android ListView优化

android ListView通过优化重用历史缓存实现。listview相应的数据适配器一般使用自己定义BaseAdapter子类，重用历史缓冲区来提高性能。

例如，下面的示例代码演示：

1、listView数据适配器

/**
	 * 待处理请假信息的数据适配器类
	 * @author yqq
	 *
	 */
	private  class LeaveInfoAdapter extends BaseAdapter{

		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return mleaveInfos.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return mleaveInfos.get(position);
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
				View view=null;
			ViewHolder holder=null;
			if (convertView!=null && convertView instanceof LinearLayout) {
				view=convertView;
				holder=(ViewHolder) view.getTag();

			}else{
				view=View.inflate(getApplicationContext(), R.layout.leave_info_item, null);
				holder=new ViewHolder();
				holder.name=(TextView)view.findViewById(R.id.tv_name);
				holder.workIdAndDepartment=(TextView)view.findViewById(R.id.tv_workid_depart);
				holder.leaveinfo=(TextView)view.findViewById(R.id.tv_leave_info);
				holder.date=(TextView)view.findViewById(R.id.tv_date);
				holder.endDate=(TextView)view.findViewById(R.id.tv_endtime);
				view.setTag(holder);

			}
			LeaveInfo info=mleaveInfos.get(position);
			Log.i("測试",info.toString());
			holder.name.setText(info.getName());
			holder.workIdAndDepartment.setText("(工号:"+info.getWorkId()+"部门:"+info.getDepartment()+")");
			holder.leaveinfo.setText(info.getLeaveInfo());
			holder.date.setText("假期起止:"+info.getLeaveData()+"\n");
			holder.endDate.setText("-"+info.getEndleaveDate());

			return view;
		}

	}

	private static class ViewHolder{
		TextView name;//员工姓名显示控件
		TextView workIdAndDepartment;//员工工号和部门显示
		TextView leaveinfo;//员工请假信息
		TextView date;//员工请假日期
		TextView endDate;

	}

2、每项数据显示的布局

leave_info_item.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"

     >
     <LinearLayout
          android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"

         >
            <ImageView
        android:id="@+id/iv_headcolor"
        android:layout_width="wrap_content"
        android:layout_height="80dp"
        android:src="@drawable/light_green" />

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="5dp" >

                <TextView
                    android:id="@+id/tv_name"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="姓名"
                    android:textColor="#ff0000"
                    android:textSize="15sp" />

                <TextView
                    android:id="@+id/tv_leave_info"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/tv_name"
                    android:paddingTop="8dp"
                    android:text="请假理由"
                    android:textSize="20sp" />

                <TextView
                    android:id="@+id/tv_date"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_above="@+id/tv_leave_info"
                    android:layout_alignParentRight="true"
                    android:text="日期"
                    android:textColor="#000000"
                    android:textSize="10sp" />
                 <TextView
                    android:id="@+id/tv_endtime"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                  android:layout_below="@+id/tv_date"

                   android:layout_alignParentRight="true"
                    android:text="日期2"
                    android:textColor="#000000"
                    android:textSize="10sp" />

                <TextView
                    android:id="@+id/tv_workid_depart"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentTop="true"
                    android:layout_toRightOf="@+id/tv_name"
                    android:gravity="center_horizontal"
                    android:paddingLeft="5dp"
                    android:text="姓名和部门"
                    android:textColor="#0000ff"
                    android:textSize="13sp" />

            </RelativeLayout>

     </LinearLayout>

    <View
         android:layout_width="match_parent"
        android:layout_height="2dp"
        android:background="@android:drawable/divider_horizontal_dark"
        />

</LinearLayout>

3、利用异步任务载入数据

/**
	 * 使用异步载入数据，填充待处理请假信息listView
	 */
	private void fillData(){
		new AsyncTask<Void,Void,Void>() {

			@Override
			protected void onPostExecute(Void result) {

				if(mAdapter==null){
					mAdapter=new LeaveInfoAdapter();
					//设置数据适配器
					mLVleaveInfos.setAdapter(mAdapter);
					Log.i("測试", "异步任务显示后台获得数据库数据");
					}
				else {
					mAdapter.notifyDataSetChanged();

				}

				super.onPostExecute(result);
			}

			@Override
			protected Void doInBackground(Void... params) {
				//获得要显示的数据
				mleaveInfos=mLeaveInfosDao.findAll();
				if (mleaveInfos==null) {
					Toast.makeText(HomeActivity.this,"请假数据不存在或是已经清除！

", 500).show();

				}

				Log.i("測试", "异步任务后台获得数据库数据"+mleaveInfos.size());

				return null;
			}
		}.execute();

	}
	

4、为列表每项绑定事件监听

mLVleaveInfos.setOnItemClickListener(new OnItemClickListener() {

			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				Object object=mLVleaveInfos.getItemAtPosition(position);
				Log.i("允许測试",object+"");
				if(object instanceof LeaveInfo){
					tmpInfo=(LeaveInfo)object;
					Log.i("允许測试",tmpInfo.toString());
					showAcceptOrNo();
				}

