android 垂直滚动字幕

package com.orgcent.demo.view; import java.lang.reflect.Field; import java.util.List; import android.content.Context; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.widget.HeaderViewListAdapter; import android.widget.ListAdapter; import android.widget.ListView; import static com.orgcent.demo.view.UpRefreshListView.OnRefreshStatusListener.*; /** * 参考了另一篇文章思路： * https://github.com/johannilsson/android-pulltorefresh * */ public class UpRefreshListView extends ListView { private OnRefreshStatusListener mStatusListener; private View mRefreshView; private TranslateHelper mTranslate; private float mLastY; private int mOldTopPadding = -1; private static int MAX_TOP_PADDING ; //init()中初始化，单位像素 private int mRefreshStatus = STATUS_TOP_EDGE; //两种， private boolean mRefreshViewAdded; public UpRefreshListView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(); } public UpRefreshListView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public UpRefreshListView(Context context) { super(context); init(); } private void init() { MAX_TOP_PADDING = dp2px(100); } private int dp2px(float dp) { final float scale = getResources().getDisplayMetrics().density; return (int) (dp * scale + 0.5f); } /** * 设置顶部显示的加载界面 * * 在setAdapter()之前设置 * @param headerView */ public void setRefreshView(View headerView) { if(null != headerView) { mRefreshView = headerView; } } public void setRefreshView(int resId) { View headerView = inflate(getContext(), resId, null); setRefreshView(headerView); } /** * 当数据加载完成后，调用此方法隐藏刷新视图 */ public void hideRefreshView() { final View headerView = mRefreshView; if(null != headerView && mRefreshViewAdded) { removeHeaderView(headerView); mRefreshViewAdded = false; } } @Override public void setAdapter(ListAdapter adapter) { final boolean needAdd = getHeaderViewsCount() == 0 && getFooterViewsCount() == 0; if(needAdd) { final View headerView = mRefreshView; if(null != headerView && !mRefreshViewAdded) { addHeaderView(headerView); mRefreshViewAdded = true; } super.setAdapter(adapter); if(null != headerView && mRefreshViewAdded) { removeHeaderView(headerView); mRefreshViewAdded = false; } } else { super.setAdapter(adapter); } } public OnRefreshStatusListener getStatusListener() { return mStatusListener; } public void setStatusListener(OnRefreshStatusListener mStatusListener) { this.mStatusListener = mStatusListener; } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); final View view = mRefreshView; if(-1 == mOldTopPadding && null != view) { mOldTopPadding = view.getPaddingTop(); } } @Override public boolean onTouchEvent(MotionEvent ev) {//列表位于顶端，再向上拉时才处理 if(null != mRefreshView && getFirstVisiblePosition() == 0 && ev.getEdgeFlags() == 0) { processTouch(ev); } return super.onTouchEvent(ev); } private void processTouch(MotionEvent ev) { int action = ev.getAction(); float y = ev.getY(); switch (action) { case MotionEvent.ACTION_DOWN: mLastY = y; break; case MotionEvent.ACTION_MOVE: { int topPadding = (int) (y - mLastY) ; if(0 > topPadding) { topPadding = 0; } else if(topPadding > MAX_TOP_PADDING) { topPadding = MAX_TOP_PADDING; } final View headerView = mRefreshView; if(!mRefreshViewAdded) { //下拉重新添加顶部刷新界面 mRefreshViewAdded = true; addRefreshView(headerView); } int status = mRefreshStatus; if(mStatusListener != null && status == STATUS_TOP_EDGE && topPadding >= MAX_TOP_PADDING / 2 //提前一半，开始显示刷新提示 && null != headerView) { mRefreshStatus = status = STATUS_BOTTOM_EDGE; mStatusListener.onStatusChanaged(headerView, status); } topPadding += mOldTopPadding; //在原有padding基础上增加 setTopPadding(topPadding); break; } case MotionEvent.ACTION_UP: { //抬起，匀速复原 if(null == mTranslate) { final View v = mRefreshView; final int end = mOldTopPadding, start = v.getPaddingTop(); if(start > 0) { mTranslate = new TranslateHelper(start, end); postDelayed(mTranslate, TranslateHelper.INTERVAL); } } break; } default: break; } } private void addRefreshView(View v) { boolean executed = false; try { Field f = getClass().getDeclaredField("mHeaderViewInfos"); if(null != f) { Object obj = f.get(this); if(obj instanceof java.util.List) {//绕开必须setAdapter()前添加HeaderView限制 List<FixedViewInfo> mHeaderViewInfos = (List<FixedViewInfo>) obj; FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = null; info.isSelectable = false; mHeaderViewInfos.add(0,info); //添加刷新视图到HeaderView第一项 executed = true; } } } catch (Exception e) { // e.printStackTrace(); } if(!executed) { //没有执行，将调用ListView提供的API ListAdapter adapter = getAdapter(); if(adapter instanceof HeaderViewListAdapter) { adapter = ((HeaderViewListAdapter)adapter).getWrappedAdapter(); } super.setAdapter(null); addHeaderView(v); super.setAdapter(adapter); } } public static interface OnRefreshStatusListener { static final int STATUS_BOTTOM_EDGE = 1; //此时被完全拉起 static final int STATUS_TOP_EDGE = 0; //默认位置或拉起后恢复位置 void onStatusChanaged(View v, int status); } private class TranslateHelper implements Runnable { int end, current; int SPEED = 15; //移动速度 static final int INTERVAL = 10; //间隔时间（毫秒） public TranslateHelper(int start, int end) { this.end = end; this.current = start; SPEED = dp2px(SPEED); } @Override public void run() { current -= SPEED; if(current < end) { current = end; } setTopPadding(current); if(current == end) { removeCallbacks(this); mTranslate = null; final View headerView = mRefreshView; int status = mRefreshStatus; if(status == STATUS_BOTTOM_EDGE && mStatusListener != null && null != headerView) { mRefreshStatus = status = STATUS_TOP_EDGE; mStatusListener.onStatusChanaged(headerView, status); } } else { postDelayed(this, INTERVAL); } } } private void setTopPadding(int topPadding) { final View view = mRefreshView; if(null != view) { view.setPadding(view.getPaddingLeft(), topPadding, view.getPaddingRight(), view.getPaddingBottom()); } } }