Android实现可左右滑动的选择控件

最近公司项目需求里有一个左右滑动的时间选择器，因为当时时间充裕就动手写了一个，这里把轮子贡献出来，大家有相似的需求可以用上



功能大致就是：可左右滑动，单选，滑动松开手后依靠滑动时的惯性继续向前滑动一段距离，并且当停止后自动回弹到只显示三个的状态，点左右两个三角号可向左右滑动一个

下面会贴上主要的代码

下载完整代码在后面有链接

public class SelectorView extends ViewGroup {

private static final String TAG = "SelectorView";

private int columnSpace;
private int childWidth;

private int touchSlop;

private CycleStruct<Integer> cycleStruct;

private VelocityTracker mVelocityTracker;
private Scroller mScroller;
private ValueAnimator mValueAnimator;

private int miniVelocity;
private SeletcorAdapter adapter;
private OnItemCheckListener mOnItemCheckListener;

private Checkable lastCheckedItem;
private int lastCheckedPosition = 0;

private int x_scroll = 0;
private float touchDownX;
private int x_down;
private int lastFillingX;
private boolean mScrolling;

public SelectorView(Context context) {
super(context);
}

public SelectorView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context,attrs);
}

private void init(Context context,AttributeSet attrs){
TypedArray t = context.obtainStyledAttributes(attrs, R.styleable.SelectorView);
columnSpace = t.getDimensionPixelSize(R.styleable.SelectorView_space,0);
t.recycle();

ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
touchSlop = viewConfiguration.getScaledTouchSlop();
miniVelocity = viewConfiguration.getScaledMinimumFlingVelocity();

mVelocityTracker = VelocityTracker.obtain();
mScroller = new Scroller(context);

mValueAnimator = new ValueAnimator();
mValueAnimator.setInterpolator(new AccelerateInterpolator());
mValueAnimator.addUpdateListener(mAnimatorUpdateListener);

cycleStruct = new CycleStruct<>();
cycleStruct.addData(0);
cycleStruct.addData(1);
cycleStruct.addData(2);
cycleStruct.addData(3);

}

private OnClickListener clickListener = new OnClickListener() {
@Override
public void onClick(View v) {
if(v.getTag()==null){
return;
}
Checkable checkable = (Checkable) v;
if(!checkable.isChecked()){
lastCheckedPosition = (int) v.getTag();
checkable.setChecked(true);
if(lastCheckedItem!=null&&lastCheckedItem!=v){
lastCheckedItem.setChecked(false);
}
lastCheckedItem = checkable;
}
if(mOnItemCheckListener!=null){
mOnItemCheckListener.onItemChecked(lastCheckedPosition);
}
}
};

@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
for (int i = 0; i < 4; i++) {
getChildAt(i).setOnClickListener(clickListener);
}
}

private int getMaxScrollRange(){
if(adapter!=null&&adapter.getItemCount()>3){
return (adapter.getItemCount()-3)*(childWidth+columnSpace);
}
return 0;
}

private int getItemWidth(){
return childWidth+columnSpace;
}
private int lastStartIndex = -1;
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int measureHeight = getChildAt(0).getMeasuredHeight();
int measureWidth = getChildAt(0).getMeasuredWidth();
childWidth = measureWidth;
//edge check
if(x_scroll> getMaxScrollRange()){
x_scroll = getMaxScrollRange();
}else if(x_scroll<0){
x_scroll = 0;
}

int startIndex = x_scroll/getItemWidth();
cycleStruct.start(startIndex);
int offset = x_scroll%getItemWidth();
int itemStartPos = getItemWidth()*2+offset;
int childOrder = 0;
while (cycleStruct.canNext()){
int i = cycleStruct.get();
View child = getChildAt(i);
int itemIndex = startIndex+childOrder;
//scrolled by an item,order has changed,set value again
if(adapter!=null&&itemIndex<adapter.getItemCount()&&(lastStartIndex!=startIndex)){
adapter.setView(child,itemIndex);
child.setTag(itemIndex);
Checkable checkable = (Checkable) child;
checkable.setChecked(lastCheckedPosition==itemIndex);
if(lastCheckedPosition==itemIndex){
//set lastCheckedItem when init
lastCheckedItem = checkable;
}
//notify scrolled
if(mOnItemCheckListener!=null&&childOrder==0){
mOnItemCheckListener.onScrolled(itemIndex);
}
}
child.layout(itemStartPos+columnSpace/2,0,itemStartPos+columnSpace/2+measureWidth,measureHeight);
itemStartPos -= getItemWidth();
childOrder ++;
}
lastStartIndex = startIndex;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int width = MeasureSpec.getSize(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);

