編輯：關於android開發
主要使用到的類：
NestedScrollingChild NestedScrollingParent下面這個類是V4包中提供的一個實用類，實現滑動刷新主要就靠他了。
代碼分析：
需要關注的方法：
package android.support.v4.widget;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.support.annotation.ColorInt;
import android.support.annotation.ColorRes;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.NestedScrollingParent;
import android.support.v4.view.NestedScrollingParentHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.DecelerateInterpolator;
import android.view.animation.Transformation;
import android.widget.AbsListView;
//這裡給出重要的注釋，簡單的地方就不寫了
/**
* SwipeRefreshLayout應該被用在想實現垂直滑動跟新內容的地方。使用這個View的Activity要添加OnRefreshListener監聽，當發生滑動事件的時候會受到通知。在監聽中應該在完成刷新操作後確認刷新操作完成（調用setRefreshing(false)）。如果一個Activity只是想要顯示一個progress，可以調用setRefreshing(true)。取消View的手勢監聽要調用setEnabled(false)；
*/
public class SwipeRefreshLayout extends ViewGroup implements NestedScrollingParent,
NestedScrollingChild {
// Maps to ProgressBar.Large style
public static final int LARGE = MaterialProgressDrawable.LARGE;
// Maps to ProgressBar default style
public static final int DEFAULT = MaterialProgressDrawable.DEFAULT;
private static final String LOG_TAG = SwipeRefreshLayout.class.getSimpleName();
private static final int MAX_ALPHA = 255;
private static final int STARTING_PROGRESS_ALPHA = (int) (.3f * MAX_ALPHA);
private static final int CIRCLE_DIAMETER = 40;
private static final int CIRCLE_DIAMETER_LARGE = 56;
private static final float DECELERATE_INTERPOLATION_FACTOR = 2f;
private static final int INVALID_POINTER = -1;
private static final float DRAG_RATE = .5f;
// Max amount of circle that can be filled by progress during swipe gesture,
// where 1.0 is a full circle
private static final float MAX_PROGRESS_ANGLE = .8f;
private static final int SCALE_DOWN_DURATION = 150;
private static final int ALPHA_ANIMATION_DURATION = 300;
private static final int ANIMATE_TO_TRIGGER_DURATION = 200;
private static final int ANIMATE_TO_START_DURATION = 200;
// Default background for the progress spinner
private static final int CIRCLE_BG_LIGHT = 0xFFFAFAFA;
// Default offset in dips from the top of the view to where the progress spinner should stop
private static final int DEFAULT_CIRCLE_TARGET = 64;
private View mTarget; // the target of the gesture
private OnRefreshListener mListener;
private boolean mRefreshing = false;
private int mTouchSlop;
private float mTotalDragDistance = -1;
// If nested scrolling is enabled, the total amount that needed to be
// consumed by this as the nested scrolling parent is used in place of the
// overscroll determined by MOVE events in the onTouch handler
private float mTotalUnconsumed;
private final NestedScrollingParentHelper mNestedScrollingParentHelper;
private final NestedScrollingChildHelper mNestedScrollingChildHelper;
private final int[] mParentScrollConsumed = new int[2];
private int mMediumAnimationDuration;
private int mCurrentTargetOffsetTop;
// Whether or not the starting offset has been determined.
private boolean mOriginalOffsetCalculated = false;
private float mInitialMotionY;
private float mInitialDownY;
private boolean mIsBeingDragged;
private int mActivePointerId = INVALID_POINTER;
// Whether this item is scaled up rather than clipped
private boolean mScale;
// Target is returning to its start offset because it was cancelled or a
// refresh was triggered.
