ListView实现多种item布局的方法和注意事项
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
- /**
- * 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
- }
- }
分享两张微信、易信的图,你也可以做成这样子。
注意:
使用Listview显示多样视图时,用到了getItemViewType和getViewTypeCount,但是我一运行程序就会报数组越界异常,经过查资料发现,getItemViewType的值一定要从0开始,我开始设置的type类型是从1开始的,结果就悲催了,app一直崩溃,报Java.lang.ArrayIndexOutOfBoundsException。最后把type类型改成从0开始就好了,最后注意一点,getViewTypeCount返回值一定要大于等于getItemViewType的个数。