Android ListView下拉刷新
2012-11-17 17:15
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下拉刷新原理：
重新ListView，addHeaderView（），增加一个头部信息“松开刷新...”类似字样；
在OnTouchEvent监听事件中，当触发ACTION_MOVE时，设置headerView的距上的内边距paddingTop；
当向下拖动，满足一定条件时，头部视图执行动画、更新文字等处理；
添加一个OnRefreshListener接口，定义一个回调函数onRefresh（），在回调方法中添加异步操作处理；
共需要四个文件：PullToRefreshActivity，PullToRefreshListView，pull_to_refresh_header.xml，pull_to_refreshListView.xml。
PullToRefreshActivity：
package com.markupartist.android.example.pulltorefresh;
import java.util.Arrays;
import java.util.LinkedList;
import android.app.Activity;
import android.app.ListActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import com.markupartist.android.widget.PullToRefreshListView;
import com.markupartist.android.widget.PullToRefreshListView.OnRefreshListener;
public class PullToRefreshActivity extends Activity {
private LinkedList<String> mListItems;
private PullToRefreshListView mlistview;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.pull_to_refresh);
// Set a listener to be invoked when the list should be refreshed.
mlistview = ((PullToRefreshListView)PullToRefreshActivity.this.findViewById(R.id.usalist) );
mlistview.setOnRefreshListener(new OnRefreshListener() {
@Override
public void onRefresh() {
// TODO Auto-generated method stub
new GetDataTask().execute();
}
});
mListItems = new LinkedList<String>();
mListItems.addAll(Arrays.asList(mStrings));
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, mListItems);
mlistview.setAdapter(adapter);
}
private class GetDataTask extends AsyncTask<Void, Void, String[]> {
@Override
protected String[] doInBackground(Void... params) {
// Simulates a background job.
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
;
}
return mStrings;
}
@Override
protected void onPostExecute(String[] result) {
mListItems.addFirst("Added after refresh...");
// Call onRefreshComplete when the list has been refreshed.
mlistview.onRefreshComplete();
super.onPostExecute(result);
}
}
private String[] mStrings = {
"Abbaye de Belloc", "Abbaye du Mont des Cats", "Abertam",
"Abondance", "Ackawi", "Acorn", "Adelost", "Affidelice au Chablis",
"Afuega'l Pitu", "Airag", "Airedale", "Aisy Cendre",
"Allgauer Emmentaler"};
}PullToRefreshListView：
package com.markupartist.android.widget;
import com.markupartist.android.example.pulltorefresh.R;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;
public class PullToRefreshListView extends ListView implements OnScrollListener {
// 状态
private static final int TAP_TO_REFRESH = 1;//点击刷新
private static final int PULL_TO_REFRESH = 2; //拉动刷新
private static final int RELEASE_TO_REFRESH = 3; //释放刷新
private static final int REFRESHING = 4; //正在刷新
// 当前滑动状态
private int mCurrentScrollState;
// 当前刷新状态
private int mRefreshState;
//头视图的高度
private int mRefreshViewHeight;
//头视图 原始的top padding 属性值
private int mRefreshOriginalTopPadding;
private int mLastMotionY;
// 监听对listview的滑动动作
private OnRefreshListener mOnRefreshListener;
//箭头图片
private static int REFRESHICON = R.drawable.goicon;
//listview 滚动监听器
private OnScrollListener mOnScrollListener;
private LayoutInflater mInflater;
private RelativeLayout mRefreshView;
//顶部刷新时出现的控件
private TextView mRefreshViewText;
private ImageView mRefreshViewImage;
private ProgressBar mRefreshViewProgress;
private TextView mRefreshViewLastUpdated;
// 箭头动画效果
//变为向下的箭头
private RotateAnimation mFlipAnimation;
//变为逆向的箭头
private RotateAnimation mReverseFlipAnimation;
//是否反弹
private boolean mBounceHack;
public PullToRefreshListView(Context context) {
super(context);
init(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
/**
* 初始化控件和箭头动画（这里直接在代码中初始化动画而不是通过xml）
*/
private void init(Context context) {
// Load all of the animations we need in code rather than through XML
//第一个参数fromDegrees为动画起始时的旋转角度
//第二个参数toDegrees为动画旋转到的角度
//第三个参数pivotXType为动画在X轴相对于物件位置类型
//第四个参数pivotXValue为动画相对于物件的X坐标的开始位置
//第五个参数pivotXType为动画在Y轴相对于物件位置类型
//第六个参数pivotYValue为动画相对于物件的Y坐标的开始位置
mFlipAnimation = new RotateAnimation(0, -180,RotateAnimation.RELATIVE_TO_SELF,
