package com.example.healthembed.util; import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask; import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Align;
import android.graphics.Paint.FontMetricsInt;
import android.graphics.Paint.Style;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View; /**
* 滚动选择器
*
* @author chenjing
*
*/
public class PickerView extends View
{ public static final String TAG = "PickerView";
/**
* text之间间距和minTextSize之比
*/
public static final float MARGIN_ALPHA = 2.8f;
/**
* 自动回滚到中间的速度
*/
public static final float SPEED = 2; 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 = 80;
private float mMinTextSize = 40; private float mMaxTextAlpha = 255;
private float mMinTextAlpha = 120; private int mColorText = 0x333333; 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; 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();
}
} 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();//重绘
} }; public PickerView(Context context)
{
super(context);
init();
} public PickerView(Context context, AttributeSet attrs)
{
super(context, attrs);
init();
} public void setOnSelectListener(onSelectListener listener)
{
mSelectListener = listener;
} private void performSelect()
{
if (mSelectListener != null)
mSelectListener.onSelect(mDataList.get(mCurrentSelected));
//选中的位置，这个位置是mDataList的中心位置，一直不变
} public void setData(List<String> datas)
{
mDataList = datas;
mCurrentSelected = datas.size() / 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);
//Inserts the specified element at the specified position in this list (optional operation)
} @Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewHeight = getMeasuredHeight();
Log.e(TAG,String.valueOf(mViewHeight));
mViewWidth = getMeasuredWidth();
Log.e(TAG,String.valueOf(mViewWidth));
// 按照View的高度计算字体大小
mMaxTextSize = mViewWidth / 9.0f;
mMinTextSize = mMaxTextSize / 2f;
isInit = true;
invalidate();//调用invalidate()方法，请求重新draw()
} private void init()
{
timer = new Timer();
mDataList = new ArrayList<String>();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);//抗锯齿
mPaint.setStyle(Style.FILL);
mPaint.setTextAlign(Align.CENTER);//设置绘制文字的对齐方向
mPaint.setColor(mColorText);
}
public void initDataHigh() { for(int j = 0; j<35; j++) {
moveTailToHead();
} } public void initDataLow() { for(int j = 0; j<50; j++) {
moveTailToHead();
} } @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);
FontMetricsInt fmi = mPaint.getFontMetricsInt();
float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));
*/ float x = (float) (mViewWidth / 2.0+ mMoveLen);
float y = (float) (mViewHeight / 2.0 );
FontMetricsInt fmi = mPaint.getFontMetricsInt();
float baseline = (float) (x - (fmi.bottom+fmi.descent)/2);
canvas.drawText(mDataList.get(mCurrentSelected), baseline, y, mPaint);
// 绘制上方data
for (int i = 1; (mCurrentSelected - i) >= 0; i++)
{
drawOtherText(canvas, i, -1);
Log.e(TAG,String.valueOf(mCurrentSelected));
}
// 绘制下方data
for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)
{
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)
{
float d = (float) (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);*/
float x = (float) (mViewWidth/ 2.0 + type * d);
FontMetricsInt fmi = mPaint.getFontMetricsInt();
float baseline = (float) (x - (fmi.bottom+fmi.descent));
canvas.drawText(mDataList.get(mCurrentSelected + type * position),
baseline,(float) (mViewHeight / 2.0), 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));//x的y次方
return f < 0 ? 0 : f;
} @Override
public boolean onTouchEvent(MotionEvent event)
{
switch (event.getActionMasked())
{
case MotionEvent.ACTION_DOWN://表示用户开始触摸
doDown(event);
break;
case MotionEvent.ACTION_MOVE:
doMove(event);
break;
case MotionEvent.ACTION_UP://表示用户抬起了手指
doUp(event);
break;
}
return true;
} private void doDown(MotionEvent event)
{
if (mTask != null)
{
mTask.cancel();
mTask = null;
}
mLastDownY = event.getX();
} private void doMove(MotionEvent event)
{ mMoveLen += (event.getX() - mLastDownY); //mMoveLen为正为向下滑
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.getX();
invalidate();
} /*
task - task to be scheduled.
firstTime - First time at which task is to be executed.
period - time in milliseconds between successive task executions.
*/
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, 1000);
//第三个参数,第一次调用之后，从第二次开始每隔多长的时间调用一次 run() 方法
} 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);
}
}
/**
* 获得屏幕的高度
*/
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics outMetrics = new DisplayMetrics();
wm.getDefaultDisplay().getMetrics(outMetrics);
mScreenHeight = outMetrics.heightPixels;
Log.i("test",String.valueOf(mScreenHeight)); //2s 720
难点1：
字体随距离的渐变。可以看到，text随离中心位置的距离变化而变化，这里变化的是透明度alpha和字体大小TexSize，这两个值我都设置了Max和Min值，通过其与中心点的距离计算scale。
难点2：
循环滚动。为了解决循环滚动的问题我把存放text的List从中间往上下摊开，通过不断地moveHeadToTail和moveTailToHead使选中的text始终是list的中间position的值。
效果图：