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/**
* 滾輪視圖，可設(shè)置是否循環(huán)模式，實(shí)現(xiàn)OnScrollChangedListener接口以監(jiān)聽滾輪變化
* Created by huzn on 2016/10/27.
*/
public class EasyPickerView extends View {
// 文字大小
private int textSize;
// 顏色，默認(rèn)Color.BLACK
private int textColor;
// 文字之間的間隔，默認(rèn)10dp
private int textPadding;
// 文字最大放大比例，默認(rèn)2.0f
private float textMaxScale;
// 文字最小alpha值，范圍0.0f~1.0f，默認(rèn)0.4f
private float textMinAlpha;
// 是否循環(huán)模式，默認(rèn)是
private boolean isRecycleMode;
// 正常狀態(tài)下最多顯示幾個文字，默認(rèn)3（偶數(shù)時，邊緣的文字會截斷）
private int maxShowNum;
private TextPaint textPaint;
private Paint.FontMetrics fm;
private Scroller scroller;
private VelocityTracker velocityTracker;
private int minimumVelocity;
private int maximumVelocity;
private int scaledTouchSlop;
// 數(shù)據(jù)
private ArrayList<String> dataList = new ArrayList<>();
// 中間x坐標(biāo)
private int cx;
// 中間y坐標(biāo)
private int cy;
// 文字最大寬度
private float maxTextWidth;
// 文字高度
private int textHeight;
// 實(shí)際內(nèi)容寬度
private int contentWidth;
// 實(shí)際內(nèi)容高度
private int contentHeight;
// 按下時的y坐標(biāo)
private float downY;
// 本次滑動的y坐標(biāo)偏移值
private float offsetY;
// 在fling之前的offsetY
private float oldOffsetY;
// 當(dāng)前選中項(xiàng)
private int curIndex;
private int offsetIndex;
// 回彈距離
private float bounceDistance;
// 是否正處于滑動狀態(tài)
private boolean isSliding = false;
public EasyPickerView(Context context) {
this(context, null);
}
public EasyPickerView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public EasyPickerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.EasyPickerView, defStyleAttr, 0);
textSize = a.getDimensionPixelSize(R.styleable.EasyPickerView_epvTextSize, (int) TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
textColor = a.getColor(R.styleable.EasyPickerView_epvTextColor, Color.BLACK);
textPadding = a.getDimensionPixelSize(R.styleable.EasyPickerView_epvTextPadding, (int) TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_DIP, 20, getResources().getDisplayMetrics()));
textMaxScale = a.getFloat(R.styleable.EasyPickerView_epvTextMaxScale, 2.0f);
textMinAlpha = a.getFloat(R.styleable.EasyPickerView_epvTextMinAlpha, 0.4f);
isRecycleMode = a.getBoolean(R.styleable.EasyPickerView_epvRecycleMode, true);
maxShowNum = a.getInteger(R.styleable.EasyPickerView_epvMaxShowNum, 3);
a.recycle();
textPaint = new TextPaint();
textPaint.setColor(textColor);
textPaint.setTextSize(textSize);
textPaint.setAntiAlias(true);
fm = textPaint.getFontMetrics();
textHeight = (int) (fm.bottom - fm.top);
scroller = new Scroller(context);
minimumVelocity = ViewConfiguration.get(getContext()).getScaledMinimumFlingVelocity();
maximumVelocity = ViewConfiguration.get(getContext()).getScaledMaximumFlingVelocity();
scaledTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int mode = MeasureSpec.getMode(widthMeasureSpec);
int width = MeasureSpec.getSize(widthMeasureSpec);
contentWidth = (int) (maxTextWidth * textMaxScale + getPaddingLeft() + getPaddingRight());
if (mode != MeasureSpec.EXACTLY) { // wrap_content
width = contentWidth;
}
mode = MeasureSpec.getMode(heightMeasureSpec);
int height = MeasureSpec.getSize(heightMeasureSpec);
contentHeight = textHeight * maxShowNum + textPadding * maxShowNum;