View child = getChildAt(0);
LayoutParams layoutParam = child.getLayoutParams();
int childWidth = (width - 3* columnSpace)/3;
int childHeightSpec;
if(layoutParam == null||layoutParam.height==LayoutParams.WRAP_CONTENT){
childHeightSpec = MeasureSpec.makeMeasureSpec(heightSize,MeasureSpec.AT_MOST);
}else if(layoutParam.height==LayoutParams.MATCH_PARENT){
childHeightSpec = MeasureSpec.makeMeasureSpec(heightSize,MeasureSpec.EXACTLY);
}else{//指定高度
childHeightSpec = MeasureSpec.makeMeasureSpec(layoutParam.height,MeasureSpec.EXACTLY);
}
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
View v = getChildAt(i);
v.measure(MeasureSpec.makeMeasureSpec(childWidth,MeasureSpec.EXACTLY),childHeightSpec);
}
int childHeight = child.getMeasuredHeight();
//the view height equals it's child height
setMeasuredDimension(width,childHeight);
}

@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
cancelAnimation();
touchDownX = event.getX();
x_down = x_scroll;
mScrolling = false;
break;
case MotionEvent.ACTION_MOVE:
if (Math.abs(touchDownX - event.getX()) >=touchSlop) {
mScrolling = true;
} else {
mScrolling = false;
}
break;
case MotionEvent.ACTION_UP:
mScrolling = false;
break;
}
return mScrolling;
}

int startFilingX;
@Override
public boolean onTouchEvent(MotionEvent event) {
mVelocityTracker.addMovement(event);
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
float offsetX = event.getX()- touchDownX;
if(mScrolling||Math.abs(offsetX)>touchSlop){
mScrolling= true;
x_scroll = (int) (x_down+offsetX);
requestLayout();
}
break;
case MotionEvent.ACTION_UP:
mScrolling = false;
mVelocityTracker.computeCurrentVelocity(1000);
if(Math.abs(mVelocityTracker.getXVelocity())>miniVelocity){
startFilingX = x_scroll;
mScroller.fling(0,0, (int) mVelocityTracker.getXVelocity(),0,Integer.MIN_VALUE,Integer.MAX_VALUE,0,0);
invalidate();
Log.i(TAG, "onTouchEvent: filing");
}else{
Log.i(TAG, "onTouchEvent: not filing");
regressPos();
}

break;
}
return true;
}

@Override
public void computeScroll() {
if(mScroller.computeScrollOffset()&&mScroller.getCurrX()!=lastFillingX&&mScroller.getCurrX()!=0){
x_scroll = startFilingX+mScroller.getCurrX();
lastFillingX = mScroller.getCurrX();
Log.i(TAG, "computeScroll: filling:"+mScroller.getCurrX());
requestLayout();
}else if((!mScrolling)&&(!mValueAnimator.isStarted())&&(x_scroll%getItemWidth()!=0)){
regressPos();
Log.i(TAG, "computeScroll: regress");
}else{
Log.i(TAG, "computeScroll: none");
}

}

private void cancelAnimation(){
mValueAnimator.cancel();
mScroller.abortAnimation();
}

/**
* 弹回到只显示三个的位置
*/
private void regressPos(){
int residue = x_scroll%getItemWidth();
int animStep;
if(residue>getItemWidth()/2){
animStep = getItemWidth()-residue;
}else{
animStep = -residue;
}
if(mValueAnimator.isRunning()){
mValueAnimator.cancel();
}
Log.i(TAG, "regressPos: x_scroll:"+x_scroll+",to:"+(x_scroll+animStep));
mValueAnimator.setIntValues(x_scroll,x_scroll+animStep);
mValueAnimator.setDuration(Math.abs(animStep)/3);
mValueAnimator.start();
}

private ValueAnimator.AnimatorUpdateListener mAnimatorUpdateListener = new ValueAnimator.AnimatorUpdateListener(){
@Override
public void onAnimationUpdate(ValueAnimator animation) {
x_scroll = (int) animation.getAnimatedValue();
Log.i(TAG, "onAnimationUpdate: x_scroll:"+x_scroll);
requestLayout();
}
};

public void setAdapter(SeletcorAdapter adapter){
this.adapter = adapter;
requestLayout();
}

public void setOnItemCheckListener(OnItemCheckListener l){
mOnItemCheckListener = l;
}

public abstract static class SeletcorAdapter{
public abstract int getItemCount();
public abstract void setView(View view,int position);
}

public interface OnItemCheckListener{
void onItemChecked(int position);
void onScrolled(int position);
}

public void left(){
mValueAnimator.cancel();
Log.i(TAG, "left: x_scroll:"+x_scroll+",max:"+ getMaxScrollRange());
if(x_scroll< getMaxScrollRange()){
int to = x_scroll+getItemWidth();
if(to > getMaxScrollRange()){
to = getMaxScrollRange();
}
Log.i(TAG, "left: from:"+x_scroll+",to:"+to);
mValueAnimator.setIntValues(x_scroll,to);
mValueAnimator.setDuration(Math.abs(getItemWidth())/3);
mValueAnimator.start();
}
}

public void right(){
mValueAnimator.cancel();
if(x_scroll>0){
int to = x_scroll - getItemWidth();
if(to<0){
to = 0;
}
mValueAnimator.setIntValues(x_scroll,to);
mValueAnimator.setDuration(Math.abs(getItemWidth())/3);
mValueAnimator.start();
}
}
}

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