Android的ListView是应用最广的一个组件,功能强大,扩展性灵活(不局限于ListView本身一个类),前面的文章有介绍分组,拖拽,3D立体,游标,圆角,而今天我们要介绍的是另外一个扩展ListView:下拉刷新的ListView。
4. HeaderView的默认高度测量
因为下拉到HeaderView全部显示出来,就由提示"下拉刷新"变为"松手刷新",全部显示的出来的测量标准就是header.getBottom()>=header的高度。
所以,首先我们需要测量HeaderView的默认高度。
5. scrollState监听记录
scrollState有3种,使用onScrollStateChanged()方法监听记录。
6. 刷新状态分析
因为一些地方需要知道我们处在正常状态下还是进入下拉刷新状态还是松手反弹状态,比如,
(1). 在非正常的状态下,我们不小心飞滑了一下(松手的瞬间容易出现这种情况),我们不能setSelection(1)的,否则总是松手后header跳的一下消失掉了。
(2). 下拉后要做一个下拉效果的特殊处理,需要用到OVER_PULL_REFRESH(松手刷新状态下)
(3). 松手反弹后要做一个反弹效果的特殊处理,需要用到OVER_PULL_REFRESH和ENTER_PULL_REFRESH。
6. 下拉效果的特殊处理
所谓的特殊处理,当header完全显示后,下拉只按下拉1/3的距离下拉,给用户一种艰难下拉,该松手的弹簧感觉。
这个在onTouchEvent里处理比较方便:
7. 反弹效果的特殊处理
松手后我们需要一个柔性的反弹效果,意味着我们弹回去的过程需要分一步步走,我的解决方案是:
在子线程里计算PaddingTop,并减少到原来的3/4,循环通知主线程,直到PaddingTop小于1(这个值取一个小值,合适即可)。
松手后,当然是在onTouchEvent的ACTION_UP条件下处理比较方便:
8. 切入数据加载过程
上面数据后台处理我们用sleep(2000)来处理,实际处理中,作为公共组件,我们也不好把具体代码直接写在这里,我们需要一个更灵活的分离:
(1). 定义接口
(2). 注入接口
9. 扩展"更多"功能
下拉刷新之外,我们也可以通过相同方法使用FooterView切入底部"更多"过程,这里我就不详细说明了
10. 源码
上面的每段代码都看做是"零部件",需要组合一下。
因为我们上面实现了下拉刷新,还增加了"更多"功能,我们直接命名这个类为RefreshListView吧:
package com.tianxia.lib.baseworld.widget;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.tianxia.lib.baseworld.R;
/**
* 下拉刷新,底部更多
*
*/
public class RefreshListView extends ListView implements OnScrollListener{
private float mDownY;
private float mMoveY;
private int mHeaderHeight;
private int mCurrentScrollState;
private final static int NONE_PULL_REFRESH = 0; //正常状态
private final static int ENTER_PULL_REFRESH = 1; //进入下拉刷新状态
private final static int OVER_PULL_REFRESH = 2; //进入松手刷新状态
private final static int EXIT_PULL_REFRESH = 3; //松手后反弹和加载状态
private int mPullRefreshState = 0; //记录刷新状态
private final static int REFRESH_BACKING = 0; //反弹中
private final static int REFRESH_BACED = 1; //达到刷新界限,反弹结束后
private final static int REFRESH_RETURN = 2; //没有达到刷新界限,返回
private final static int REFRESH_DONE = 3; //加载数据结束
private LinearLayout mHeaderLinearLayout = null;
private LinearLayout mFooterLinearLayout = null;
private TextView mHeaderTextView = null;
private TextView mHeaderUpdateText = null;
private ImageView mHeaderPullDownImageView = null;
private ImageView mHeaderReleaseDownImageView = null;
private ProgressBar mHeaderProgressBar = null;
private TextView mFooterTextView = null;
private ProgressBar mFooterProgressBar = null;
private SimpleDateFormat mSimpleDateFormat;
private Object mRefreshObject = null;
private RefreshListener mRefreshListener = null;
public void setOnRefreshListener(RefreshListener refreshListener) {
this.mRefreshListener = refreshListener;
}
public RefreshListView(Context context) {
this(context, null);
}
public RefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
void init(final Context context) {
mHeaderLinearLayout = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.refresh_list_header, null);
addHeaderView(mHeaderLinearLayout);
mHeaderTextView = (TextView) findViewById(R.id.refresh_list_header_text);
mHeaderUpdateText = (TextView) findViewById(R.id.refresh_list_header_last_update);
mHeaderPullDownImageView = (ImageView) findViewById(R.id.refresh_list_header_pull_down);
mHeaderReleaseDownImageView = (ImageView) findViewById(R.id.refresh_list_header_release_up);
mHeaderProgressBar = (ProgressBar) findViewById(R.id.refresh_list_header_progressbar);
mFooterLinearLayout = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.refresh_list_footer, null);
addFooterView(mFooterLinearLayout);
mFooterProgressBar = (ProgressBar) findViewById(R.id.refresh_list_footer_progressbar);
mFooterTextView = (TextView) mFooterLinearLayout.findViewById(R.id.refresh_list_footer_text);
mFooterLinearLayout.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (context.getString(R.string.app_list_footer_more).equals(mFooterTextView.getText())) {
mFooterTextView.setText(R.string.app_list_footer_loading);
mFooterProgressBar.setVisibility(View.VISIBLE);
if (mRefreshListener != null) {
mRefreshListener.more();
}
}
}
});
setSelection(1);
setOnScrollListener(this);
measureView(mHeaderLinearLayout);
mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
mSimpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm");
mHeaderUpdateText.setText(context.getString(R.string.app_list_header_refresh_last_update, mSimpleDateFormat.format(new Date())));