private boolean mReturningToStart;
private final DecelerateInterpolator mDecelerateInterpolator;
private static final int[] LAYOUT_ATTRS = new int[] {
android.R.attr.enabled
};
private CircleImageView mCircleView;
private int mCircleViewIndex = -1;
protected int mFrom;
private float mStartingScale;
protected int mOriginalOffsetTop;
private MaterialProgressDrawable mProgress;
private Animation mScaleAnimation;
private Animation mScaleDownAnimation;
private Animation mAlphaStartAnimation;
private Animation mAlphaMaxAnimation;
private Animation mScaleDownToStartAnimation;
private float mSpinnerFinalOffset;
private boolean mNotify;
private int mCircleWidth;
private int mCircleHeight;
// Whether the client has set a custom starting position;
private boolean mUsingCustomStart;
private Animation.AnimationListener mRefreshListener = new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
}
@Override
public void onAnimationRepeat(Animation animation) {
}
@Override
public void onAnimationEnd(Animation animation) {
if (mRefreshing) {
// Make sure the progress view is fully visible
mProgress.setAlpha(MAX_ALPHA);
mProgress.start();
if (mNotify) {
if (mListener != null) {
mListener.onRefresh();
}
}
} else {
mProgress.stop();
mCircleView.setVisibility(View.GONE);
setColorViewAlpha(MAX_ALPHA);
// Return the circle to its start position
if (mScale) {
setAnimationProgress(0 /* animation complete and view is hidden */);
} else {
setTargetOffsetTopAndBottom(mOriginalOffsetTop - mCurrentTargetOffsetTop,
true /* requires update */);
}
}
mCurrentTargetOffsetTop = mCircleView.getTop();
}
};
private void setColorViewAlpha(int targetAlpha) {
mCircleView.getBackground().setAlpha(targetAlpha);
mProgress.setAlpha(targetAlpha);
}
/**
* The refresh indicator starting and resting position is always positioned
* near the top of the refreshing content. This position is a consistent
* location, but can be adjusted in either direction based on whether or not
* there is a toolbar or actionbar present.
*
* @param scale Set to true if there is no view at a higher z-order than
* where the progress spinner is set to appear.
* @param start The offset in pixels from the top of this view at which the
* progress spinner should appear.
* @param end The offset in pixels from the top of this view at which the
* progress spinner should come to rest after a successful swipe
* gesture.
*/
public void setProgressViewOffset(boolean scale, int start, int end) {
mScale = scale;
mCircleView.setVisibility(View.GONE);
mOriginalOffsetTop = mCurrentTargetOffsetTop = start;
mSpinnerFinalOffset = end;
mUsingCustomStart = true;
mCircleView.invalidate();
}
/**
* The refresh indicator resting position is always positioned near the top
* of the refreshing content. This position is a consistent location, but
* can be adjusted in either direction based on whether or not there is a
* toolbar or actionbar present.
*
* @param scale Set to true if there is no view at a higher z-order than
* where the progress spinner is set to appear.
* @param end The offset in pixels from the top of this view at which the
* progress spinner should come to rest after a successful swipe
* gesture.
*/
public void setProgressViewEndTarget(boolean scale, int end) {
mSpinnerFinalOffset = end;
mScale = scale;
mCircleView.invalidate();
}
/**
* One of DEFAULT, or LARGE.
*/
public void setSize(int size) {
if (size != MaterialProgressDrawable.LARGE && size != MaterialProgressDrawable.DEFAULT) {
return;
}
final DisplayMetrics metrics = getResources().getDisplayMetrics();
if (size == MaterialProgressDrawable.LARGE) {
mCircleHeight = mCircleWidth = (int) (CIRCLE_DIAMETER_LARGE * metrics.density);
} else {
mCircleHeight = mCircleWidth = (int) (CIRCLE_DIAMETER * metrics.density);
}
// force the bounds of the progress circle inside the circle view to
// update by setting it to null before updating its size and then
// re-setting it
mCircleView.setImageDrawable(null);
mProgress.updateSizes(size);
mCircleView.setImageDrawable(mProgress);
}
/**
* Simple constructor to use when creating a SwipeRefreshLayout from code.
*
* @param context
*/
public SwipeRefreshLayout(Context context) {
this(context, null);
}
/**
* Constructor that is called when inflating SwipeRefreshLayout from XML.
