ListView下拉刷新

首先建立ListHeader的布局文件。用于存放下拉菜单

<?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:paddingTop="10dp"
    android:paddingBottom="10dp"
    >
    
    <FrameLayout 
        android:layout_weight="1"
        android:id="@+id/frame"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        >
        <ImageView 
            android:id="@+id/img"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:src="@drawable/ic_launcher"
            />
        <ProgressBar 
           android:id="@+id/progressbar"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            />
    </FrameLayout>


    <TextView 
        android:id="@+id/mytitle"
        android:layout_weight="2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:layout_gravity="center"
        android:text="下拉刷新"
        />
</LinearLayout>

第二步建立一个自定义的ListView对象

package com.example.myview;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class My_listview extends ListView implements OnScrollListener{
	View header;
	TextView tv;
	ImageView iv;
	ProgressBar probar;
	Animation anim_downToUp;
	Animation anim_UpToDown;
	
	int headerHigth=0;  //判断第一条被滑出的高度
	
	public My_listview(Context context, AttributeSet attrs) {
		super(context, attrs);
		
		initAnimation();//执行动画
	
		header=(View)LayoutInflater.from(context).inflate(R.layout.list_header, null);
		
		tv=(TextView)header.findViewById(R.id.mytitle);
		iv=(ImageView)header.findViewById(R.id.img);
		probar=(ProgressBar)header.findViewById(R.id.progressbar);
		
		probar.setVisibility(View.INVISIBLE); //设置滚动条初始状态为不可见
		addHeaderView(header);
     
         setSelection(1);
         
         headerHigth=getHeaderViewHeight();//获取下拉菜单的高度

		setOnScrollListener(this);
	}
           <pre name="code" class="java">          //获取下拉菜单的高度

	private int getHeaderViewHeight() {
		android.view.ViewGroup.LayoutParams params=header.getLayoutParams();
		if(params==null){
			params=new LayoutParams(android.view.ViewGroup.LayoutParams.MATCH_PARENT,android.view.ViewGroup.LayoutParams.WRAP_CONTENT);
		}
		int with=MeasureSpec.makeMeasureSpec(params.width, MeasureSpec.EXACTLY);
		int height=MeasureSpec.makeMeasureSpec(params.height, MeasureSpec.EXACTLY);
		header.measure(with, height);
		
		Log.i("==================", "                   高度"+header.getMeasuredHeight());
		return header.getMeasuredHeight();
	}
	
	
	int myscrollState;//获取滑动的方式
	boolean flag=true;//判断下滑菜单状态
	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		// TODO Auto-generated method stub
		myscrollState=scrollState;
	}
	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		// TODO Auto-generated method stub

		//判断是否是手指滑动触发的事件
		if(myscrollState==SCROLL_STATE_TOUCH_SCROLL){

			//判断是否滑动到第一条
			if(firstVisibleItem==0){

				//getBottom获取header控件的下标
				if(header.getBottom()<headerHigth){   //判断菜单是否被完全拉出

					iv.setVisibility(View.VISIBLE);
					probar.setVisibility(view.INVISIBLE);
					tv.setText("  下拉刷新......  ");
					iv.startAnimation(anim_UpToDown);
					flag=false;

				}
				else if(header.getBottom() >=headerHigth){

					iv.setVisibility(View.VISIBLE);
					probar.setVisibility(view.INVISIBLE);
					tv.setText("  释放开始刷新......  ");
					iv.startAnimation(anim_downToUp);
					flag=true;
				}
			}
		}
	}

         //设置动画效果
	private void initAnimation() {
		anim_downToUp = new RotateAnimation(0, -180,
				Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
				0.5f);
		anim_downToUp.setDuration(300);
		anim_downToUp.setFillAfter(true);

		anim_UpToDown = new RotateAnimation(-180, 0,
				Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
				0.5f);
		anim_UpToDown.setDuration(300);
		anim_UpToDown.setFillAfter(true);
	}

             //当手指抬起时的事件
	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		// TODO Auto-generated method stub
		if(ev.getAction()==MotionEvent.ACTION_UP){

                   //下拉菜单被完全拉出时 
		if(flag){
			iv.clearAnimation();//清除动画
			iv.setVisibility(View.INVISIBLE);
			probar.setVisibility(View.VISIBLE);
			tv.setText("正在刷新。。。");
			if(listener!=null){
				listener.onRefresh();
			}
		}
		else{
			iv.clearAnimation();
			setSelection(1);
		}
		}
		
		return super.onTouchEvent(ev);
		
	}

	public void refreshFinish() {
		invalidateViews();  //刷新页面，即刷新listview中所有的子Views
		iv.clearAnimation();
		setSelection(1);
		
	}


	OnRefreshListener listener;
	
	
	public void setListener(OnRefreshListener listener) {
		this.listener = listener;
	}
        //设置抽象类  用于接口回调。添加事件
	public interface OnRefreshListener{
		void onRefresh();
	}
            
	@Override
	public void setAdapter(ListAdapter adapter) {
		// TODO Auto-generated method stub
		super.setAdapter(adapter);
		setSelection(1);
	}
}

第三步在主布局文件中添加自定义ListView的控件

   <com.example.myview.My_listview 
        android:id="@+id/listview"
        android:layout_width="fill_parent"
        android:layout_height="<span style="font-family: Arial, Helvetica, sans-serif;">fill_parent</span>"
        />

第四步在主线程中设置事件

package com.example.myview;

import java.util.ArrayList;
import java.util.List;

import com.example.myview.My_listview.OnRefreshListener;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.Window;
import android.widget.ArrayAdapter;

public class MainActivity extends Activity {
	My_listview listview;
	List<String>list=new ArrayList<String>();
	ArrayAdapter< String >adapter;
	int num=0;//新添加的数据
	Handler handler = new Handler();//延迟加载数据
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.activity_main);
	    for(int i=0;i<20;i++){
       	 list.add("item"+i);
        }
        adapter=new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item,list);
        listview.setAdapter(adapter);
        listview.setListener(new OnRefreshListener() {
        	@Override
			public void onRefresh() {
				// TODO Auto-generated method stub
				Log.i("=====", "============开始下拉刷新");
				handler.postDelayed(new Runnable() {
					
					@Override
					public void run() {
						// TODO Auto-generated method stub
						num++;
						list.add(0,"新添加的数据"+num);
						//刷新页面
						listview.refreshFinish();
					}
				}, 2000);
			}
		});
	}
}

完全没有想象中的那么复杂。。。。。。。

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