上下滑动选择器
//同事的项目里搬来的砖哈哈.
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
public class PickerView extends View {
/**
* text之间间距和minTextSize之比
*/
public static final float MARGIN_ALPHA =2.5f;
/**
* 自动回滚到中间的速度
*/
public static final float SPEED =2;
private ListmDataList;
/**
* 默认初始化时选中的位置，这个位置是mDataList的中心位置，一直不变
*/
private int mCurrentSelected;
private Paint mPaint;
private float mMaxTextSize =20;
private float mMinTextSize =10;
private float mMaxTextAlpha =255;
private float mMinTextAlpha =120;
private int mViewHeight;
private int mViewWidth;
private float mLastDownY;
/**
* 滑动的距离
*/
private float mMoveLen =0;
private boolean isInit =false;
private onSelectListener mSelectListener;
private Timer timer;
private MyTimerTask mTask;
private Handler updateHandler =new Handler() {
@Override
public void handleMessage(Message msg) {
if (Math.abs(mMoveLen)
mMoveLen =0;
if (mTask !=null) {
mTask.cancel();
mTask =null;
performSelect();
}
}else {
// 这里mMoveLen / Math.abs(mMoveLen)是为了保有mMoveLen的正负号，以实现上滚或下滚
mMoveLen =mMoveLen -mMoveLen /Math.abs(mMoveLen) *SPEED;
invalidate();
}
}
};
//构造方法都调用init
public PickerView(Context context) {
super(context);
init();
}
public PickerView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
//以下为主要使用的public方法---------------------------------------------------------------------------------
/*
* 获取到当前选中的数据在数据集中的position
*/
public int getCurrentItem() {
return mCurrentSelected;
}
/*
* 设置监听,这个onSelectedLisener需要实现一个onSelect(String text)方法
* text是当前显示的数据
*/
public void setOnSelectListener(onSelectListener listener) {
mSelectListener = listener;
}
/*
* 设置数据集，参数类型为List
*/
public void setData(List datas) {
mDataList = datas;
mCurrentSelected = datas.size() /2;
invalidate();
}
/*
* 设置当前选中的数据
*/
public void setSelected(int selected) {
mCurrentSelected = selected;
}
//-------------------------------------------------------------------------------------
private void performSelect() {
if (mSelectListener !=null)
mSelectListener.onSelect(mDataList.get(mCurrentSelected));
}
private void moveHeadToTail() {
String head =mDataList.get(0);
mDataList.remove(0);
mDataList.add(head);
}
private void moveTailToHead() {
String tail =mDataList.get(mDataList.size() -1);
mDataList.remove(mDataList.size() -1);
mDataList.add(0, tail);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewHeight = getMeasuredHeight();
mViewWidth = getMeasuredWidth();
Log.i("chairs", "mViewHeight " +mViewHeight);
Log.i("chairs", "mViewWidth " +mViewWidth);
// 按照View的高度计算字体大小
mMaxTextSize =mViewHeight /8.0f;
mMinTextSize =mMaxTextSize /1.5f;
isInit =true;
invalidate();
}
private void init() {
timer =new Timer();
mDataList =new ArrayList<>();
mPaint =new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Paint.Style.FILL);
mPaint.setTextAlign(Paint.Align.CENTER);
mPaint.setColor(0x333333);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// 根据index绘制view
if (isInit)
drawData(canvas);
}
private void drawData(Canvas canvas) {
// 先绘制选中的text再往上往下绘制其余的text
float scale = parabola(mViewHeight /4.0f, mMoveLen);
float size = (mMaxTextSize -mMinTextSize) *scale +mMinTextSize;
mPaint.setTextSize(size);
mPaint.setAlpha((int) ((mMaxTextAlpha -mMinTextAlpha) *scale +mMinTextAlpha));
// text居中绘制，注意baseline的计算才能达到居中，y值是text中心坐标
float x = (float) (mViewWidth /2.0);
float y = (float) (mViewHeight /2.0 +mMoveLen);
Paint.FontMetricsInt fmi =mPaint.getFontMetricsInt();
float baseline = (float) (y - (fmi.bottom /2.0 +fmi.top /2.0));
canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);
Paint linePaint =new Paint();
linePaint.setColor(Color.LTGRAY);
linePaint.setStrokeWidth(3);
// 绘制上方data
for (int i =1; (mCurrentSelected -i) >=0; i++) {
drawOtherText(canvas, i, -1);
}
// 绘制下方data
for (int i =1; (mCurrentSelected +i)
drawOtherText(canvas, i, 1);
}
}
/**
* @param position 距离mCurrentSelected的差值
* @param type 1表示向下绘制，-1表示向上绘制
*/
private void drawOtherText(Canvas canvas, int position, int type) {
float d =MARGIN_ALPHA *mMinTextSize * position + type
*mMoveLen;
float scale = parabola(mViewHeight /4.0f, d);
float size = (mMaxTextSize -mMinTextSize) *scale +mMinTextSize;
mPaint.setTextSize(size);
mPaint.setAlpha((int) ((mMaxTextAlpha -mMinTextAlpha) *scale +mMinTextAlpha));
float y = (float) (mViewHeight /2.0 + type *d);
Paint.FontMetricsInt fmi =mPaint.getFontMetricsInt();
float baseline = (float) (y - (fmi.bottom /2.0 +fmi.top /2.0));
canvas.drawText(mDataList.get(mCurrentSelected + type * position),
mViewWidth /2f, baseline, mPaint);
}
/**
* 抛物线
*
* @param zero 零点坐标
* @param x 偏移量
* @return scale
*/
private float parabola(float zero, float x) {
float f = (float) (1 -Math.pow(x / zero, 2));
return f <0 ?0 :f;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
doDown(event);
break;
case MotionEvent.ACTION_MOVE:
doMove(event);
break;
case MotionEvent.ACTION_UP:
doUp();
break;
}
return true;
}
private void doDown(MotionEvent event) {
if (mTask !=null) {
mTask.cancel();
mTask =null;
}
mLastDownY = event.getY();
}
private void doMove(MotionEvent event) {
mMoveLen += (event.getY() -mLastDownY);
if (mMoveLen >MARGIN_ALPHA *mMinTextSize /2) {
// 往下滑超过离开距离
moveTailToHead();
mMoveLen =mMoveLen -MARGIN_ALPHA *mMinTextSize;
}else if (mMoveLen < -MARGIN_ALPHA *mMinTextSize /2) {
// 往上滑超过离开距离
moveHeadToTail();
mMoveLen =mMoveLen +MARGIN_ALPHA *mMinTextSize;
}
mLastDownY = event.getY();
invalidate();
}
private void doUp() {
// 抬起手后mCurrentSelected的位置由当前位置move到中间选中位置
if (Math.abs(mMoveLen) <0.0001) {
mMoveLen =0;
return;
}
if (mTask !=null) {
mTask.cancel();
mTask =null;
}
mTask =new MyTimerTask(updateHandler);
timer.schedule(mTask, 0, 10);
}
private class MyTimerTask extends TimerTask {
Handler handler;
private MyTimerTask(Handler handler) {
this.handler = handler;
}
@Override
public void run() {
handler.sendMessage(handler.obtainMessage());
}
}
public interface onSelectListener {
void onSelect(String text);
}
}