*
* @param context
* @param attrs
*/
public SwipeRefreshLayout(Context context, AttributeSet attrs) {
super(context, attrs);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
mMediumAnimationDuration = getResources().getInteger(
android.R.integer.config_mediumAnimTime);
//設置為false，不會調用draw方法
setWillNotDraw(false);
mDecelerateInterpolator = new DecelerateInterpolator(DECELERATE_INTERPOLATION_FACTOR);
final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS);
setEnabled(a.getBoolean(0, true));
a.recycle();
final DisplayMetrics metrics = getResources().getDisplayMetrics();
mCircleWidth = (int) (CIRCLE_DIAMETER * metrics.density);
mCircleHeight = (int) (CIRCLE_DIAMETER * metrics.density);
//創建progress
createProgressView();
//設置當前view添加childView的順序由getChildDrawingOrder方法決定。因為目前繼承自Viewgroup
ViewCompat.setChildrenDrawingOrderEnabled(this, true);
// the absolute offset has to take into account that the circle starts at an offset
mSpinnerFinalOffset = DEFAULT_CIRCLE_TARGET * metrics.density;
mTotalDragDistance = mSpinnerFinalOffset;
mNestedScrollingParentHelper = new NestedScrollingParentHelper(this);
mNestedScrollingChildHelper = new NestedScrollingChildHelper(this);
//設置可以使用嵌套滑動
setNestedScrollingEnabled(true);
}
//指定添加View的方式，吧progress放在最後一個添加
//基本邏輯，mCircleViewIndex記錄了progress的位置。如果添加的是Progress之前的View，直接返回。如果是progress之後的View那麼就i+1.為什麼要加1呢？可以這麼想，View的位置是在OnLayout中指定的，而View是存放在一個List中。添加View的時候會遍歷list，從0開始取。一共childCount個view ,i表示當前要添加第i個。當添加到mCircleViewIndex個時，因為我想講progress添加到左後，所以要跳過mCircleViewIndex這個，取下一個。我想，夠清楚了。
protected int getChildDrawingOrder(int childCount, int i) {
if (mCircleViewIndex < 0) {
return i;
} else if (i == childCount - 1) {
// Draw the selected child last
return mCircleViewIndex;
} else if (i >= mCircleViewIndex) {
// Move the children after the selected child earlier one
return i + 1;
} else {
// Keep the children before the selected child the same
return i;
}
}
private void createProgressView() {
mCircleView = new CircleImageView(getContext(), CIRCLE_BG_LIGHT, CIRCLE_DIAMETER/2);
mProgress = new MaterialProgressDrawable(getContext(), this);
mProgress.setBackgroundColor(CIRCLE_BG_LIGHT);
mCircleView.setImageDrawable(mProgress);
mCircleView.setVisibility(View.GONE);
addView(mCircleView);
}
/**
* Set the listener to be notified when a refresh is triggered via the swipe
* gesture.
*/
public void setOnRefreshListener(OnRefreshListener listener) {
mListener = listener;
}
/**
* Pre API 11, alpha is used to make the progress circle appear instead of scale.
*/
private boolean isAlphaUsedForScale() {
return android.os.Build.VERSION.SDK_INT < 11;
}
/**
設置當前View刷新狀態改變（正在刷新 true OR false）
不能再進行刷新操作的時候調用
* Notify the widget that refresh state has changed. Do not call this when
* refresh is triggered by a swipe gesture.
*
* @param refreshing Whether or not the view should show refresh progress.
*/
public void setRefreshing(boolean refreshing) {
if (refreshing && mRefreshing != refreshing) {
// scale and show
mRefreshing = refreshing;
int endTarget = 0;
if (!mUsingCustomStart) {
endTarget = (int) (mSpinnerFinalOffset + mOriginalOffsetTop);
} else {
endTarget = (int) mSpinnerFinalOffset;
}
setTargetOffsetTopAndBottom(endTarget - mCurrentTargetOffsetTop,
true /* requires update */);
mNotify = false;
startScaleUpAnimation(mRefreshListener);
} else {
setRefreshing(refreshing, false /* notify */);
}
}
private void startScaleUpAnimation(AnimationListener listener) {
mCircleView.setVisibility(View.VISIBLE);
if (android.os.Build.VERSION.SDK_INT >= 11) {
// Pre API 11, alpha is used in place of scale up to show the
// progress circle appearing.
// Don't adjust the alpha during appearance otherwise.
mProgress.setAlpha(MAX_ALPHA);
}
mScaleAnimation = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
setAnimationProgress(interpolatedTime);
}
};
mScaleAnimation.setDuration(mMediumAnimationDuration);
if (listener != null) {
mCircleView.setAnimationListener(listener);
}
mCircleView.clearAnimation();
mCircleView.startAnimation(mScaleAnimation);
}
/**
* Pre API 11, this does an alpha animation.
