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使用ViewHolder模式来提高自定义adapter的效率

来源：互联网 发布：淘宝服务市场 第三方 编辑：程序博客网 时间：2024/04/30 10:05

ViewHolder不是Android的开发API，而是一种设计方法，就是设计个静态类，缓存一下，省得Listview更新的时候，还要重新操作。

在自定义adapter时，我们得到view时可以用


这是最慢的加载方式，每一次都重新定义一个View载入布局，再加载数据。我们可以用下面两种方式，先看第一种：
这种方式又可以提高50%的效率，定义了一个ViewHolder，将arg1的tag设置为ViewHolder,不为空时重新使用即可。
了解了以上三种方式后，我们看一个完整的小项目来加强下理解
1、首先我们新建一个layout文件：interview_people.xml
public View getView(int arg0, View arg1, ViewGroup arg2) {// TODO Auto-generated method stub        if(arg1==null){arg1 = mInflater.inflate(R.layout.interview_item, null);        }take_photo = (ImageButton) arg1.findViewById(R.id.take_photo);// take_photo.setOnClickListener((InterviewPeople) this.context);take_photo.setOnClickListener(new lvbuttonListener(context, arg0));eventtime = (TextView) arg1.findViewById(R.id.eventtime);infocontent = (TextView) arg1.findViewById(R.id.EVENTDISCRIBE);photo = (ImageView) arg1.findViewById(R.id.imageview01);// eventtime.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDATE")));if (listItems.get(arg0).get("EVENTDATE") != null) {eventtime.setText(listItems.get(arg0).get("EVENTDATE").toString());} else {DatePickerHelper datepickerHelper = new DatePickerHelper();eventtime.setText(datepickerHelper.getDate());}if (listItems.get(arg0).get("IMGPATH") != null) {String str = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/"+ listItems.get(arg0).get("IMGPATH").toString();File file = new File(str);if(file.exists()){photo.setImageURI(Uri.parse(str));// 将取得的照片设置到控件//20120114080708.jpg}else{photo.setImageBitmap(ImageView01.getHttpBitmap(url+ listItems.get(arg0).get("IMGPATH")));}}infocontent.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDISCRIBE")));return arg1;}
这种方式可以提高200%的速度，arg1不为空的时候直接重新使用arg1从而减少了很多不必要的View的创建，然后加载数据,但是这种还可以改进，
再看下面这种方式：
public View getView(int arg0, View arg1, ViewGroup arg2) {// TODO Auto-generated method stubViewHolder holder;        if(arg1==null){arg1 = mInflater.inflate(R.layout.interview_item, null);holder=new ViewHolder();holder.eventtime=(TextView)arg1.findViewById(R.id.eventtime);holder.infocontent=(TextView)arg1.findViewById(R.id.EVENTDISCRIBE);holder.photo=(ImageView)arg1.findViewById(R.id.imageview01);holder.take_photo=(ImageButton)arg1.findViewById(R.id.take_photo);holder.take_photo.setOnClickListener(new lvbuttonListener(context, arg0));arg1.setTag(holder);        }else{        holder=(ViewHolder)arg1.getTag();        }// eventtime.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDATE")));if (listItems.get(arg0).get("EVENTDATE") != null) {holder.eventtime.setText(listItems.get(arg0).get("EVENTDATE").toString());} else {DatePickerHelper datepickerHelper = new DatePickerHelper();holder.eventtime.setText(datepickerHelper.getDate());}if (listItems.get(arg0).get("IMGPATH") != null) {String str = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/"+ listItems.get(arg0).get("IMGPATH").toString();File file = new File(str);if(file.exists()){holder.photo.setImageURI(Uri.parse(str));// 将取得的照片设置到控件}else{holder.photo.setImageBitmap(ImageView01.getHttpBitmap(url+ listItems.get(arg0).get("IMGPATH")));}}holder.infocontent.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDISCRIBE")));return arg1;}这是最慢的加载方式，每一次都重新定义一个View载入布局，再加载数据。
我们可以用下面两种方式，先看第一种：public View getView(int arg0, View arg1, ViewGroup arg2) {// TODO Auto-generated method stub if(arg1==null){arg1 = mInflater.inflate(R.layout.interview_item, null); }take_photo = (ImageButton) arg1.findViewById(R.id.take_photo);// take_photo.setOnClickListener((InterviewPeople) this.context);take_photo.setOnClickListener(new lvbuttonListener(context, arg0));eventtime = (TextView) arg1.findViewById(R.id.eventtime);infocontent = (TextView) arg1.findViewById(R.id.EVENTDISCRIBE);photo = (ImageView) arg1.findViewById(R.id.imageview01);// eventtime.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDATE")));if (listItems.get(arg0).get("EVENTDATE") != null) {eventtime.setText(listItems.get(arg0).get("EVENTDATE").toString());} else {DatePickerHelper datepickerHelper = new DatePickerHelper();eventtime.setText(datepickerHelper.getDate());}if (listItems.get(arg0).get("IMGPATH") != null) {String str = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/"+ listItems.get(arg0).get("IMGPATH").toString();File file = new File(str);if(file.exists()){photo.setImageURI(Uri.parse(str));// 将取得的照片设置到控件//20120114080708.jpg}else{photo.setImageBitmap(ImageView01.getHttpBitmap(url+ listItems.get(arg0).get("IMGPATH")));}}infocontent.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDISCRIBE")));return arg1;}这种方式可以提高200%的速度，arg1不为空的时候直接重新使用arg1从而减少了很多不必要的View的创建，然后加载数据,但是这种还可以改进，再看下面这种方式：
public View getView(int arg0, View arg1, ViewGroup arg2) {// TODO Auto-generated method stubViewHolder holder; if(arg1==null){arg1 = mInflater.inflate(R.layout.interview_item, null);holder=new ViewHolder();holder.eventtime=(TextView)arg1.findViewById(R.id.eventtime);holder.infocontent=(TextView)arg1.findViewById(R.id.EVENTDISCRIBE);holder.photo=(ImageView)arg1.findViewById(R.id.imageview01);holder.take_photo=(ImageButton)arg1.findViewById(R.id.take_photo);holder.take_photo.setOnClickListener(new lvbuttonListener(context, arg0));arg1.setTag(holder); }else{ holder=(ViewHolder)arg1.getTag(); }// eventtime.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDATE")));if (listItems.get(arg0).get("EVENTDATE") != null) {holder.eventtime.setText(listItems.get(arg0).get("EVENTDATE").toString());} else {DatePickerHelper datepickerHelper = new DatePickerHelper();holder.eventtime.setText(datepickerHelper.getDate());}if (listItems.get(arg0).get("IMGPATH") != null) {String str = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/"+ listItems.get(arg0).get("IMGPATH").toString();File file = new File(str);if(file.exists()){holder.photo.setImageURI(Uri.parse(str));// 将取得的照片设置到控件}else{holder.photo.setImageBitmap(ImageView01.getHttpBitmap(url+ listItems.get(arg0).get("IMGPATH")));}}holder.infocontent.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDISCRIBE")));return arg1;}