0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mFlipAnimation.setInterpolator(new LinearInterpolator());
mFlipAnimation.setDuration(250);
mFlipAnimation.setFillAfter(true);
mReverseFlipAnimation = new RotateAnimation(-180, 0,RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mReverseFlipAnimation.setInterpolator(new LinearInterpolator());
mReverseFlipAnimation.setDuration(250);
mReverseFlipAnimation.setFillAfter(true);
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mRefreshView = (RelativeLayout) mInflater.inflate(R.layout.pull_to_refresh_header, this, false);
mRefreshViewText =(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_text);
mRefreshViewImage =(ImageView) mRefreshView.findViewById(R.id.pull_to_refresh_image);
mRefreshViewProgress =(ProgressBar) mRefreshView.findViewById(R.id.pull_to_refresh_progress);
mRefreshViewLastUpdated =(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);
mRefreshViewImage.setMinimumHeight(50);
mRefreshView.setOnClickListener(new OnClickRefreshListener());
mRefreshOriginalTopPadding = mRefreshView.getPaddingTop();
mRefreshState = TAP_TO_REFRESH;
//为listview头部增加一个view
addHeaderView(mRefreshView);
super.setOnScrollListener(this);
measureView(mRefreshView);
mRefreshViewHeight = mRefreshView.getMeasuredHeight();
}
@Override
protected void onAttachedToWindow() {
setSelection(1);
}
@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);
setSelection(1);
}
/**
* Set the listener that will receive notifications every time the list scrolls.
* @param l The scroll listener.
*/
@Override
public void setOnScrollListener(AbsListView.OnScrollListener l) {
mOnScrollListener = l;
}
/**
* Register a callback to be invoked when this list should be refreshed.
* @param onRefreshListener The callback to run.
*/
public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
mOnRefreshListener = onRefreshListener;
}
/**
* Set a text to represent when the list was last updated.
* @param lastUpdated Last updated at.
*/
public void setLastUpdated(CharSequence lastUpdated) {
if (lastUpdated != null) {
mRefreshViewLastUpdated.setVisibility(View.VISIBLE);
mRefreshViewLastUpdated.setText(lastUpdated);
} else {
mRefreshViewLastUpdated.setVisibility(View.GONE);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
//当前手指的Y值
final int y = (int) event.getY();
mBounceHack = false;
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
//将垂直滚动条设置为可用状态
if (!isVerticalScrollBarEnabled()) {
setVerticalScrollBarEnabled(true);
}
if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {
// 拖动距离达到刷新需要
if ((mRefreshView.getBottom() >= mRefreshViewHeight
|| mRefreshView.getTop() >= 0)
&& mRefreshState == RELEASE_TO_REFRESH) {
// 把状态设置为正在刷新
// Initiate the refresh
mRefreshState = REFRESHING; //将标量设置为，正在刷新
// 准备刷新
prepareForRefresh();
// 刷新
onRefresh();
} else if (mRefreshView.getBottom() < mRefreshViewHeight
|| mRefreshView.getTop() <= 0) {
// Abort refresh and scroll down below the refresh view
//停止刷新，并且滚动到头部刷新视图的下一个视图
resetHeader();
setSelection(1); //定位在第二个列表项
}
}
break;
case MotionEvent.ACTION_DOWN:
// 获得按下y轴位置
mLastMotionY = y;
break;
case MotionEvent.ACTION_MOVE:
//更行头视图的toppadding 属性
applyHeaderPadding(event);
break;
}
return super.onTouchEvent(event);
}
// 获得header距离
private void applyHeaderPadding(MotionEvent ev) {
//获取累积的动作数
int pointerCount = ev.getHistorySize();
for (int p = 0; p < pointerCount; p++) {
//如果是释放将要刷新状态
if (mRefreshState == RELEASE_TO_REFRESH) {
if (isVerticalFadingEdgeEnabled()) {
setVerticalScrollBarEnabled(false);
}
//历史累积的高度
int historicalY = (int) ev.getHistoricalY(p);
// Calculate the padding to apply, we divide by 1.7 to
// simulate a more resistant effect during pull.
// 计算申请的边距，除以1.7使得拉动效果更好
int topPadding = (int) (((historicalY - mLastMotionY)- mRefreshViewHeight) / 1.7);
mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
topPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}
}
}
/**
* Sets the header padding back to original size.