* @param progress
*/
private void setAnimationProgress(float progress) {
if (isAlphaUsedForScale()) {
setColorViewAlpha((int) (progress * MAX_ALPHA));
} else {
ViewCompat.setScaleX(mCircleView, progress);
ViewCompat.setScaleY(mCircleView, progress);
}
}
private void setRefreshing(boolean refreshing, final boolean notify) {
if (mRefreshing != refreshing) {
mNotify = notify;
ensureTarget();
mRefreshing = refreshing;
if (mRefreshing) {
animateOffsetToCorrectPosition(mCurrentTargetOffsetTop, mRefreshListener);
} else {
startScaleDownAnimation(mRefreshListener);
}
}
}
private void startScaleDownAnimation(Animation.AnimationListener listener) {
mScaleDownAnimation = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
setAnimationProgress(1 - interpolatedTime);
}
};
mScaleDownAnimation.setDuration(SCALE_DOWN_DURATION);
mCircleView.setAnimationListener(listener);
mCircleView.clearAnimation();
mCircleView.startAnimation(mScaleDownAnimation);
}
private void startProgressAlphaStartAnimation() {
mAlphaStartAnimation = startAlphaAnimation(mProgress.getAlpha(), STARTING_PROGRESS_ALPHA);
}
private void startProgressAlphaMaxAnimation() {
mAlphaMaxAnimation = startAlphaAnimation(mProgress.getAlpha(), MAX_ALPHA);
}
private Animation startAlphaAnimation(final int startingAlpha, final int endingAlpha) {
// Pre API 11, alpha is used in place of scale. Don't also use it to
// show the trigger point.
if (mScale && isAlphaUsedForScale()) {
return null;
}
Animation alpha = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
mProgress
.setAlpha((int) (startingAlpha+ ((endingAlpha - startingAlpha)
* interpolatedTime)));
}
};
alpha.setDuration(ALPHA_ANIMATION_DURATION);
// Clear out the previous animation listeners.
mCircleView.setAnimationListener(null);
mCircleView.clearAnimation();
mCircleView.startAnimation(alpha);
return alpha;
}
/**
* @deprecated Use {@link #setProgressBackgroundColorSchemeResource(int)}
*/
@Deprecated
public void setProgressBackgroundColor(int colorRes) {
setProgressBackgroundColorSchemeResource(colorRes);
}
/**
* Set the background color of the progress spinner disc.
*
* @param colorRes Resource id of the color.
*/
public void setProgressBackgroundColorSchemeResource(@ColorRes int colorRes) {
setProgressBackgroundColorSchemeColor(getResources().getColor(colorRes));
}
/**
* Set the background color of the progress spinner disc.
*
* @param color
*/
public void setProgressBackgroundColorSchemeColor(@ColorInt int color) {
mCircleView.setBackgroundColor(color);
mProgress.setBackgroundColor(color);
}
/**
* @deprecated Use {@link #setColorSchemeResources(int...)}
*/
@Deprecated
public void setColorScheme(@ColorInt int... colors) {
setColorSchemeResources(colors);
}
/**
* Set the color resources used in the progress animation from color resources.
* The first color will also be the color of the bar that grows in response
* to a user swipe gesture.
*
* @param colorResIds
*/
public void setColorSchemeResources(@ColorRes int... colorResIds) {
final Resources res = getResources();
int[] colorRes = new int[colorResIds.length];
for (int i = 0; i < colorResIds.length; i++) {
colorRes[i] = res.getColor(colorResIds[i]);
}
setColorSchemeColors(colorRes);
}
/**
* Set the colors used in the progress animation. The first
* color will also be the color of the bar that grows in response to a user
* swipe gesture.
*
* @param colors
*/
@ColorInt
public void setColorSchemeColors(int... colors) {
ensureTarget();
mProgress.setColorSchemeColors(colors);
}
/**
* @return Whether the SwipeRefreshWidget is actively showing refresh
* progress.
