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：