 
2、再新建一个业务类，也就是自定义的adapter类，自定义的adapter必须继承BaseAdapter类
 
public class MyListviewAdapter extends BaseAdapter {private Context context; // 运行上下文private LayoutInflater mInflater;private List<Map<String, Object>> listItems;private TextView eventtime;private TextView infocontent;private ImageView photo;private ImageButton take_photo;private String MAPID = "";private String USERNAME = "";private String EVENTDISCRIBE = "";private String url = "http://"+ "220.178.224.44/webservices/RESOURSE/ZZWW/log/";private String strPath="";public MyListviewAdapter() {}public MyListviewAdapter(Context context,List<Map<String, Object>> listItems) {this.context = context;mInflater = LayoutInflater.from(this.context);this.listItems = listItems;// 创建视图容器并设置上下文//}@Overridepublic View getView(int arg0, View arg1, ViewGroup arg2) {// TODO Auto-generated method stubViewHolder holder;        if(arg1==null){arg1 = mInflater.inflate(R.layout.interview_item, null);holder=new ViewHolder();holder.eventtime=(TextView)arg1.findViewById(R.id.eventtime);holder.infocontent=(TextView)arg1.findViewById(R.id.EVENTDISCRIBE);holder.photo=(ImageView)arg1.findViewById(R.id.imageview01);holder.take_photo=(ImageButton)arg1.findViewById(R.id.take_photo);holder.take_photo.setOnClickListener(new lvbuttonListener(context, arg0));arg1.setTag(holder);        }else{        holder=(ViewHolder)arg1.getTag();        }if (listItems.get(arg0).get("EVENTDATE") != null) {holder.eventtime.setText(listItems.get(arg0).get("EVENTDATE").toString());} else {DatePickerHelper datepickerHelper = new DatePickerHelper();holder.eventtime.setText(datepickerHelper.getDate());}if (listItems.get(arg0).get("IMGPATH") != null) {String str = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/"+ listItems.get(arg0).get("IMGPATH").toString();File file = new File(str);if(file.exists()){holder.photo.setImageURI(Uri.parse(str));// 将取得的照片设置到控件//20120114080708.jpg}else{ holder.photo.setImageBitmap(ImageView01.getHttpBitmap(url+ listItems.get(arg0).get("IMGPATH")));}}holder.infocontent.setText(UserInfo.translateNullString(listItems.get(arg0).get("EVENTDISCRIBE")));return arg1;}class lvbuttonListener implements OnClickListener {private int position;private Context context;               lvbuttonListener(Context context, int position) {this.context = context;this.position = position;}@Overridepublic void onClick(View v) {// TODO Auto-generated method stub}}static class ViewHolder {ImageButton take_photo ;TextView eventtime ;TextView infocontent ;ImageView photo ;}public void addItem(Map map) {// TODO Auto-generated method stublistItems.add(0, map);}public void setStrPath(String strPath){this.strPath=strPath;}public void deleteItem() {int size = listItems.size();if (size > 0) {listItems.remove(listItems.size() - 1);}}public int getCount() {// TODO Auto-generated method stubif (listItems.size() != 0) {return listItems.size();} else {return 0;}}public Object getItem(int arg0) {// TODO Auto-generated method stubreturn arg0;}public long getItemId(int arg0) {// TODO Auto-generated method stubreturn arg0;}