* 将head的边距重置为初始的数值
*/
private void resetHeaderPadding() {
mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
mRefreshOriginalTopPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}
/**
* Resets the header to the original state.
* 重置header为之前的状态
*/
private void resetHeader() {
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshState = TAP_TO_REFRESH;
resetHeaderPadding();
// 将刷新图标换成箭头
// Set refresh view text to the pull label
mRefreshViewText.setText(R.string.pull_to_refresh_tap_label);
// Replace refresh drawable with arrow drawable
// 清除动画
mRefreshViewImage.setImageResource(REFRESHICON);
// Clear the full rotation animation
mRefreshViewImage.clearAnimation();
// Hide progress bar and arrow.
// 隐藏图标和进度条
mRefreshViewImage.setVisibility(View.GONE);
mRefreshViewProgress.setVisibility(View.GONE);
}
}
//测量视图的高度
private void measureView(View child) {
ViewGroup.LayoutParams p = child.getLayoutParams();
if (p == null) {
p = new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
int childWidthSpec = ViewGroup.getChildMeasureSpec(0,0 + 0, p.width);
int lpHeight = p.height;
int childHeightSpec;
if (lpHeight > 0) {
childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);
} else {
childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
child.measure(childWidthSpec, childHeightSpec);
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount) {
// When the refresh view is completely visible, change the text to say
// "Release to refresh..." and flip the arrow drawable.
// 在refreshview完全可见时，设置文字为松开刷新，同时翻转箭头
//如果是接触滚动状态,并且不是正在刷新的状态
if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL&& mRefreshState != REFRESHING) {
if (firstVisibleItem == 0) {
//如果显示出来了第一个列表项，显示刷新图片
mRefreshViewImage.setVisibility(View.VISIBLE);
//如果下拉了listiview,则显示上拉刷新动画
if ((mRefreshView.getBottom() >= mRefreshViewHeight + 20|| mRefreshView.getTop() >= 0)
&& mRefreshState != RELEASE_TO_REFRESH) {
mRefreshViewText.setText(R.string.pull_to_refresh_release_label);
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mFlipAnimation);
mRefreshState = RELEASE_TO_REFRESH;
//如果下拉距离不够，则回归原来的状态
} else if (mRefreshView.getBottom() < mRefreshViewHeight + 20
&& mRefreshState != PULL_TO_REFRESH) {
mRefreshViewText.setText(R.string.pull_to_refresh_pull_label);
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mReverseFlipAnimation);
}
mRefreshState = PULL_TO_REFRESH;
}
} else {
mRefreshViewImage.setVisibility(View.GONE);
resetHeader();
}
//如果是滚动状态+ 第一个视图已经显示+ 不是刷新状态
} else if (mCurrentScrollState == SCROLL_STATE_FLING && firstVisibleItem == 0
&& mRefreshState != REFRESHING) {
setSelection(1);
mBounceHack = true;
} else if (mBounceHack && mCurrentScrollState == SCROLL_STATE_FLING) {
setSelection(1);
}
if (mOnScrollListener != null) {
mOnScrollListener.onScroll(view, firstVisibleItem,visibleItemCount, totalItemCount);
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
mCurrentScrollState = scrollState;
if (mCurrentScrollState == SCROLL_STATE_IDLE) {
mBounceHack = false;
}
if (mOnScrollListener != null) {
mOnScrollListener.onScrollStateChanged(view, scrollState);
}
}
public void prepareForRefresh() {
resetHeaderPadding(); // 恢复header的边距
mRefreshViewImage.setVisibility(View.GONE);
// We need this hack, otherwise it will keep the previous drawable.
// 注意加上，否则仍然显示之前的图片
mRefreshViewImage.setImageDrawable(null);
mRefreshViewProgress.setVisibility(View.VISIBLE);
// Set refresh view text to the refreshing label
mRefreshViewText.setText(R.string.pull_to_refresh_refreshing_label);
mRefreshState = REFRESHING;
}
public void onRefresh() {
if (mOnRefreshListener != null) {
mOnRefreshListener.onRefresh();
}
}
/**
*
* @param lastUpdated Last updated at.
*/
/**
* Resets the list to a normal state after a refresh.
* 重置listview为普通的listview
* @param lastUpdated
* Last updated at.
*/
public void onRefreshComplete(CharSequence lastUpdated) {
setLastUpdated(lastUpdated);
onRefreshComplete();
}
/**
* Resets the list to a normal state after a refresh.
