Android实战简易教程-第五十四枪（通过实现OnScrollListener接口实现下拉刷新功能）

上一篇文章Android实战简易教程-第五十三枪（通过实现OnScrollListener接口实现上拉加载更多功能）讲述了如何实现上拉加载更多的功能，本篇，我们在上一篇的基础上实现下拉刷新功能。主要通过对滚动状态和手势监听实现这一功能，下面我们看一下代码：
1.header.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="wrap_content"
    android:orientation="vertical" >

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="10dip"
        android:paddingTop="10dip" >

        <LinearLayout
            android:id="@+id/layout"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:gravity="center"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/tip"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="下拉可以刷新！" />

            <TextView
                android:id="@+id/lastupdate_time"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>

        <ImageView
            android:id="@+id/arrow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toLeftOf="@id/layout"
            android:layout_marginRight="20dip"
            android:src="@drawable/pull_to_refresh_arrow" />

        <ProgressBar
            android:id="@+id/progress"
            style="?android:attr/progressBarStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toLeftOf="@id/layout"
            android:layout_marginRight="20dip"
            android:visibility="gone" />
    </RelativeLayout>

</LinearLayout>

2.LoadListView.java:

package com.example.listviewscrolldemo;

import java.text.SimpleDateFormat;
import java.util.Date;

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.ViewGroup;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class LoadListView extends ListView implements OnScrollListener {
	private int lastVisibleItem;// 最后一个可见项
	private int totalItems;// 所有项
	private int firstVisibleItem;// 第一可见项
	private View footer, header;// 底部布局
	private Boolean isLoading = false;
	private Boolean isRemark = false;// 判断在当前页面的最顶端并下滑；
	private int startY;// Y坐标值
	private ILoadListener iListener;
	private RLoadListener rListener;
	private int scrollState;// 当前滚动状态；全局变量
	private int headerHeight;// 顶部布局文件的高度；

	final int NONE = 0;// 正常状态；
	final int PULL = 1;// 提示下拉状态；
	final int RELESE = 2;// 提示释放状态；
	final int REFLASHING = 3;// 刷新状态；

	private int state;// 判断当前状态

	public LoadListView(Context context) {
		super(context);
		initView(context);
	}

	public LoadListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		initView(context);
	}

	public LoadListView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		initView(context);
	}

	/**
	 * 添加底部加载提示到布局Listview
	 * 
	 * @param context
	 */
	private void initView(Context context) {
		LayoutInflater inflater = LayoutInflater.from(context);
		footer = inflater.inflate(R.layout.footer, null);
		header = inflater.inflate(R.layout.header_layout, null);
		footer.findViewById(R.id.ll_footer).setVisibility(View.GONE);// 首先设置加载提示不可见
		measureView(header);
		headerHeight = header.getMeasuredHeight();
		Log.i("tag", "headerHeight = " + headerHeight);
		topPadding(-headerHeight);
		this.addFooterView(footer);
		this.addHeaderView(header);
		this.setOnScrollListener(this);// 设置滚动监听

	}

	/**
	 * 通知父布局，占用的宽，高；
	 * 
	 * @param view
	 */
	private void measureView(View view) {
		ViewGroup.LayoutParams p = view.getLayoutParams();
		if (p == null) {
			p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
		}
		int width = ViewGroup.getChildMeasureSpec(0, 0, p.width);
		int height;
		int tempHeight = p.height;
		if (tempHeight > 0) {
			height = MeasureSpec.makeMeasureSpec(tempHeight, MeasureSpec.EXACTLY);
		} else {
			height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
		}
		view.measure(width, height);
	}

	/**
	 * 设置header 布局 上边距；
	 * 
	 * @param topPadding
	 */
	private void topPadding(int topPadding) {
		header.setPadding(header.getPaddingLeft(), topPadding, header.getPaddingRight(), header.getPaddingBottom());
		header.invalidate();
	}

	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		this.scrollState = scrollState;
		if (lastVisibleItem == totalItems && scrollState == SCROLL_STATE_IDLE) {

			if (!isLoading) {// 判断不是正在加载！
				footer.findViewById(R.id.ll_footer).setVisibility(View.VISIBLE);// 首先设置加载提示可见
				iListener.onLoad();
				isLoading = true;
			}

		}

	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
		this.lastVisibleItem = firstVisibleItem + visibleItemCount;
		this.totalItems = totalItemCount;
		this.firstVisibleItem = firstVisibleItem;
	}

	// 传递
	public void setInterface(ILoadListener iListener) {
		this.iListener = iListener;
	}

	public void setRefreshInterface(RLoadListener rListener) {
		this.rListener = rListener;
	}

	/**
	 * 加载更多数据的回调接口
	 * 
	 * @author Administrator
	 *
	 */
	public interface ILoadListener {
		public void onLoad();
	}

	/**
	 * 下拉刷新回调接口
	 * 
	 * @author Administrator
	 *
	 */
	public interface RLoadListener {
		public void onRefresh();
	}

	// 加载完毕
	public void loadCompleted() {
		isLoading = false;
		footer.findViewById(R.id.ll_footer).setVisibility(View.GONE);
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		// TODO Auto-generated method stub
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN://下拉
			if (firstVisibleItem == 0) {
				isRemark = true;
				startY = (int) ev.getY();
			}
			break;

		case MotionEvent.ACTION_MOVE://移动
			onMove(ev);
			break;
		case MotionEvent.ACTION_UP://上拉
			if (state == RELESE) {
				state = REFLASHING;
				// 加载最新数据；
				reflashViewByState();
				rListener.onRefresh();
			} else if (state == PULL) {
				state = NONE;
				isRemark = false;
				reflashViewByState();
			}
			break;
		}
		return super.onTouchEvent(ev);
	}