 
 
这个业务类继承了BaseAdapter类，定义了一个静态内部类ViewHolder，上面的 lvbuttonListener内部类实现了OnClickListener接口，通过此类的构造方法，可以初始化position和context等变量。
3、接下来是第三步，新建一个activity,用来控制相关的逻辑。
public class InterviewPeople extends Activity implements OnClickListener 
{private ListView listview;private EditText interview;
private TextView textview01 = null;
private Button sendinterview;
private Button choose_user = null;
private Button take_photos=null;
private Button delete = null;
private Button amplify = null;private String interviewedit = "";private MyListviewAdapter listViewAdapter;private List<Map<String, Object>> listItems;private ImageButton take_photo;private Integer currentFile = 0;// 当前文件的位置private ImageView photo_iv = null;private TableLayout tablelayout01 = null;// private static final int RESULT_CAPTURE_IMAGE = 0;private String strPath = Environment.getExternalStorageDirectory().toString()+ "/CONSDCGMPIC/";// 存放照片的文件夹;// 文件绝对路径private List<String> lPath = null;// 文件的绝对路径数组private List<String> lNamePath = null;// 文件的绝对路径数组private String fileName = null;private String photo_upload_name = "";private String dbimagename = null;private String MSG = "";private boolean flag = false;private int select = 0;private final int MENU_CHOOSE_INTERVIEWER = 0;private final int TAKE_PHOTO = 1;private static final int RESULT_CAPTURE_IMAGE = 0;// 照相的requestCodeprivate static final int REQUEST_CODE_TAKE_VIDEO = 1;private static final int RESULT_CAPTURE_RECORDER_SOUND = 2;// 录音private static final int RESULT_CODE_PASS = 3;private Map<String, Object> wholeresult = null;File file = new File(strPath);@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);setContentView(R.layout.interview_people);listview = (ListView) findViewById(R.id.listview_interview);interview = (EditText) findViewById(R.id.edittext_interview);textview01 = (TextView) findViewById(R.id.textview01);sendinterview = (Button) findViewById(R.id.interview_button);sendinterview.setOnClickListener(this);choose_user=(Button)findViewById(R.id.choose_users);choose_user.setOnClickListener(this);take_photos=(Button)findViewById(R.id.take_photos);take_photos.setOnClickListener(this); tablelayout01 = (TableLayout) findViewById(R.id.tablelayout01);delete = (Button) findViewById(R.id.delete);amplify = (Button) findViewById(R.id.amplify);amplify.setVisibility(View.INVISIBLE);delete.setOnClickListener(this);amplify.setOnClickListener(this);query();}private void query() {// TODO Auto-generated method stub        listItems = getResult();//IMGPATH=20120113155949.jpgif (listItems != null) {listViewAdapter = new MyListviewAdapter(this, listItems);//listViewAdapter.setStrPath(strPath);listview.setAdapter(listViewAdapter);// 创建适配器} else {new AlertDialog.Builder(this).setTitle("提示：").setMessage("没有查询到相关信息！").setPositiveButton("确定",new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog,int which) {// TODO Auto-generated method stub}}).show();}}private List<Map<String, Object>> getResult() {// TODO Auto-generated method stubMap<String, Object> params = new HashMap<String, Object>();params.put("MAPID", UserInfo.getMapID());SoapObject Result = null;try {Result = WSUtil.getSoapObjectByCallingWS(//此处用到android的webservice知识WebServiceConfig.NAMESPACE, "interview", params,WebServiceConfig.wsdl);} catch (Exception e) {return null;}if (Result != null) {SoapObject dataSet = WSObjectUtil.getDataSetObject(Result);if (dataSet == null) {return null;}List<Map<String, Object>> s = WSObjectMapUtil.getRowMapList(dataSet);return s;} else {return null;}}

 
好的，看下效果图：
 
注意：上面用到了android的webservices的知识，这里不做介绍，以后会专门列出时间给大家讲解。
	
				
		









 淘宝服务市场 第三方
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