if (mode != MeasureSpec.EXACTLY) { // wrap_content
height = contentHeight + getPaddingTop() + getPaddingBottom();
}
cx = width / 2;
cy = height / 2;
setMeasuredDimension(width, height);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
getParent().requestDisallowInterceptTouchEvent(true);
return super.dispatchTouchEvent(event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
addVelocityTracker(event);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (!scroller.isFinished()) {
scroller.forceFinished(true);
finishScroll();
}
downY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
offsetY = event.getY() - downY;
if (isSliding || Math.abs(offsetY) > scaledTouchSlop) {
isSliding = true;
reDraw();
}
break;
case MotionEvent.ACTION_UP:
int scrollYVelocity = 2 * getScrollYVelocity() / 3;
if (Math.abs(scrollYVelocity) > minimumVelocity) {
oldOffsetY = offsetY;
scroller.fling(0, 0, 0, scrollYVelocity, 0, 0, -Integer.MAX_VALUE, Integer.MAX_VALUE);
invalidate();
} else {
finishScroll();
}
// 沒有滑動，則判斷點(diǎn)擊事件
if (!isSliding) {
if (downY < contentHeight / 3)
moveBy(-1);
else if (downY > 2 * contentHeight / 3)
moveBy(1);
}
isSliding = false;
recycleVelocityTracker();
break;
}
return true;
}
@Override
protected void onDraw(Canvas canvas) {
if (null != dataList && dataList.size() > 0) {
canvas.clipRect(
cx - contentWidth / 2,
cy - contentHeight / 2,
cx + contentWidth / 2,
cy + contentHeight / 2
);
// 繪制文字，從當(dāng)前中間項(xiàng)往前、后一共繪制maxShowNum個字
int size = dataList.size();
int centerPadding = textHeight + textPadding;
int half = maxShowNum / 2 + 1;
for (int i = -half; i <= half; i++) {
int index = curIndex - offsetIndex + i;
if (isRecycleMode) {
if (index < 0)
index = (index + 1) % dataList.size() + dataList.size() - 1;
else if (index > dataList.size() - 1)
index = index % dataList.size();
}
if (index >= 0 && index < size) {
// 計算每個字的中間y坐標(biāo)
int tempY = cy + i * centerPadding;
tempY += offsetY % centerPadding;
// 根據(jù)每個字中間y坐標(biāo)到cy的距離，計算出scale值
float scale = 1.0f - (1.0f * Math.abs(tempY - cy) / centerPadding);
// 根據(jù)textMaxScale，計算出tempScale值，即實(shí)際text應(yīng)該放大的倍數(shù)，范圍 1~textMaxScale
float tempScale = scale * (textMaxScale - 1.0f) + 1.0f;
tempScale = tempScale < 1.0f ? 1.0f : tempScale;
// 計算文字alpha值
float textAlpha = textMinAlpha;
if (textMaxScale != 1) {
float tempAlpha = (tempScale - 1) / (textMaxScale - 1);
textAlpha = (1 - textMinAlpha) * tempAlpha + textMinAlpha;
}
textPaint.setTextSize(textSize * tempScale);
textPaint.setAlpha((int) (255 * textAlpha));
// 繪制
Paint.FontMetrics tempFm = textPaint.getFontMetrics();
String text = dataList.get(index);
float textWidth = textPaint.measureText(text);
canvas.drawText(text, cx - textWidth / 2, tempY - (tempFm.ascent + tempFm.descent) / 2, textPaint);
}
}
}
}
@Override
public void computeScroll() {
if (scroller.computeScrollOffset()) {
offsetY = oldOffsetY + scroller.getCurrY();
if (!scroller.isFinished())
reDraw();
else
finishScroll();
}
}
private void addVelocityTracker(MotionEvent event) {
if (velocityTracker == null)
velocityTracker = VelocityTracker.obtain();
velocityTracker.addMovement(event);
}
private void recycleVelocityTracker() {
if (velocityTracker != null) {
velocityTracker.recycle();
velocityTracker = null;
}
}
private int getScrollYVelocity() {