*/
public boolean isRefreshing() {
return mRefreshing;
}
private void ensureTarget() {
// Don't bother getting the parent height if the parent hasn't been laid
// out yet.
if (mTarget == null) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (!child.equals(mCircleView)) {
mTarget = child;
break;
}
}
}
}
/**
* Set the distance to trigger a sync in dips
*
* @param distance
*/
public void setDistanceToTriggerSync(int distance) {
mTotalDragDistance = distance;
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
final int width = getMeasuredWidth();
final int height = getMeasuredHeight();
if (getChildCount() == 0) {
return;
}
if (mTarget == null) {
ensureTarget();
}
if (mTarget == null) {
return;
}
final View child = mTarget;
final int childLeft = getPaddingLeft();
final int childTop = getPaddingTop();
final int childWidth = width - getPaddingLeft() - getPaddingRight();
final int childHeight = height - getPaddingTop() - getPaddingBottom();
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
int circleWidth = mCircleView.getMeasuredWidth();
int circleHeight = mCircleView.getMeasuredHeight();
mCircleView.layout((width / 2 - circleWidth / 2), mCurrentTargetOffsetTop,
(width / 2 + circleWidth / 2), mCurrentTargetOffsetTop + circleHeight);
}
@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (mTarget == null) {
ensureTarget();
}
if (mTarget == null) {
return;
}
mTarget.measure(MeasureSpec.makeMeasureSpec(
getMeasuredWidth() - getPaddingLeft() - getPaddingRight(),
MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(
getMeasuredHeight() - getPaddingTop() - getPaddingBottom(), MeasureSpec.EXACTLY));
mCircleView.measure(MeasureSpec.makeMeasureSpec(mCircleWidth, MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(mCircleHeight, MeasureSpec.EXACTLY));
if (!mUsingCustomStart && !mOriginalOffsetCalculated) {
mOriginalOffsetCalculated = true;
mCurrentTargetOffsetTop = mOriginalOffsetTop = -mCircleView.getMeasuredHeight();
}
mCircleViewIndex = -1;
// Get the index of the circleview.
for (int index = 0; index < getChildCount(); index++) {
if (getChildAt(index) == mCircleView) {
mCircleViewIndex = index;
break;
}
}
}
/**
* Get the diameter of the progress circle that is displayed as part of the
* swipe to refresh layout. This is not valid until a measure pass has
* completed.
*
* @return Diameter in pixels of the progress circle view.
*/
public int getProgressCircleDiameter() {
return mCircleView != null ?mCircleView.getMeasuredHeight() : 0;
}
/**
* @return Whether it is possible for the child view of this layout to
* scroll up. Override this if the child view is a custom view.
*/
public boolean canChildScrollUp() {
if (android.os.Build.VERSION.SDK_INT < 14) {
if (mTarget instanceof AbsListView) {
final AbsListView absListView = (AbsListView) mTarget;
return absListView.getChildCount() > 0
&& (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0)
.getTop() < absListView.getPaddingTop());
} else {
return ViewCompat.canScrollVertically(mTarget, -1) || mTarget.getScrollY() > 0;
}
} else {
return ViewCompat.canScrollVertically(mTarget, -1);
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
ensureTarget();
final int action = MotionEventCompat.getActionMasked(ev);
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp() || mRefreshing) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
setTargetOffsetTopAndBottom(mOriginalOffsetTop - mCircleView.getTop(), true);
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
final float initialDownY = getMotionEventY(ev, mActivePointerId);
if (initialDownY == -1) {
return false;
}
mInitialDownY = initialDownY;
break;
case MotionEvent.ACTION_MOVE:
if (mActivePointerId == INVALID_POINTER) {
Log.e(LOG_TAG, "Got ACTION_MOVE event but don't have an active pointer id.");
return false;
}
final float y = getMotionEventY(ev, mActivePointerId);
if (y == -1) {
return false;
}
final float yDiff = y - mInitialDownY;
if (yDiff > mTouchSlop && !mIsBeingDragged) {
mInitialMotionY = mInitialDownY + mTouchSlop;
mIsBeingDragged = true;
mProgress.setAlpha(STARTING_PROGRESS_ALPHA);
}
break;
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
break;
}
return mIsBeingDragged;
}
private float getMotionEventY(MotionEvent ev, int activePointerId) {
final int index = MotionEventCompat.findPointerIndex(ev, activePointerId);
if (index < 0) {
return -1;
}
return MotionEventCompat.getY(ev, index);
}
@Override
public void requestDisallowInterceptTouchEvent(boolean b) {
// if this is a List < L or another view that doesn't support nested
// scrolling, ignore this request so that the vertical scroll event
// isn't stolen
if ((android.os.Build.VERSION.SDK_INT < 21 && mTarget instanceof AbsListView)
|| (mTarget != null && !ViewCompat.isNestedScrollingEnabled(mTarget))) {
// Nope.
