背景:
項目要求寫一個選擇器:不僅僅是單純的時間,還包括自定義部分.
搜了很久,搜出來只用一個自定義view.java類,再簡單封裝下的選擇器:
貼下源碼:public class PickerView extends View{
public static final String TAG = "PickerView";
/**
* text之間間距和minTextSize之比
*/
public static final float MARGIN_ALPHA = 2.8f;
/**
* 自動回滾到中間的速度
*/
public static final float SPEED = 2;
private List mDataList;
/**
* 選中的位置，這個位置是mDataList的中心位置，一直不變
*/
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;
/**
* 滑動的距離
*/
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
// 這里mMoveLen / Math.abs(mMoveLen)是為了保有mMoveLen的正負號，以實現上滾或下滾
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();
}
public void setOnSelectListener(onSelectListener listener)
{
mSelectListener = listener;
}
private void performSelect()
{
if (mSelectListener != null)
mSelectListener.onSelect(mDataList.get(mCurrentSelected));
}
public void setData(List datas)
{
mDataList = datas;
mCurrentSelected = datas.size() / 2;
invalidate();
}
/**
* 選擇選中的item的index
*
* @param selected
*/
public void setSelected(int selected)
{
mCurrentSelected = selected;
int distance = mDataList.size() / 2 - mCurrentSelected;
if (distance < 0)
for (int i = 0; i < -distance; i++)
{
moveHeadToTail();
mCurrentSelected--;
}
else if (distance > 0)
for (int i = 0; i < distance; i++)
{
moveTailToHead();
mCurrentSelected++;
}
invalidate();
}
/**
* 選擇選中的內容
*
* @param mSelectItem
*/
public void setSelected(String mSelectItem)
{
for (int i = 0; i < mDataList.size(); i++)
if (mDataList.get(i).equals(mSelectItem))
{
setSelected(i);
break;
}
}
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的高度計算字體大小
mMaxTextSize = mViewHeight / 4.0f;
mMinTextSize = mMaxTextSize / 2f;
isInit = true;
invalidate();
}
private void init()
{
timer = new Timer();
mDataList = new ArrayList();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Style.FILL);
mPaint.setTextAlign(Align.CENTER);
mPaint.setColor(mColorText);
}
@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
// 根據index繪制view
if (isInit)
drawData(canvas);
}
private void drawData(Canvas canvas)
{
// 先繪制選中的text再往上往下繪制其余的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居中繪制，注意baseline的計算才能達到居中，y值是text中心坐標
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));
canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);
// 繪制上方data
for (int i = 1; (mCurrentSelected - i) >= 0; i++)
{
drawOtherText(canvas, i, -1);
}
// 繪制下方data
for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)
{
drawOtherText(canvas, i, 1);
}
}
/**
* @param canvas
* @param position
* 距離mCurrentSelected的差值
* @param type
* 1表示向下繪制，-1表示向上繪制
*/
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);
FontMetricsInt fmi = mPaint.getFontMetricsInt();
float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));
canvas.drawText(mDataList.get(mCurrentSelected + type * position),
(float) (mViewWidth / 2.0), baseline, mPaint);
}
/**
* 拋物線
*
* @param zero
* 零點坐標
* @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;
}
mLastDownY = event.getY();
}
private void doMove(MotionEvent event)
{
mMoveLen += (event.getY() - mLastDownY);
if (mMoveLen > MARGIN_ALPHA * mMinTextSize / 2)
{
// 往下滑超過離開距離
moveTailToHead();
mMoveLen = mMoveLen - MARGIN_ALPHA * mMinTextSize;
} else if (mMoveLen < -MARGIN_ALPHA * mMinTextSize / 2)
{
// 往上滑超過離開距離
moveHeadToTail();
mMoveLen = mMoveLen + MARGIN_ALPHA * mMinTextSize;
}
mLastDownY = event.getY();
invalidate();
}
private void doUp(MotionEvent event)
{
// 抬起手后mCurrentSelected的位置由當前位置move到中間選中位置
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);
}
}
`
這里定義的就是可以滾動的view,直接放入xml文件中即可