* 重置listview为普通的listview，
*/
public void onRefreshComplete() {
resetHeader();
// If refresh view is visible when loading completes, scroll down to
// the next item.
if (mRefreshView.getBottom() > 0) {
invalidateViews(); //重绘视图
setSelection(1);
}
}
/**
* Invoked when the refresh view is clicked on. This is mainly used when
* there's only a few items in the list and it's not possible to drag the
* list.
*/
private class OnClickRefreshListener implements OnClickListener {
@Override
public void onClick(View v) {
if (mRefreshState != REFRESHING) {
prepareForRefresh();
onRefresh();
}
}
}
public interface OnRefreshListener {
public void onRefresh();
}
}pull_to_refresh_header.xml：<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2011 Johan Nilsson <http://markupartist.com>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingTop="10dip"
android:paddingBottom="15dip"
android:gravity="center"
android:id="@+id/pull_to_refresh_header"
>
<ProgressBar
android:id="@+id/pull_to_refresh_progress"
android:indeterminate="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dip"
android:layout_marginRight="20dip"
android:layout_marginTop="10dip"
android:visibility="gone"
android:layout_centerVertical="true"
style="@drawable/icon"
/>
<ImageView
android:id="@+id/pull_to_refresh_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dip"
android:layout_marginRight="20dip"
android:visibility="gone"
android:layout_gravity="center"
android:gravity="center"
android:src="@drawable/goicon"
/>
<TextView
android:id="@+id/pull_to_refresh_text"
android:text="@string/pull_to_refresh_tap_label"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textStyle="bold"
android:paddingTop="5dip"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
/>
<TextView
android:id="@+id/pull_to_refresh_updated_at"
android:layout_below="@+id/pull_to_refresh_text"
android:visibility="gone"
android:textAppearance="?android:attr/textAppearanceSmall"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
/>
</RelativeLayout>pull_to_refreshListView.xml：
package com.markupartist.android.widget;
import com.markupartist.android.example.pulltorefresh.R;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;
public class PullToRefreshListView extends ListView implements OnScrollListener {
// 状态
private static final int TAP_TO_REFRESH = 1;//点击刷新
private static final int PULL_TO_REFRESH = 2; //拉动刷新
private static final int RELEASE_TO_REFRESH = 3; //释放刷新
private static final int REFRESHING = 4; //正在刷新
// 当前滑动状态
private int mCurrentScrollState;
// 当前刷新状态
private int mRefreshState;
//头视图的高度
private int mRefreshViewHeight;
//头视图 原始的top padding 属性值
private int mRefreshOriginalTopPadding;
private int mLastMotionY;
// 监听对listview的滑动动作
private OnRefreshListener mOnRefreshListener;
//箭头图片
private static int REFRESHICON = R.drawable.goicon;
//listview 滚动监听器
private OnScrollListener mOnScrollListener;
private LayoutInflater mInflater;
private RelativeLayout mRefreshView;
//顶部刷新时出现的控件
private TextView mRefreshViewText;
private ImageView mRefreshViewImage;
private ProgressBar mRefreshViewProgress;
private TextView mRefreshViewLastUpdated;
// 箭头动画效果
//变为向下的箭头
private RotateAnimation mFlipAnimation;
//变为逆向的箭头
private RotateAnimation mReverseFlipAnimation;
//是否反弹
private boolean mBounceHack;
public PullToRefreshListView(Context context) {
super(context);
init(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
/**
* 初始化控件和箭头动画（这里直接在代码中初始化动画而不是通过xml）
*/
private void init(Context context) {
// Load all of the animations we need in code rather than through XML
//第一个参数fromDegrees为动画起始时的旋转角度
//第二个参数toDegrees为动画旋转到的角度
//第三个参数pivotXType为动画在X轴相对于物件位置类型
//第四个参数pivotXValue为动画相对于物件的X坐标的开始位置
//第五个参数pivotXType为动画在Y轴相对于物件位置类型
//第六个参数pivotYValue为动画相对于物件的Y坐标的开始位置
mFlipAnimation = new RotateAnimation(0, -180,RotateAnimation.RELATIVE_TO_SELF,
0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mFlipAnimation.setInterpolator(new LinearInterpolator());
mFlipAnimation.setDuration(250);
mFlipAnimation.setFillAfter(true);
mReverseFlipAnimation = new RotateAnimation(-180, 0,RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mReverseFlipAnimation.setInterpolator(new LinearInterpolator());
mReverseFlipAnimation.setDuration(250);
mReverseFlipAnimation.setFillAfter(true);
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mRefreshView = (RelativeLayout) mInflater.inflate(R.layout.pull_to_refresh_header, this, false);
mRefreshViewText =(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_text);
mRefreshViewImage =(ImageView) mRefreshView.findViewById(R.id.pull_to_refresh_image);
mRefreshViewProgress =(ProgressBar) mRefreshView.findViewById(R.id.pull_to_refresh_progress);
mRefreshViewLastUpdated =(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);
mRefreshViewImage.setMinimumHeight(50);
mRefreshView.setOnClickListener(new OnClickRefreshListener());
mRefreshOriginalTopPadding = mRefreshView.getPaddingTop();
mRefreshState = TAP_TO_REFRESH;
//为listview头部增加一个view
addHeaderView(mRefreshView);
super.setOnScrollListener(this);
measureView(mRefreshView);
mRefreshViewHeight = mRefreshView.getMeasuredHeight();
}
@Override
protected void onAttachedToWindow() {
setSelection(1);
}
@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);
setSelection(1);
}
/**
* Set the listener that will receive notifications every time the list scrolls.