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
mDownY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
mMoveY = ev.getY();
if (mPullRefreshState == OVER_PULL_REFRESH) {
mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
(int)((mMoveY - mDownY)/3),
mHeaderLinearLayout.getPaddingRight(),
mHeaderLinearLayout.getPaddingBottom());
}
break;
case MotionEvent.ACTION_UP:
//when you action up, it will do these:
//1. roll back util header topPadding is 0
//2. hide the header by setSelection(1)
if (mPullRefreshState == OVER_PULL_REFRESH || mPullRefreshState == ENTER_PULL_REFRESH) {
new Thread() {
public void run() {
Message msg;
while(mHeaderLinearLayout.getPaddingTop() > 1) {
msg = mHandler.obtainMessage();
msg.what = REFRESH_BACKING;
mHandler.sendMessage(msg);
try {
sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
msg = mHandler.obtainMessage();
if (mPullRefreshState == OVER_PULL_REFRESH) {
msg.what = REFRESH_BACED;
} else {
msg.what = REFRESH_RETURN;
}
mHandler.sendMessage(msg);
};
}.start();
}
break;
}
return super.onTouchEvent(ev);
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
&& firstVisibleItem == 0
&& (mHeaderLinearLayout.getBottom() >= 0 && mHeaderLinearLayout.getBottom() < mHeaderHeight)) {
//进入且仅进入下拉刷新状态
if (mPullRefreshState == NONE_PULL_REFRESH) {
mPullRefreshState = ENTER_PULL_REFRESH;
}
} else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
&& firstVisibleItem == 0
&& (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
//下拉达到界限,进入松手刷新状态
if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
mPullRefreshState = OVER_PULL_REFRESH;
mDownY = mMoveY; //为下拉1/3折扣效果记录开始位置
mHeaderTextView.setText("松手刷新");//显示松手刷新
mHeaderPullDownImageView.setVisibility(View.GONE);//隐藏"下拉刷新"
mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);//显示向上的箭头
}
} else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL && firstVisibleItem != 0) {
//不刷新了
if (mPullRefreshState == ENTER_PULL_REFRESH) {
mPullRefreshState = NONE_PULL_REFRESH;
}
} else if (mCurrentScrollState == SCROLL_STATE_FLING && firstVisibleItem == 0) {
//飞滑状态,不能显示出header,也不能影响正常的飞滑
//只在正常情况下才纠正位置
if (mPullRefreshState == NONE_PULL_REFRESH) {
setSelection(1);
}
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
mCurrentScrollState = scrollState;
}
@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);
setSelection(1);
}
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);
}
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case REFRESH_BACKING:
mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
(int) (mHeaderLinearLayout.getPaddingTop()*0.75f),
mHeaderLinearLayout.getPaddingRight(),
mHeaderLinearLayout.getPaddingBottom());
break;
case REFRESH_BACED:
mHeaderTextView.setText("正在加载...");
mHeaderProgressBar.setVisibility(View.VISIBLE);
mHeaderPullDownImageView.setVisibility(View.GONE);
mHeaderReleaseDownImageView.setVisibility(View.GONE);
mPullRefreshState = EXIT_PULL_REFRESH;
new Thread() {
public void run() {
if (mRefreshListener != null) {
mRefreshObject = mRefreshListener.refreshing();
}
Message msg = mHandler.obtainMessage();
msg.what = REFRESH_DONE;
mHandler.sendMessage(msg);
};
}.start();
break;
case REFRESH_RETURN:
mHeaderTextView.setText("下拉刷新");
mHeaderProgressBar.setVisibility(View.INVISIBLE);
mHeaderPullDownImageView.setVisibility(View.VISIBLE);
mHeaderReleaseDownImageView.setVisibility(View.GONE);
mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
0,
mHeaderLinearLayout.getPaddingRight(),
mHeaderLinearLayout.getPaddingBottom());
mPullRefreshState = NONE_PULL_REFRESH;
setSelection(1);
break;
case REFRESH_DONE:
mHeaderTextView.setText("下拉刷新");
mHeaderProgressBar.setVisibility(View.INVISIBLE);
mHeaderPullDownImageView.setVisibility(View.VISIBLE);
mHeaderReleaseDownImageView.setVisibility(View.GONE);
mHeaderUpdateText.setText(getContext().getString(R.string.app_list_header_refresh_last_update,
mSimpleDateFormat.format(new Date())));
mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
0,
mHeaderLinearLayout.getPaddingRight(),
mHeaderLinearLayout.getPaddingBottom());
mPullRefreshState = NONE_PULL_REFRESH;
setSelection(1);
if (mRefreshListener != null) {
mRefreshListener.refreshed(mRefreshObject);
}
break;
default:
break;
&nb
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