velocityTracker.computeCurrentVelocity(1000, maximumVelocity);
int velocity = (int) velocityTracker.getYVelocity();
return velocity;
}
private void reDraw() {
// curIndex需要偏移的量
int i = (int) (offsetY / (textHeight + textPadding));
if (isRecycleMode || (curIndex - i >= 0 && curIndex - i < dataList.size())) {
if (offsetIndex != i) {
offsetIndex = i;
if (null != onScrollChangedListener)
onScrollChangedListener.onScrollChanged(getNowIndex(-offsetIndex));
}
postInvalidate();
} else {
finishScroll();
}
}
private void finishScroll() {
// 判斷結(jié)束滑動后應(yīng)該停留在哪個位置
int centerPadding = textHeight + textPadding;
float v = offsetY % centerPadding;
if (v > 0.5f * centerPadding)
++offsetIndex;
else if (v < -0.5f * centerPadding)
--offsetIndex;
// 重置curIndex
curIndex = getNowIndex(-offsetIndex);
// 計算回彈的距離
bounceDistance = offsetIndex * centerPadding - offsetY;
offsetY += bounceDistance;
// 更新
if (null != onScrollChangedListener)
onScrollChangedListener.onScrollFinished(curIndex);
// 重繪
reset();
postInvalidate();
}
private int getNowIndex(int offsetIndex) {
int index = curIndex + offsetIndex;
if (isRecycleMode) {
if (index < 0)
index = (index + 1) % dataList.size() + dataList.size() - 1;
else if (index > dataList.size() - 1)
index = index % dataList.size();
} else {
if (index < 0)
index = 0;
else if (index > dataList.size() - 1)
index = dataList.size() - 1;
}
return index;
}
private void reset() {
offsetY = 0;
oldOffsetY = 0;
offsetIndex = 0;
bounceDistance = 0;
}
/**
* 設(shè)置要顯示的數(shù)據(jù)
*
* @param dataList 要顯示的數(shù)據(jù)
*/
public void setDataList(ArrayList<String> dataList) {
this.dataList.clear();
this.dataList.addAll(dataList);
// 更新maxTextWidth
if (null != dataList && dataList.size() > 0) {
int size = dataList.size();
for (int i = 0; i < size; i++) {
float tempWidth = textPaint.measureText(dataList.get(i));
if (tempWidth > maxTextWidth)
maxTextWidth = tempWidth;
}
curIndex = 0;
}
requestLayout();
invalidate();
}
/**
* 獲取當(dāng)前狀態(tài)下，選中的下標(biāo)
*
* @return 選中的下標(biāo)
*/
public int getCurIndex() {
return getNowIndex(-offsetIndex);
}
/**
* 滾動到指定位置
*
* @param index 需要滾動到的指定位置
*/
public void moveTo(int index) {
if (index < 0 || index >= dataList.size() || curIndex == index)
return;
if (!scroller.isFinished())
scroller.forceFinished(true);
finishScroll();
int dy = 0;
int centerPadding = textHeight + textPadding;
if (!isRecycleMode) {
dy = (curIndex - index) * centerPadding;
} else {
int offsetIndex = curIndex - index;
int d1 = Math.abs(offsetIndex) * centerPadding;
int d2 = (dataList.size() - Math.abs(offsetIndex)) * centerPadding;
if (offsetIndex > 0) {
if (d1 < d2)
dy = d1; // ascent
else
dy = -d2; // descent
} else {
if (d1 < d2)
dy = -d1; // descent
else
dy = d2; // ascent
}
}
scroller.startScroll(0, 0, 0, dy, 500);
invalidate();
}
/**
* 滾動指定的偏移量
*
* @param offsetIndex 指定的偏移量
*/
public void moveBy(int offsetIndex) {
moveTo(getNowIndex(offsetIndex));
}
/**
* 滾動發(fā)生變化時的回調(diào)接口
*/
public interface OnScrollChangedListener {
public void onScrollChanged(int curIndex);
public void onScrollFinished(int curIndex);
}
private OnScrollChangedListener onScrollChangedListener;
public void setOnScrollChangedListener(OnScrollChangedListener onScrollChangedListener) {
this.onScrollChangedListener = onScrollChangedListener;
}
}
