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package xxx.xxx.xxx.xxx.xxx;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.Scroller;
import com.txh.yunyao.R;
import java.util.ArrayList;
import java.util.List;
/**
* 滚轮视图，可设置是否循环模式，实现OnScrollChangedListener接口以监听滚轮变化
*/
public class EasyPickerView extends View {
// 文字大小
private int textSize;
// 颜色，默认Color.BLACK
private int textColor;
// 文字之间的间隔，默认10dp
private int textPadding;
// 文字最大放大比例，默认2.0f
private float textMaxScale;
// 文字最小alpha值，范围0.0f~1.0f，默认0.4f
private float textMinAlpha;
// 是否循环模式，默认是
private boolean isRecycleMode;
// 正常状态下最多显示几个文字，默认3（偶数时，边缘的文字会截断）
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;
// 数据
private List<String> dataList = new ArrayList<>(0);
// 中间x坐标
private int cx;
// 中间y坐标
private int cy;
// 文字最大宽度
private float maxTextWidth;
// 文字高度
private int textHeight;
// 实际内容宽度
private int contentWidth;
// 实际内容高度
private int contentHeight;
// 按下时的y坐标
private float downY;
// 本次滑动的y坐标偏移值
private float offsetY;
// 在fling之前的offsetY
private float oldOffsetY;
// 当前选中项
private int curIndex;
private int offsetIndex;
// 回弹距离
private float bounceDistance;
// 是否正处于滑动状态
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();
}
// 没有滑动，则判断点击事件
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
);
// 绘制文字，从当前中间项往前、后一共绘制maxShowNum个字
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) {
// 计算每个字的中间y坐标
int tempY = cy + i * centerPadding;
tempY += offsetY % centerPadding;
// 根据每个字中间y坐标到cy的距离，计算出scale值
float scale = 1.0f - (1.0f * Math.abs(tempY - cy) / centerPadding);
// 根据textMaxScale，计算出tempScale值，即实际text应该放大的倍数，范围 1~textMaxScale
float tempScale = scale * (textMaxScale - 1.0f) + 1.0f;
tempScale = tempScale < 1.0f ? 1.0f : tempScale;
// 计算文字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));
// 绘制
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() {
// 判断结束滑动后应该停留在哪个位置
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);
// 计算回弹的距离
bounceDistance = offsetIndex * centerPadding - offsetY;
offsetY += bounceDistance;
// 更新
if (null != onScrollChangedListener)
onScrollChangedListener.onScrollFinished(curIndex);
// 重绘
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;
}
/**
* 设置要显示的数据
*
* @param dataList 要显示的数据
*/
public void setDataList(List<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();
}
/**
* 获取当前状态下，选中的下标
*
* @return 选中的下标
*/
public int getCurIndex() {
return getNowIndex(-offsetIndex);
}
/**
* 滚动到指定位置
*
* @param index 需要滚动到的指定位置
*/
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();
}
/**
* 滚动指定的偏移量
*
* @param offsetIndex 指定的偏移量
*/
public void moveBy(int offsetIndex) {
moveTo(getNowIndex(offsetIndex));
}
/**
* 滚动发生变化时的回调接口
*/
public interface OnScrollChangedListener {
public void onScrollChanged(int curIndex);
public void onScrollFinished(int curIndex);
}
private OnScrollChangedListener onScrollChangedListener;
public void setOnScrollChangedListener(OnScrollChangedListener onScrollChangedListener) {
this.onScrollChangedListener = onScrollChangedListener;
}
}
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