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();}@Overridepublic 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;}}}@Overridepublic 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);}@Overridepublic boolean onTouchEvent(MotionEvent ev) {// TODO Auto-generated method stubswitch (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30state = 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;@Overrideprotected 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);}@Overridepublic 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ListViewmListView.loadCompleted();// 隐藏加载提示}}, 2000);}@Overridepublic 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ListViewmListView.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。

喜欢的朋友关注我吧！谢谢

源码下载