* @param l The scroll listener.
*/
@Override
public void setOnScrollListener(AbsListView.OnScrollListener l) {
mOnScrollListener = l;
}
/**
* Register a callback to be invoked when this list should be refreshed.
* @param onRefreshListener The callback to run.
*/
public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
mOnRefreshListener = onRefreshListener;
}
/**
* Set a text to represent when the list was last updated.
* @param lastUpdated Last updated at.
*/
public void setLastUpdated(CharSequence lastUpdated) {
if (lastUpdated != null) {
mRefreshViewLastUpdated.setVisibility(View.VISIBLE);
mRefreshViewLastUpdated.setText(lastUpdated);
} else {
mRefreshViewLastUpdated.setVisibility(View.GONE);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
//当前手指的Y值
final int y = (int) event.getY();
mBounceHack = false;
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
//将垂直滚动条设置为可用状态
if (!isVerticalScrollBarEnabled()) {
setVerticalScrollBarEnabled(true);
}
if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {
// 拖动距离达到刷新需要
if ((mRefreshView.getBottom() >= mRefreshViewHeight
|| mRefreshView.getTop() >= 0)
&& mRefreshState == RELEASE_TO_REFRESH) {
// 把状态设置为正在刷新
// Initiate the refresh
mRefreshState = REFRESHING; //将标量设置为，正在刷新
// 准备刷新
prepareForRefresh();
// 刷新
onRefresh();
} else if (mRefreshView.getBottom() < mRefreshViewHeight
|| mRefreshView.getTop() <= 0) {
// Abort refresh and scroll down below the refresh view
//停止刷新，并且滚动到头部刷新视图的下一个视图
resetHeader();
setSelection(1); //定位在第二个列表项
}
}
break;
case MotionEvent.ACTION_DOWN:
// 获得按下y轴位置
mLastMotionY = y;
break;
case MotionEvent.ACTION_MOVE:
//更行头视图的toppadding 属性
applyHeaderPadding(event);
break;
}
return super.onTouchEvent(event);
}
// 获得header距离
private void applyHeaderPadding(MotionEvent ev) {
//获取累积的动作数
int pointerCount = ev.getHistorySize();
for (int p = 0; p < pointerCount; p++) {
//如果是释放将要刷新状态
if (mRefreshState == RELEASE_TO_REFRESH) {
if (isVerticalFadingEdgeEnabled()) {
setVerticalScrollBarEnabled(false);
}
//历史累积的高度
int historicalY = (int) ev.getHistoricalY(p);
// Calculate the padding to apply, we divide by 1.7 to
// simulate a more resistant effect during pull.
// 计算申请的边距，除以1.7使得拉动效果更好
int topPadding = (int) (((historicalY - mLastMotionY)- mRefreshViewHeight) / 1.7);
mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
topPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}
}
}
/**
* Sets the header padding back to original size.
* 将head的边距重置为初始的数值
*/
private void resetHeaderPadding() {
mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
mRefreshOriginalTopPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}
/**
* Resets the header to the original state.
* 重置header为之前的状态
*/
private void resetHeader() {
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshState = TAP_TO_REFRESH;
resetHeaderPadding();
// 将刷新图标换成箭头
// Set refresh view text to the pull label
mRefreshViewText.setText(R.string.pull_to_refresh_tap_label);
// Replace refresh drawable with arrow drawable
// 清除动画
mRefreshViewImage.setImageResource(REFRESHICON);
// Clear the full rotation animation
mRefreshViewImage.clearAnimation();
// Hide progress bar and arrow.
