官方地址

https://github.com/liaohuqiu/android-Ultra-Pull-To-Refresh

簡(jiǎn)單使用

PtrClassicDefaultHeader header = new PtrClassicDefaultHeader(this);        
ptrFrameLayout.addPtrUIHandler(header);
ptrFrameLayout.setHeaderView(header);
ptrFrameLayout.setPtrHandler(new PtrDefaultHandler() {
      @Override
      public void onRefreshBegin(PtrFrameLayout frame) {
          refresh();
      }
 });

PtrUIHandler接口

它的實(shí)現(xiàn)類(lèi)為PtrClassicDefaultHeader慨绳、MaterialHeader、StoreHouseHeader、PtrUIHandlerHolder臼膏。

1鹉胖、前三者為下拉刷新不同樣式的實(shí)現(xiàn)類(lèi)辫狼，可通過(guò)此接口自定義下拉刷新樣式露该，接口方法如下：

• 開(kāi)始下拉译暂，此方法之后status = 2(PTR_STATUS_PREPARE)

public void onUIRefreshPrepare(PtrFrameLayout frame);

• 開(kāi)始刷新扎附，此方法之后status = 3(PTR_STATUS_LOADING)

public void onUIRefreshBegin(PtrFrameLayout frame);

• 刷新完成蔫耽，此方法之后status = 4(PTR_STATUS_COMPLETE)

public void onUIRefreshComplete(PtrFrameLayout frame);

• 恢復(fù)UI ，此方法之后status = 1(PTR_STATUS_INIT)

public void onUIReset(PtrFrameLayout frame);

• 下拉刷新過(guò)程中位置回調(diào)

public void onUIPositionChange(PtrFrameLayout frame, boolean isUnderTouch, byte status, PtrIndicator ptrIndicator);

2留夜、PtrUIHandlerHolder是PtrUIHandler的持有者匙铡。內(nèi)置靜態(tài)方法addHandler、removeHandler碍粥，用于添加和移除PtrUIHandler鳖眼。一個(gè)PtrUIHandlerHolder對(duì)象可以看作是鏈表結(jié)構(gòu)的一個(gè)節(jié)點(diǎn)，在實(shí)現(xiàn)PtrUIHandler上述5個(gè)方法時(shí)嚼摩，遍歷所有的鏈表節(jié)點(diǎn)钦讳，調(diào)用對(duì)應(yīng)的接口方法。

PtrFrameLayout

自定義屬性

// 頭部
<attr name="ptr_header" format="reference" />
// 內(nèi)容
<attr name="ptr_content" format="reference" />
// 阻尼系數(shù)枕面，默認(rèn)1.7f愿卒，越大感覺(jué)下拉時(shí)越吃力
<attr name="ptr_resistance" format="float" />
// 觸發(fā)刷新時(shí)移動(dòng)的位置比例，默認(rèn)1.2f潮秘，移動(dòng)達(dá)到頭部高度1.2倍時(shí)可觸發(fā)刷新操作
<attr name="ptr_ratio_of_header_height_to_refresh" format="float" />
// 回彈延時(shí)琼开，默認(rèn) 200ms，回彈到刷新高度所用時(shí)間
<attr name="ptr_duration_to_close" format="integer" />

// 頭部回彈時(shí)間枕荞，默認(rèn)1000ms
<attr name="ptr_duration_to_close_header" format="integer" />
// 下拉刷新/釋放刷新柜候，默認(rèn)釋放刷新
<attr name="ptr_pull_to_fresh" format="boolean" />
// 刷新時(shí)保持頭部搞动，默認(rèn)true
<attr name="ptr_keep_header_when_refresh" format="boolean" />

onMeasure方法

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    // 測(cè)量headerView的寬高
    if (mHeaderView != null) {
        measureChildWithMargins(mHeaderView, widthMeasureSpec, 0, heightMeasureSpec, 0);
        MarginLayoutParams lp = (MarginLayoutParams) mHeaderView.getLayoutParams();
        mHeaderHeight = mHeaderView.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
        mPtrIndicator.setHeaderHeight(mHeaderHeight);
    }
    // 對(duì)ContentView進(jìn)行測(cè)量
    if (mContent != null) {
        measureContentView(mContent, widthMeasureSpec, heightMeasureSpec);
    }
}

private void measureContentView(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
    final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
    final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
            getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin, lp.width);
    final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
            getPaddingTop() + getPaddingBottom() + lp.topMargin, lp.height);
    child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}

調(diào)用measureChildWithMargins方法對(duì)HeaderView進(jìn)行測(cè)量，獲得headerView高度
調(diào)用getChildMeasureSpec(int spec, int padding, int childDimension)獲得子View的MeasureSpec渣刷，調(diào)用child.measure(childWidthMeasureSpec, childHeightMeasureSpec)鹦肿，對(duì)ContentView進(jìn)行測(cè)量

onLayout方法

protected void onLayout(boolean flag, int i, int j, int k, int l) {
    layoutChildren();
}