} else {
super.requestDisallowInterceptTouchEvent(b);
}
}
// NestedScrollingParent
@Override
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
if (isEnabled() && !mReturningToStart && !canChildScrollUp() && !mRefreshing
&& (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0) {
// Dispatch up to the nested parent
startNestedScroll(nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL);
return true;
}
return false;
}
@Override
public void onNestedScrollAccepted(View child, View target, int axes) {
// Reset the counter of how much leftover scroll needs to be consumed.
mNestedScrollingParentHelper.onNestedScrollAccepted(child, target, axes);
mTotalUnconsumed = 0;
}
@Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
// If we are in the middle of consuming, a scroll, then we want to move the spinner back up
// before allowing the list to scroll
if (dy > 0 && mTotalUnconsumed > 0) {
if (dy > mTotalUnconsumed) {
consumed[1] = dy - (int) mTotalUnconsumed;
mTotalUnconsumed = 0;
} else {
mTotalUnconsumed -= dy;
consumed[1] = dy;
}
moveSpinner(mTotalUnconsumed);
}
// If a client layout is using a custom start position for the circle
// view, they mean to hide it again before scrolling the child view
// If we get back to mTotalUnconsumed == 0 and there is more to go, hide
// the circle so it isn't exposed if its blocking content is moved
if (mUsingCustomStart && dy > 0 && mTotalUnconsumed == 0
&& Math.abs(dy - consumed[1]) > 0) {
mCircleView.setVisibility(View.GONE);
}
// Now let our nested parent consume the leftovers
final int[] parentConsumed = mParentScrollConsumed;
if (dispatchNestedPreScroll(dx - consumed[0], dy - consumed[1], parentConsumed, null)) {
consumed[0] += parentConsumed[0];
consumed[1] += parentConsumed[1];
}
}
@Override
public int getNestedScrollAxes() {
return mNestedScrollingParentHelper.getNestedScrollAxes();
}
@Override
public void onStopNestedScroll(View target) {
mNestedScrollingParentHelper.onStopNestedScroll(target);
// Finish the spinner for nested scrolling if we ever consumed any
// unconsumed nested scroll
if (mTotalUnconsumed > 0) {
finishSpinner(mTotalUnconsumed);
mTotalUnconsumed = 0;
}
// Dispatch up our nested parent
stopNestedScroll();
}
@Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed) {
if (dyUnconsumed < 0) {
dyUnconsumed = Math.abs(dyUnconsumed);
mTotalUnconsumed += dyUnconsumed;
moveSpinner(mTotalUnconsumed);
}
// Dispatch up to the nested parent
dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dxConsumed, null);
}
// NestedScrollingChild
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mNestedScrollingChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean isNestedScrollingEnabled() {
return mNestedScrollingChildHelper.isNestedScrollingEnabled();
}
@Override
public boolean startNestedScroll(int axes) {
return mNestedScrollingChildHelper.startNestedScroll(axes);
}
@Override
public void stopNestedScroll() {
mNestedScrollingChildHelper.stopNestedScroll();
}
@Override
public boolean hasNestedScrollingParent() {
return mNestedScrollingChildHelper.hasNestedScrollingParent();
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, int[] offsetInWindow) {
return mNestedScrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed,
dxUnconsumed, dyUnconsumed, offsetInWindow);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return mNestedScrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}
@Override
public boolean onNestedPreFling(View target, float velocityX,
float velocityY) {
return dispatchNestedPreFling(velocityX, velocityY);
}
@Override
public boolean onNestedFling(View target, float velocityX, float velocityY,
boolean consumed) {
return dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mNestedScrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mNestedScrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
private boolean isAnimationRunning(Animation animation) {