			}});

5、列表的其它监听和分页载入对于本地数据不须要分页载入，对于server端数据应该分页载入节省流量。

//下拉列表的时候分页载入数据
		mRubishSms.setOnScrollListener(new OnScrollListener() {

			@Override
			public void onScrollStateChanged(AbsListView view, int scrollState) {
				switch (scrollState) {
				//在下拉列表空暇的时候显示数据
				case OnScrollListener.SCROLL_STATE_IDLE:
					//获得分页载入的每页最大值
					int position=mRubishSms.getLastVisiblePosition();
					int total=0;
					if(mInfos!=null){
						// total=maxNum;
						total=mInfos.size();

					}

					if(position==total-1){
						//到达该分页载入的末尾位置
						offset+=maxNum;
						if(offset>totalNums){
							Toast.makeText(RubishSmsActivity.this,"数据已经载入完。没有很多其它的数据了...", 300).show();
							return;

						}
						//异步任务载入数据
						fillData();

					}

					break;

				}

			}

			@Override
			public void onScroll(AbsListView view, int firstVisibleItem,
					int visibleItemCount, int totalItemCount) {
				// TODO Auto-generated method stub

			}
		});

		fillData();

		//每一个条目绑定监听
		mRubishSms.setOnItemClickListener(new OnItemClickListener() {

			View m_view=View.inflate(RubishSmsActivity.this,R.layout.show_rubish_sms_operation,null);
			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				//获得条目相应的每一个对象

			Object object=mRubishSms.getItemAtPosition(position);
			if(object instanceof RubishSmsInfo){
				final RubishSmsInfo info=(RubishSmsInfo) object;
				//对对象的操作1、删除2、恢复到收件箱3、增加黑名单
				Dialog builder=new Dialog(RubishSmsActivity.this);
				builder.setTitle("提示");
				builder.setContentView(m_view);

				//删除
				((TextView)m_view.findViewById(R.id.tv_delete)).setOnClickListener(new OnClickListener() {

					@Override
					public void onClick(View v) {
						mInfos.remove(info);
						if(mRubishSmsInfoDao==null){
							mRubishSmsInfoDao=new RubishSmsInfoDao(getApplicationContext());

						}
						mRubishSmsInfoDao.deleteSmsInfos(info);
						if(mAdapter==null){
							mAdapter=new RubishSmsInfosAdapter();
							mRubishSms.setAdapter(mAdapter);
						}else{
							mAdapter.notifyDataSetChanged();
						}

					}
				});
				//恢复到收件箱
				((TextView)m_view.findViewById(R.id.tv_recovery_sms)).setOnClickListener(new OnClickListener() {

					@Override
					public void onClick(View v) {

					}

				});
				//增加黑名单
				((TextView)m_view.findViewById(R.id.tv_add_black_number)).setOnClickListener(new OnClickListener() {

					@Override
					public void onClick(View v) {

					}
				});

				builder.show();

			}

			}

		});

	}
	

6、BaseExpandableListAdapter演示样例demo:

public class CommonNumberActivity extends Activity {
	private ExpandableListView elv;
	private List<String> groupNames;
	private Map<Integer, List<String>> childrenCacheInfos;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		childrenCacheInfos = new HashMap<Integer, List<String>>();
		setContentView(R.layout.activity_common_num);
		elv = (ExpandableListView) findViewById(R.id.elv);
		elv.setAdapter(new MyAdapter());

		elv.setOnChildClickListener(new OnChildClickListener() {

			@Override
			public boolean onChildClick(ExpandableListView parent, View v,
					int groupPosition, int childPosition, long id) {
				Intent intent = new Intent();
				intent.setAction(Intent.ACTION_DIAL);
				String number = childrenCacheInfos.get(groupPosition).get(childPosition).split("\n")[1];
				intent.setData(Uri.parse("tel:"+number));
				startActivity(intent);
				return false;
			}
		});
	}

	private class MyAdapter extends BaseExpandableListAdapter {

		// 返回多少个分组
		@Override
		public int getGroupCount() {
			// return CommonNumDao.getGroupCount();
			groupNames = CommonNumDao.getGroupInfos();
			return groupNames.size();
		}

		@Override
		public int getChildrenCount(int groupPosition) {// 0 開始
			List<String> childreninfos;
			if (childrenCacheInfos.containsKey(groupPosition)) {
				childreninfos = childrenCacheInfos.get(groupPosition);
			} else {
				childreninfos = CommonNumDao
						.getChildrenInfosByPosition(groupPosition);
				childrenCacheInfos.put(groupPosition, childreninfos);
			}
			return childreninfos.size();
		}

		@Override
		public Object getGroup(int groupPosition) {
			return null;
		}

		@Override
		public Object getChild(int groupPosition, int childPosition) {
			return null;
		}

		@Override
		public long getGroupId(int groupPosition) {
			return 0;
		}

		@Override
		public long getChildId(int groupPosition, int childPosition) {
			return 0;
		}