	/**
	 * 判断移动过程操作；
	 * 
	 * @param ev
	 */
	private void onMove(MotionEvent ev) {
		if (!isRemark) {
			return;
		}
		int tempY = (int) ev.getY();
		int space = tempY - startY;
		int topPadding = space - headerHeight;
		switch (state) {
		case NONE:
			if (space > 0) {// 向下滑动
				state = PULL;
				reflashViewByState();
			}
			break;
		case PULL:
			topPadding(topPadding);
			if (space > headerHeight + 30 && scrollState == SCROLL_STATE_TOUCH_SCROLL) {// 如果正在滚动切超过30
				state = RELESE;
				reflashViewByState();
			}
			break;
		case RELESE:
			topPadding(topPadding);
			if (space < headerHeight + 30) {
				state = PULL;
				reflashViewByState();
			} else if (space <= 0) {
				state = NONE;
				isRemark = false;
				reflashViewByState();
			}
			break;
		}
	}

	/**
	 * 根据当前状态，改变界面显示；
	 */
	private void reflashViewByState() {
		TextView tip = (TextView) header.findViewById(R.id.tip);
		ImageView arrow = (ImageView) header.findViewById(R.id.arrow);
		ProgressBar progress = (ProgressBar) header.findViewById(R.id.progress);
		RotateAnimation anim = new RotateAnimation(0, 180, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim.setDuration(500);
		anim.setFillAfter(true);
		RotateAnimation anim1 = new RotateAnimation(180, 0, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim1.setDuration(500);
		anim1.setFillAfter(true);
		/**
		 * 四种状态
		 */
		switch (state) {
		case NONE:
			arrow.clearAnimation();
			topPadding(-headerHeight);
			break;

		case PULL:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("下拉可以刷新！");
			arrow.clearAnimation();
			arrow.setAnimation(anim1);
			break;
		case RELESE:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("松开可以刷新！");
			arrow.clearAnimation();
			arrow.setAnimation(anim);
			break;
		case REFLASHING:
			topPadding(50);
			arrow.setVisibility(View.GONE);
			progress.setVisibility(View.VISIBLE);
			tip.setText("正在刷新...");
			arrow.clearAnimation();
			break;
		}
	}

	/**
	 * 获取完数据；
	 */
	public void reflashComplete() {
		state = NONE;
		isRemark = false;
		reflashViewByState();
		TextView lastupdatetime = (TextView) header.findViewById(R.id.lastupdate_time);
		SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
		Date date = new Date(System.currentTimeMillis());
		String time = format.format(date);
		lastupdatetime.setText(time);
	}
}

这里我们定义了四种状态：
final int NONE = 0;// 正常状态；
final int PULL = 1;// 提示下拉状态；（下拉距离比较短，此时松开不刷新）
final int RELESE = 2;// 提示释放状态；（下拉距离较长，此时松开刷新）
final int REFLASHING = 3;// 刷新状态；（松开状态，正在刷新）

这四种状态决定了header布局的不同展示效果，具体由reflashViewByState()方法实现。
onMove()方法通过判断移动过程，实现四种状态之间的转换。

package com.example.listviewscrolldemo;

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

import com.example.listviewscrolldemo.LoadListView.ILoadListener;
import com.example.listviewscrolldemo.LoadListView.RLoadListener;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.ArrayAdapter;

public class MainActivity extends Activity implements ILoadListener, RLoadListener {
	private LoadListView mListView;
	private ArrayAdapter<String> adapter;
	private List<String> datas;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initViews();
		initDatas();
	}

	private void initDatas() {
		for (int i = 1; i < 21; i++) {
			datas.add("数据" + i + "");
		}

	}

	private void initMoreDatas() {
		for (int i = 1; i < 3; i++) {
			datas.add("新数据" + i + "");
		}

	}

	private void initViews() {
		mListView = (LoadListView) findViewById(R.id.lv_main);
		mListView.setInterface(this);
		mListView.setRefreshInterface(this);
		datas = new ArrayList<String>();
		adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, datas);
		// adapter=new
		// ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1);
		mListView.setAdapter(adapter);
	}

	@Override
	public void onLoad() {
		// 添加延时效果
		Handler handler = new Handler();
		handler.postDelayed(new Runnable() {
			public void run() {

				initMoreDatas();// 获取更多数据
				adapter.notifyDataSetChanged();// 刷新ListView
				mListView.loadCompleted();// 隐藏加载提示
			}
		}, 2000);

	}

	@Override
	public void onRefresh() {
		// 添加延时效果
		Handler handler = new Handler();
		handler.postDelayed(new Runnable() {
			public void run() {

				initRefreshDatas();// 获取更多数据
				adapter.notifyDataSetChanged();// 刷新ListView
				mListView.reflashComplete();// 隐藏刷新提示
			}

		}, 2000);
	}

	private void initRefreshDatas() {
		// datas.add("新数据" + i + "");
		datas.add(0, "下拉刷新数据" + 1 + "");//此方法插入表头
		datas.add(0, "下拉刷新数据" + 2 + "");
	}

}

运行本实例如下：



届时，上拉加载和下拉刷新功能都实现了。
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