
                        .findViewById(R.id.iv_left_image);  
                holderLeftImg.ivLeftImage.setImageResource(R.drawable.test);  
                convertView.setTag(holderLeftImg);  
                break;  
  
            case VALUE_LEFT_AUDIO:  
                holderLeftAudio = new ViewHolderLeftAudio();  
                convertView = mInflater.inflate(R.layout.list_item_left_audio,  
                        null);  
                holderLeftAudio.ivLeftIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderLeftAudio.btnLeftAudio = (Button) convertView  
                        .findViewById(R.id.btn_left_audio);  
                holderLeftAudio.tvLeftAudioTime = (TextView) convertView  
                        .findViewById(R.id.tv_left_audio_time);  
                holderLeftAudio.tvLeftAudioTime.setText(msg.getValue());  
                convertView.setTag(holderLeftAudio);  
                break;  
            // 右边  
            case VALUE_RIGHT_TEXT:  
                holderRightText= new ViewHolderRightText();  
                convertView = mInflater.inflate(R.layout.list_item_right_text,  
                        null);  
                holderRightText.ivRightIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderRightText.btnRightText = (Button) convertView  
                        .findViewById(R.id.btn_right_text);  
                holderRightText.btnRightText.setText(msg.getValue());  
                convertView.setTag(holderRightText);  
                break;  
  
            case VALUE_RIGHT_IMAGE:  
                holderRightImg= new ViewHolderRightImg();  
                convertView = mInflater.inflate(R.layout.list_item_right_iamge,  
                        null);  
                holderRightImg.ivRightIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderRightImg.ivRightImage = (ImageView) convertView  
                        .findViewById(R.id.iv_right_image);  
                holderRightImg.ivRightImage.setImageResource(R.drawable.test);  
                convertView.setTag(holderRightImg);  
                break;  
  
            case VALUE_RIGHT_AUDIO:  
                holderRightAudio=new ViewHolderRightAudio();  
                convertView = mInflater.inflate(R.layout.list_item_right_audio,  
                        null);  
                holderRightAudio.ivRightIcon = (ImageView) convertView  
                        .findViewById(R.id.iv_icon);  
                holderRightAudio.btnRightAudio = (Button) convertView  
                        .findViewById(R.id.btn_right_audio);  
                holderRightAudio.tvRightAudioTime = (TextView) convertView  
                        .findViewById(R.id.tv_right_audio_time);  
                holderRightAudio.tvRightAudioTime.setText(msg.getValue());  
                convertView.setTag(holderRightAudio);  
                break;  
  
            default:  
                break;  
            }  
              
        } else {  
            Log.d("baseAdapter", "Adapter_:"+(convertView == null) );  
            switch (type) {  
            case VALUE_TIME_TIP:  
                holderTime=(ViewHolderTime)convertView.getTag();  
                holderTime.tvTimeTip.setText(msg.getValue());  
                break;  
            case VALUE_LEFT_TEXT:  
                holderLeftText=(ViewHolderLeftText)convertView.getTag();  
                holderLeftText.btnLeftText.setText(msg.getValue());  
                break;  
            case VALUE_LEFT_IMAGE:  
                holderLeftImg=(ViewHolderLeftImg)convertView.getTag();  
                holderLeftImg.ivLeftImage.setImageResource(R.drawable.test);  
                break;  
            case VALUE_LEFT_AUDIO:  
                holderLeftAudio=(ViewHolderLeftAudio)convertView.getTag();  
                holderLeftAudio.tvLeftAudioTime.setText(msg.getValue());  
                break;  
            case VALUE_RIGHT_TEXT:  
                holderRightText=(ViewHolderRightText)convertView.getTag();  
                holderRightText.btnRightText.setText(msg.getValue());  
                break;  
            case VALUE_RIGHT_IMAGE:  
                holderRightImg=(ViewHolderRightImg)convertView.getTag();  
                holderRightImg.ivRightImage.setImageResource(R.drawable.test);  
                break;  
            case VALUE_RIGHT_AUDIO:  
                holderRightAudio=(ViewHolderRightAudio)convertView.getTag();  
                holderRightAudio.tvRightAudioTime.setText(msg.getValue());  
                break;  
  
            default:  
                break;  
            }  
              
            //holder = (ViewHolder) convertView.getTag();  
        }  
        return convertView;  
    }  
  
    /** 
     * 根据数据源的position返回需要显示的的layout的type 
     *  
     * type的值必须从0开始 
     *  
     * */  
    @Override  
    public int getItemViewType(int position) {  
  
        Message msg = myList.get(position);  
        int type = msg.getType();  
        Log.e("TYPE:", "" + type);  
        return type;  
    }  
  
    /** 
     * 返回所有的layout的数量 
     *  
     * */  
    @Override  
    public int getViewTypeCount() {  
        return 7;  
    }  
  
    class ViewHolderTime {  
        private TextView tvTimeTip;// 时间  
    }  
  
    class ViewHolderRightText {  
        private ImageView ivRightIcon;// 右边的头像  
        private Button btnRightText;// 右边的文本  
    }  
  
    class ViewHolderRightImg {  
        private ImageView ivRightIcon;// 右边的头像  
        private ImageView ivRightImage;// 右边的图像  
    }  
  
    class ViewHolderRightAudio {  
        private ImageView ivRightIcon;// 右边的头像  
        private Button btnRightAudio;// 右边的声音  
        private TextView tvRightAudioTime;// 右边的声音时间  
    }  
  
    class ViewHolderLeftText {  
        private ImageView ivLeftIcon;// 左边的头像  
        private Button btnLeftText;// 左边的文本  
    }  
  
    class ViewHolderLeftImg {  
        private ImageView ivLeftIcon;// 左边的头像  
        private ImageView ivLeftImage;// 左边的图像  
    }  
  
    class ViewHolderLeftAudio {  
        private ImageView ivLeftIcon;// 左边的头像  
        private Button btnLeftAudio;// 左边的声音  
        private TextView tvLeftAudioTime;// 左边的声音时间  
    }  
  
}