		@Override
		public boolean hasStableIds() {
			return false;
		}

		@Override
		public View getGroupView(int groupPosition, boolean isExpanded,
				View convertView, ViewGroup parent) {
			TextView tv;
			if(convertView!=null&&convertView instanceof TextView){
				tv = (TextView) convertView;
			}else{
				tv = new TextView(getApplicationContext());
			}

			tv.setTextSize(25);
			tv.setTextColor(Color.RED);
			// tv.setText("      "+CommonNumDao.getGroupName(groupPosition));
			tv.setText("      " + groupNames.get(groupPosition));
			return tv;
		}

		@Override
		public View getChildView(int groupPosition, int childPosition,
				boolean isLastChild, View convertView, ViewGroup parent) {
			TextView tv;
			if(convertView!=null&&convertView instanceof TextView){
				tv = (TextView) convertView;
			}else{
				tv = new TextView(getApplicationContext());
			}
			tv.setTextSize(18);
			tv.setTextColor(Color.BLUE);
//			tv.setText(CommonNumDao.getChildInfoByPosition(groupPosition,
//					childPosition));
			tv.setText(childrenCacheInfos.get(groupPosition).get(childPosition));
			return tv;
		}

		@Override
		public boolean isChildSelectable(int groupPosition, int childPosition) {
			return true;
		}

	}
}

7、BaseAdapter数据适配器的还有一种使用方法demo:

package com.example.yqqmobilesafe;

import com.example.yqqmobilesafe.cleanache.CleanCacheActivity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class OftenUseFunctionActivity extends Activity {
	private boolean D=true;
	 private GridView mGridView;//经常使用功能显示
	 private GVAdapter mAdapter;

	 private String[] items={"清理加速","话费流量","骚扰拦截","防吸费","支付保镖","手机杀毒"};
	 private int[] icons={R.drawable.exam_frequently_used_tools_icon_clean,R.drawable.exam_frequently_used_tools_icon_net_traffic,R.drawable.exam_frequently_used_tools_icon_block_anoy,R.drawable.exam_frequently_used_tools_icon_costguard,R.drawable.exam_frequently_used_tools_icon_guardpay,R.drawable.exam_frequently_used_tools_icon_malware};
	public OftenUseFunctionActivity() {
		// TODO Auto-generated constructor stub
	}
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_tab_often_use_function);
		//数据适配
		mGridView=(GridView)this.findViewById(R.id.gv_home);
		mAdapter=new GVAdapter();
		mGridView.setAdapter(mAdapter);

		setListener();
	}

	  private void setListener() {
		  mGridView.setOnItemClickListener(new OnItemClickListener() {

			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				switch (position) {
				case 0:
					Intent intent=new Intent(OftenUseFunctionActivity.this,CleanCacheActivity.class);
					startActivity(intent);
					if(D){
					Log.i("OftenUseFunctionActivity","清理加速");
					}
					break;
				case 1:
					if(D){
						Log.i("OftenUseFunctionActivity","话费流量");
						}
					break;
				case 2:
					if(D){
						Log.i("OftenUseFunctionActivity","骚扰拦截");

						}
					Intent intent2=new Intent(OftenUseFunctionActivity.this,StopAnonyActivity.class);
					startActivity(intent2);
					break;
				case 3:
					if(D){
						Log.i("OftenUseFunctionActivity","防吸费");
						}
					break;
				case 4:
					if(D){
						Log.i("OftenUseFunctionActivity","支付保镖");
						}
					break;
				case 5:
					Intent intent6=new Intent(OftenUseFunctionActivity.this,KillVirusActivity.class);
					startActivity(intent6);

					if(D){
						Log.i("OftenUseFunctionActivity","手机杀毒");
						}
					break;

				}

			}

		});

	}

	//採用功能的数据适配器
    private class GVAdapter extends BaseAdapter{

		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return items.length;
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return null;
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {

				View view=View.inflate(OftenUseFunctionActivity.this,R.layout.home_item,null);
				ImageView ivIcon=(ImageView) view.findViewById(R.id.iv_home_icon);
				TextView tvFunName=(TextView) view.findViewById(R.id.tv_home_function_name);

				ivIcon.setImageResource(icons[position]);
				tvFunName.setText(items[position]);

			return view;
		}

    }

    static class ViewHolder{
    	ImageView ivIcon;//功能图标
    	TextView tvFunName;//功能描写叙述

    }

}

home_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="95dp"
    android:gravity="center"
    android:background="@drawable/grid_selector" >

    <ImageView
        android:layout_marginTop="5dp"
        android:id="@+id/iv_home_icon"
        android:layout_width="55dp"
        android:layout_height="45dp"
       />

    <TextView
        android:layout_marginTop="5dp"
        android:id="@+id/tv_home_function_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginRight="10dp"
        android:gravity="center_vertical"

        android:textColor="#000000"
        android:textSize="20sp" />
</LinearLayout>

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