private void layoutChildren() {
    int offset = mPtrIndicator.getCurrentPosY();
    int paddingLeft = getPaddingLeft();
    int paddingTop = getPaddingTop();
    // 對(duì)HeaderView進(jìn)行l(wèi)ayout，主要是top的計(jì)算
    if (mHeaderView != null) {
        MarginLayoutParams lp = (MarginLayoutParams) mHeaderView.getLayoutParams();
        final int left = paddingLeft + lp.leftMargin;
        // enhance readability(header is layout above screen when first init)
        final int top = -(mHeaderHeight - paddingTop - lp.topMargin - offset);
        final int right = left + mHeaderView.getMeasuredWidth();
        final int bottom = top + mHeaderView.getMeasuredHeight();
        mHeaderView.layout(left, top, right, bottom);
    }
    // 對(duì)ContentView進(jìn)行l(wèi)ayout
    if (mContent != null) {
        if (isPinContent()) {
            offset = 0;
        }
        MarginLayoutParams lp = (MarginLayoutParams) mContent.getLayoutParams();
        final int left = paddingLeft + lp.leftMargin;
        final int top = paddingTop + lp.topMargin + offset;
        final int right = left + mContent.getMeasuredWidth();
        final int bottom = top + mContent.getMeasuredHeight();
        mContent.layout(left, top, right, bottom);
    }
}

dispatchTouchEvent方法

public boolean dispatchTouchEvent(MotionEvent e) {
    if (!isEnabled() || mContent == null || mHeaderView == null) {
        return dispatchTouchEventSupper(e);
    }
    int action = e.getAction();
    switch (action) {
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            mPtrIndicator.onRelease();
            if (mPtrIndicator.hasLeftStartPosition()) {
                // 松手的位置大于初始位置
                onRelease(false);
                if (mPtrIndicator.hasMovedAfterPressedDown()) {
                    sendCancelEvent();
                    return true;
                }
                return dispatchTouchEventSupper(e);
            } else {
                return dispatchTouchEventSupper(e);
            }

        case MotionEvent.ACTION_DOWN:
            mHasSendCancelEvent = false;
            // 記錄按下的位置
            mPtrIndicator.onPressDown(e.getX(), e.getY());
            mScrollChecker.abortIfWorking();
            // 重置水平方向阻止標(biāo)記
            mPreventForHorizontal = false;
            // The cancel event will be sent once the position is moved.
            // So let the event pass to children.
            // fix #93, #102
            dispatchTouchEventSupper(e);
            return true;
            
        case MotionEvent.ACTION_MOVE:
            mLastMoveEvent = e;
            mPtrIndicator.onMove(e.getX(), e.getY());
            // 相對(duì)上次位置偏移量(阻尼系數(shù)轉(zhuǎn)化后)
            float offsetX = mPtrIndicator.getOffsetX();
            float offsetY = mPtrIndicator.getOffsetY();
            // 水平方向移動(dòng)較大辅柴，事件可以繼續(xù)分發(fā)下去
            if (mDisableWhenHorizontalMove && !mPreventForHorizontal && (Math.abs(offsetX) > mPagingTouchSlop && Math.abs(offsetX) > Math.abs(offsetY))) {
                if (mPtrIndicator.isInStartPosition()) {
                    mPreventForHorizontal = true;
                }
            }
            if (mPreventForHorizontal) {
                return dispatchTouchEventSupper(e);
            }
            boolean moveDown = offsetY > 0;
            boolean moveUp = !moveDown;
            boolean canMoveUp = mPtrIndicator.hasLeftStartPosition();
            // disable move when header not reach top
            if (moveDown && mPtrHandler != null && !mPtrHandler.checkCanDoRefresh(this, mContent, mHeaderView)) {
                return dispatchTouchEventSupper(e);
            }
            if ((moveUp && canMoveUp) || moveDown) {
                movePos(offsetY);
                return true;
            }
    }
    return dispatchTouchEventSupper(e);
}

位置更新方法

private void updatePos(int change) {
    if (change == 0) {
        return;
    }
    boolean isUnderTouch = mPtrIndicator.isUnderTouch();
    // once moved, cancel event will be sent to child
    if (isUnderTouch && !mHasSendCancelEvent && mPtrIndicator.hasMovedAfterPressedDown()) {
        mHasSendCancelEvent = true;
        sendCancelEvent();
    }
    // leave initiated position or just refresh complete
    if ((mPtrIndicator.hasJustLeftStartPosition() && mStatus == PTR_STATUS_INIT) ||
            (mPtrIndicator.goDownCrossFinishPosition() && mStatus == PTR_STATUS_COMPLETE && isEnabledNextPtrAtOnce())) {
        mStatus = PTR_STATUS_PREPARE;
        mPtrUIHandlerHolder.onUIRefreshPrepare(this);
    }
    // back to initiated position
    if (mPtrIndicator.hasJustBackToStartPosition()) {
        tryToNotifyReset();
        // recover event to children
        if (isUnderTouch) {
            sendDownEvent();
        }
    }
    // Pull to Refresh
    if (mStatus == PTR_STATUS_PREPARE) {
        // reach fresh height while moving from top to bottom
        if (isUnderTouch && !isAutoRefresh() && mPullToRefresh
                && mPtrIndicator.crossRefreshLineFromTopToBottom()) {
            tryToPerformRefresh();
        }
        // reach header height while auto refresh
        if (performAutoRefreshButLater() && mPtrIndicator.hasJustReachedHeaderHeightFromTopToBottom()) {
            tryToPerformRefresh();
        }
    }
    // 核心移動(dòng)方法
    mHeaderView.offsetTopAndBottom(change);
    if (!isPinContent()) {
        mContent.offsetTopAndBottom(change);
    }
    invalidate();
    if (mPtrUIHandlerHolder.hasHandler()) {
        mPtrUIHandlerHolder.onUIPositionChange(this, isUnderTouch, mStatus, mPtrIndicator);
    }
    onPositionChange(isUnderTouch, mStatus, mPtrIndicator);
}