// 隐藏图标和进度条
mRefreshViewImage.setVisibility(View.GONE);
mRefreshViewProgress.setVisibility(View.GONE);
}
}
//测量视图的高度
private void measureView(View child) {
ViewGroup.LayoutParams p = child.getLayoutParams();
if (p == null) {
p = new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
int childWidthSpec = ViewGroup.getChildMeasureSpec(0,0 + 0, p.width);
int lpHeight = p.height;
int childHeightSpec;
if (lpHeight > 0) {
childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);
} else {
childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
child.measure(childWidthSpec, childHeightSpec);
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount) {
// When the refresh view is completely visible, change the text to say
// "Release to refresh..." and flip the arrow drawable.
// 在refreshview完全可见时，设置文字为松开刷新，同时翻转箭头
//如果是接触滚动状态,并且不是正在刷新的状态
if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL&& mRefreshState != REFRESHING) {
if (firstVisibleItem == 0) {
//如果显示出来了第一个列表项，显示刷新图片
mRefreshViewImage.setVisibility(View.VISIBLE);
//如果下拉了listiview,则显示上拉刷新动画
if ((mRefreshView.getBottom() >= mRefreshViewHeight + 20|| mRefreshView.getTop() >= 0)
&& mRefreshState != RELEASE_TO_REFRESH) {
mRefreshViewText.setText(R.string.pull_to_refresh_release_label);
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mFlipAnimation);
mRefreshState = RELEASE_TO_REFRESH;
//如果下拉距离不够，则回归原来的状态
} else if (mRefreshView.getBottom() < mRefreshViewHeight + 20
&& mRefreshState != PULL_TO_REFRESH) {
mRefreshViewText.setText(R.string.pull_to_refresh_pull_label);
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mReverseFlipAnimation);
}
mRefreshState = PULL_TO_REFRESH;
}
} else {
mRefreshViewImage.setVisibility(View.GONE);
resetHeader();
}
//如果是滚动状态+ 第一个视图已经显示+ 不是刷新状态
} else if (mCurrentScrollState == SCROLL_STATE_FLING && firstVisibleItem == 0
&& mRefreshState != REFRESHING) {
setSelection(1);
mBounceHack = true;
} else if (mBounceHack && mCurrentScrollState == SCROLL_STATE_FLING) {
setSelection(1);
}
if (mOnScrollListener != null) {
mOnScrollListener.onScroll(view, firstVisibleItem,visibleItemCount, totalItemCount);
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
mCurrentScrollState = scrollState;
if (mCurrentScrollState == SCROLL_STATE_IDLE) {
mBounceHack = false;
}
if (mOnScrollListener != null) {
mOnScrollListener.onScrollStateChanged(view, scrollState);
}
}
public void prepareForRefresh() {
resetHeaderPadding(); // 恢复header的边距
mRefreshViewImage.setVisibility(View.GONE);
// We need this hack, otherwise it will keep the previous drawable.
// 注意加上，否则仍然显示之前的图片
mRefreshViewImage.setImageDrawable(null);
mRefreshViewProgress.setVisibility(View.VISIBLE);
// Set refresh view text to the refreshing label
mRefreshViewText.setText(R.string.pull_to_refresh_refreshing_label);
mRefreshState = REFRESHING;
}
public void onRefresh() {
if (mOnRefreshListener != null) {
mOnRefreshListener.onRefresh();
}
}
/**
*
* @param lastUpdated Last updated at.
*/
/**
* Resets the list to a normal state after a refresh.
* 重置listview为普通的listview
* @param lastUpdated
* Last updated at.
*/
public void onRefreshComplete(CharSequence lastUpdated) {
setLastUpdated(lastUpdated);
onRefreshComplete();
}
/**
* Resets the list to a normal state after a refresh.
* 重置listview为普通的listview，
*/
public void onRefreshComplete() {
resetHeader();
// If refresh view is visible when loading completes, scroll down to
// the next item.
if (mRefreshView.getBottom() > 0) {
invalidateViews(); //重绘视图
setSelection(1);
}
}
/**
* Invoked when the refresh view is clicked on. This is mainly used when
* there's only a few items in the list and it's not possible to drag the
* list.
*/
private class OnClickRefreshListener implements OnClickListener {
@Override
public void onClick(View v) {
if (mRefreshState != REFRESHING) {
prepareForRefresh();
onRefresh();
}
}
}
public interface OnRefreshListener {
public void onRefresh();
}
}
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