return animation != null && animation.hasStarted() && !animation.hasEnded();
}
private void moveSpinner(float overscrollTop) {
mProgress.showArrow(true);
float originalDragPercent = overscrollTop / mTotalDragDistance;
float dragPercent = Math.min(1f, Math.abs(originalDragPercent));
float adjustedPercent = (float) Math.max(dragPercent - .4, 0) * 5 / 3;
float extraOS = Math.abs(overscrollTop) - mTotalDragDistance;
float slingshotDist = mUsingCustomStart ? mSpinnerFinalOffset - mOriginalOffsetTop
: mSpinnerFinalOffset;
float tensionSlingshotPercent = Math.max(0, Math.min(extraOS, slingshotDist * 2)
/ slingshotDist);
float tensionPercent = (float) ((tensionSlingshotPercent / 4) - Math.pow(
(tensionSlingshotPercent / 4), 2)) * 2f;
float extraMove = (slingshotDist) * tensionPercent * 2;
int targetY = mOriginalOffsetTop + (int) ((slingshotDist * dragPercent) + extraMove);
// where 1.0f is a full circle
if (mCircleView.getVisibility() != View.VISIBLE) {
mCircleView.setVisibility(View.VISIBLE);
}
if (!mScale) {
ViewCompat.setScaleX(mCircleView, 1f);
ViewCompat.setScaleY(mCircleView, 1f);
}
if (overscrollTop < mTotalDragDistance) {
if (mScale) {
setAnimationProgress(overscrollTop / mTotalDragDistance);
}
if (mProgress.getAlpha() > STARTING_PROGRESS_ALPHA
&& !isAnimationRunning(mAlphaStartAnimation)) {
// Animate the alpha
startProgressAlphaStartAnimation();
}
float strokeStart = adjustedPercent * .8f;
mProgress.setStartEndTrim(0f, Math.min(MAX_PROGRESS_ANGLE, strokeStart));
mProgress.setArrowScale(Math.min(1f, adjustedPercent));
} else {
if (mProgress.getAlpha() < MAX_ALPHA && !isAnimationRunning(mAlphaMaxAnimation)) {
// Animate the alpha
startProgressAlphaMaxAnimation();
}
}
float rotation = (-0.25f + .4f * adjustedPercent + tensionPercent * 2) * .5f;
mProgress.setProgressRotation(rotation);
setTargetOffsetTopAndBottom(targetY - mCurrentTargetOffsetTop, true /* requires update */);
}
//滑動完成，通知監聽器
private void finishSpinner(float overscrollTop) {
if (overscrollTop > mTotalDragDistance) {
setRefreshing(true, true /* notify */);
} else {
// cancel refresh
mRefreshing = false;
mProgress.setStartEndTrim(0f, 0f);
Animation.AnimationListener listener = null;
if (!mScale) {
listener = new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
}
@Override
public void onAnimationEnd(Animation animation) {
if (!mScale) {
startScaleDownAnimation(null);
}
}
@Override
public void onAnimationRepeat(Animation animation) {
}
};
}
animateOffsetToStartPosition(mCurrentTargetOffsetTop, listener);
mProgress.showArrow(false);
}
}
/**
對手勢的處理
對手勢的說明：在android4.0之後添加了對多點觸控的支持。
public final int getAction() {
return mAction;
}
對於返回的手勢值 mAction一般都是ACTION_DOWN。ACTION_UP。 ACTION_MOVE。ACTION_CANCEL。ACTION_OUTSIDE（手指超出屏幕），ACTION_POINTER_DOWN（有一個非主要的手指按下了），ACTION_POINTER_UP這些事件類型。
但是為了對多點觸控有更好的支持，對每一種事件類型又添加了下表索引。即為每一個事件類型指明是哪一個手指。
例如：如果mAction的值是0x0000，那麼低八位表示事件類型，高八位指明下標索引。
getActionMasked()是使用 mAction &0xff，返回的是事件類型。
getAction()返回的是mAction
getActionIndex()返回索引值
*/
@Override
public boolean onTouchEvent(MotionEvent ev) {、
final int action = MotionEventCompat.getActionMasked(ev);
int pointerIndex = -1;
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp()) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
//記錄手勢id
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
break;
case MotionEvent.ACTION_MOVE: {
//得到當前ID值對應的索引
pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
if (pointerIndex < 0) {
//無效的ID
Log.e(LOG_TAG, "Got ACTION_MOVE event but have an invalid active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
//mInitialMotionY在onInterceptTouchEvent（）中初始化的
final float overscrollTop = (y - mInitialMotionY) * DRAG_RATE;
if (mIsBeingDragged) {
if (overscrollTop > 0) {
//滑動距離達到指定長度，把progress往下移動一段
moveSpinner(overscrollTop);
} else {
return false;
}
}
break;
}
case MotionEventCompat.ACTION_POINTER_DOWN: {
//有其他手指按下
pointerIndex = MotionEventCompat.getActionIndex(ev);
if (pointerIndex < 0) {
