public class PickerView extends View
{
/**
* 传进来的·高度值,决定了绘制的字体大小,
*/
public static final String TAG = "PickerView";
/**
* text之间间距和minTextSize之比
*/
public static final float MARGIN_ALPHA = 3.5f;
/**
* 自动回滚到中间的速度
*/
public static final float SPEED = 3;
private List<String> mDataList;
/**
* 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 ;// 最大的字号
private float mMinTextSize ;// 最小的字号
private float mMaxTextAlpha = 250;
private float mMinTextAlpha = 100;
private int mColorText = 0x333333;
private int mViewHeight;
private int mViewWidth;
private float mLastDownX;
/**
* 滑动的距离
*/
private float mMoveLen = 0;
private boolean isInit = false;
private onSelectListener mSelectListener;
private Timer timer;
private MyTimerTask mTask;
private float baseline ;
Handler updateHandler = new Handler()
{
@Override
public void handleMessage(Message msg)
{
if (Math.abs(mMoveLen) < SPEED)
{
mMoveLen = 0;
if (mTask != null)
{
mTask.cancel();
mTask = null;
performSelect();//每次选择完成后,对接口方法里要传递的数据进行设置
}
} 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();
}
};
public PickerView(Context context)
{
super(context);
init();
}
public PickerView(Context context, AttributeSet attrs)
{
super(context, attrs);
init();
}
/**
* 暴露一个方法,让外界可以获得选中的值
* @param listener
*/
public void setOnSelectListener(onSelectListener listener)
{
mSelectListener = listener;
}
public String getSelect(){
return mDataList.get(mCurrentSelected);
}
private void performSelect()
{
if (mSelectListener != null)
mSelectListener.onSelect(mDataList.get(mCurrentSelected));
}
public void setData(List<String> datas)
{
mDataList = datas;
mCurrentSelected = 2;
invalidate();
}
public void setSelected(int selected)
{
mCurrentSelected = selected;
}
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();
// 按照View的高度计算字体大小
mMaxTextSize = mViewWidth / 12.0f-10;
mMinTextSize = mMaxTextSize / 2.0f;
isInit = true;
invalidate();
}
private void init()
{
timer = new Timer();
mDataList = new ArrayList<String>();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Paint.Style.FILL);
mPaint.setTextAlign(Paint.Align.CENTER);
mPaint.setColor(mColorText);
}
@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(mViewWidth / 2.0f, mMoveLen);
float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize+5;
// 设置字体的大小
mPaint.setTextSize(size);
// 设置字体的清晰度
mPaint.setColor(Color.rgb(208, 165, 59));
mPaint.setAntiAlias(true);
canvas.drawCircle(mViewWidth / 2.0f, mViewHeight / 2.0f, mViewHeight / 2.0f , mPaint);
mPaint.setAntiAlias(true);
mPaint.setColor(Color.rgb(243, 189, 21));
canvas.drawCircle(mViewWidth / 2.0f, mViewHeight / 2.0f, mViewHeight / 2.0f -2, mPaint);
mPaint.setColor(Color.rgb(255, 255, 255));
mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));// 设置字体的清晰度
// 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 y = (float) (mViewHeight / 2.0);
float x = (float) (mViewWidth / 2.0 + mMoveLen);
Paint.FontMetricsInt fmi = mPaint.getFontMetricsInt();
baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));
canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);
for (int i = 1; (mCurrentSelected - i) >= 0; i++)
{ //System.out.println(i);
//System.out.println("上");
drawOtherText(canvas, i, -1);
}
// 绘制下方data
for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)
{
//System.out.println("下");
drawOtherText(canvas, i, 1);
}
}
/**
* @param canvas
* @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)
{
//scale都为0
float d = (float) (MARGIN_ALPHA * mMinTextSize * position + type
* mMoveLen);
float scale = parabola(mViewWidth / 2.0f, d);
float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;
mPaint.setTextSize(size);
mPaint.setColor(Color.rgb(0,0,0));
mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale ));
float x = (float) (mViewWidth / 2.0 + type * (d+10));
//float y = (float)(mViewHeight / 2.0);
Paint.FontMetricsInt fmi = mPaint.getFontMetricsInt();
//System.out.println(fmi.toString());
//float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));
canvas.drawText(mDataList.get(mCurrentSelected + type * (position)),
x,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(event);
break;
}
return true;
}
private void doDown(MotionEvent event)
{
if (mTask != null)
{
mTask.cancel();
mTask = null;
}
mLastDownX = event.getX();
}
private void doMove(MotionEvent event)
{
//System.out.println("first:"+mMoveLen);
mMoveLen += (event.getX() - mLastDownX);
System.out.println("second:"+mMoveLen);
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;
}
mLastDownX = event.getX();
invalidate();
}
private void doUp(MotionEvent event)
{
// 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);
}
class MyTimerTask extends TimerTask
{
Handler handler;
public MyTimerTask(Handler handler)
{
this.handler = handler;
}
@Override
public void run()
{
handler.sendMessage(handler.obtainMessage());
}
}
public interface onSelectListener
{
void onSelect(String text);
}
}
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