Log.e(LOG_TAG, "Got ACTION_POINTER_DOWN event but have an invalid action index.");
return false;
}
//更新手勢ID
mActivePointerId = MotionEventCompat.getPointerId(ev, pointerIndex);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP: {
//手指抬起
pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
if (pointerIndex < 0) {
Log.e(LOG_TAG, "Got ACTION_UP event but don't have an active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float overscrollTop = (y - mInitialMotionY) * DRAG_RATE;
mIsBeingDragged = false;
//滑動完成
finishSpinner(overscrollTop);
mActivePointerId = INVALID_POINTER;
return false;
}
case MotionEvent.ACTION_CANCEL:
return false;
}
return true;
}
private void animateOffsetToCorrectPosition(int from, AnimationListener listener) {
mFrom = from;
mAnimateToCorrectPosition.reset();
mAnimateToCorrectPosition.setDuration(ANIMATE_TO_TRIGGER_DURATION);
mAnimateToCorrectPosition.setInterpolator(mDecelerateInterpolator);
if (listener != null) {
mCircleView.setAnimationListener(listener);
}
mCircleView.clearAnimation();
mCircleView.startAnimation(mAnimateToCorrectPosition);
}
private void animateOffsetToStartPosition(int from, AnimationListener listener) {
if (mScale) {
// Scale the item back down
startScaleDownReturnToStartAnimation(from, listener);
} else {
mFrom = from;
mAnimateToStartPosition.reset();
mAnimateToStartPosition.setDuration(ANIMATE_TO_START_DURATION);
mAnimateToStartPosition.setInterpolator(mDecelerateInterpolator);
if (listener != null) {
mCircleView.setAnimationListener(listener);
}
mCircleView.clearAnimation();
mCircleView.startAnimation(mAnimateToStartPosition);
}
}
private final Animation mAnimateToCorrectPosition = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
int targetTop = 0;
int endTarget = 0;
if (!mUsingCustomStart) {
endTarget = (int) (mSpinnerFinalOffset - Math.abs(mOriginalOffsetTop));
} else {
endTarget = (int) mSpinnerFinalOffset;
}
targetTop = (mFrom + (int) ((endTarget - mFrom) * interpolatedTime));
int offset = targetTop - mCircleView.getTop();
setTargetOffsetTopAndBottom(offset, false /* requires update */);
mProgress.setArrowScale(1 - interpolatedTime);
}
};
private void moveToStart(float interpolatedTime) {
int targetTop = 0;
targetTop = (mFrom + (int) ((mOriginalOffsetTop - mFrom) * interpolatedTime));
int offset = targetTop - mCircleView.getTop();
setTargetOffsetTopAndBottom(offset, false /* requires update */);
}
private final Animation mAnimateToStartPosition = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
moveToStart(interpolatedTime);
}
};
private void startScaleDownReturnToStartAnimation(int from,
Animation.AnimationListener listener) {
mFrom = from;
if (isAlphaUsedForScale()) {
mStartingScale = mProgress.getAlpha();
} else {
mStartingScale = ViewCompat.getScaleX(mCircleView);
}
mScaleDownToStartAnimation = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
float targetScale = (mStartingScale + (-mStartingScale * interpolatedTime));
setAnimationProgress(targetScale);
moveToStart(interpolatedTime);
}
};
mScaleDownToStartAnimation.setDuration(SCALE_DOWN_DURATION);
if (listener != null) {
mCircleView.setAnimationListener(listener);
}
mCircleView.clearAnimation();
mCircleView.startAnimation(mScaleDownToStartAnimation);
}
private void setTargetOffsetTopAndBottom(int offset, boolean requiresUpdate) {
mCircleView.bringToFront();
mCircleView.offsetTopAndBottom(offset);
mCurrentTargetOffsetTop = mCircleView.getTop();
if (requiresUpdate && android.os.Build.VERSION.SDK_INT < 11) {
invalidate();
}
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = MotionEventCompat.getActionIndex(ev);
final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);
}
}
/**
* Classes that wish to be notified when the swipe gesture correctly
* triggers a refresh should implement this interface.
*/
public interface OnRefreshListener {
public void onRefresh();
}
}
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