android 滚轮刻度尺的实现
TanishaBran
9年前
来自： http://www.jcodecraeer.com//a/anzhuokaifa/androidkaifa/2014/0902/1671.html
卷尺，通过左右滑动来选择不同的刻度值。这方面的东西以前没弄过，以目前你的能力，想了几种思路都死在了半路上。比如上面的刻度线如何弄，滑动的时候又该如何弄；下面的数字又如何弄；看起来像圆圈的效果该如何弄。时间紧迫，就俩晚上的时间。没有好的思路就参考别人的先吧，说来也巧，两天前刚看过一个日期选择控件，还有以前看的一个仿IPhone滚动控件，效果类似：
本想找作者傲慢的上校交流下，但是时间比较紧，源码都给了也不是很好意思。大致的浏览了下，可能涉及下面几个东西：
1、背景：这个用shape实现。之前有研究过，也用过，但是还没实现过要求的效果；
2、刻度和数字：这个就不要乱想了，直接draw。相对来说还是比较简单的，就是画直线和数字；
3、滚动：滚动的时候不停的重绘实现一个滚动的效果。弄过，但是不确定实现的是啥样的效果；
4、快速滚动：Scroller和VelocityTracker可能是需要用到的东西。几乎完全没弄过，骚年，学习吧（需求的要求中，这个优先级可以最低）；
5、需求：刻度的单位是可以变的，比如十格一个单位，或者两格一个单位，在或者可以是任意的（这个前期思路没想好，实现起来就困难了，最后只弄了两种）。
其实，到了这一步基本上就已经可以实现了，看个最终效果先：
下面就一步一步来。在这之前还有个地方要说的，就是控件的接口：对外提供一个方法实现控件初始化和接收控件选择的值：显示的单位，最大值，最小值，当前值，回调接口。有了这些，先从最难的入手。首先，实现刻度和数字，并可以滑动。这个地方很关键，每个人有每个人的思路，而且思路的好坏直接影响到后面对不同单位的实现。目前的思路是根据当前显示的数值mValue，从控件中间向两边画刻度线，滑动的时候同时改变显示的值mValue，不足最小刻度的四舍五入：
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); drawScaleLine(canvas); // drawWheel(canvas); drawMiddleLine(canvas); } private void drawWheel(Canvas canvas) { Drawable wheel = getResources().getDrawable(R.drawable.bg_wheel); wheel.setBounds(0, 0, getWidth(), getHeight()); wheel.draw(canvas); } /** * 从中间往两边开始画刻度线 * * @param canvas */ private void drawScaleLine(Canvas canvas) { canvas.save(); Paint linePaint = new Paint(); linePaint.setStrokeWidth(2); linePaint.setColor(Color.BLACK); TextPaint textPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG); textPaint.setTextSize(TEXT_SIZE * mDensity); int width = mWidth, drawCount = 0; float xPosition = 0, textWidth = Layout.getDesiredWidth("0", textPaint); for (int i = 0; drawCount <= 4 * width; i++) { int numSize = String.valueOf(mValue + i).length(); xPosition = (width / 2 - mMove) + i * mLineDivider * mDensity; if (xPosition + getPaddingRight() < mWidth) { if ((mValue + i) % mModType == 0) { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MAX_HEIGHT, linePaint); if (mValue + i <= mMaxValue) { switch (mModType) { case MOD_TYPE_HALF: canvas.drawText(String.valueOf((mValue + i) / 2), countLeftStart(mValue + i, xPosition, textWidth), getHeight() - textWidth, textPaint); break; case MOD_TYPE_ONE: canvas.drawText(String.valueOf(mValue + i), xPosition - (textWidth * numSize / 2), getHeight() - textWidth, textPaint); break; default: break; } } } else { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MIN_HEIGHT, linePaint); } } xPosition = (width / 2 - mMove) - i * mLineDivider * mDensity; if (xPosition > getPaddingLeft()) { if ((mValue - i) % mModType == 0) { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MAX_HEIGHT, linePaint); if (mValue - i >= 0) { switch (mModType) { case MOD_TYPE_HALF: canvas.drawText(String.valueOf((mValue - i) / 2), countLeftStart(mValue - i, xPosition, textWidth), getHeight() - textWidth, textPaint); break; case MOD_TYPE_ONE: canvas.drawText(String.valueOf(mValue - i), xPosition - (textWidth * numSize / 2), getHeight() - textWidth, textPaint); break; default: break; } } } else { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MIN_HEIGHT, linePaint); } } drawCount += 2 * mLineDivider * mDensity; } canvas.restore(); } 接着就是滑动的加速问题，这里用到两个类Scroller和VelocityTracker，关于这两个类之后有机会会详细介绍，这里简单提下：VelocityTracker的作用是在用户加速滑动时计算该滑动多远，拿到这个之后通过Scroller来执行滑动过程的计算，最后是真实的“移动”――根据mValue的值进行重绘：
@Override public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); int xPosition = (int) event.getX(); if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); switch (action) { case MotionEvent.ACTION_DOWN: mScroller.forceFinished(true); mLastX = xPosition; mMove = 0; break; case MotionEvent.ACTION_MOVE: mMove += (mLastX - xPosition); changeMoveAndValue(); break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: countMoveEnd(); countVelocityTracker(event); return false; // break; default: break; } mLastX = xPosition; return true; } private void countVelocityTracker(MotionEvent event) { mVelocityTracker.computeCurrentVelocity(1000); float xVelocity = mVelocityTracker.getXVelocity(); if (Math.abs(xVelocity) > mMinVelocity) { mScroller.fling(0, 0, (int) xVelocity, 0, Integer.MIN_VALUE, Integer.MAX_VALUE, 0, 0); } } private void changeMoveAndValue() { int tValue = (int) (mMove / (mLineDivider * mDensity)); if (Math.abs(tValue) > 0) { mValue += tValue; mMove -= tValue * mLineDivider * mDensity; if (mValue <= 0 || mValue > mMaxValue) { mValue = mValue <= 0 ? 0 : mMaxValue; mMove = 0; mScroller.forceFinished(true); } notifyValueChange(); } postInvalidate(); } private void countMoveEnd() { int roundMove = Math.round(mMove / (mLineDivider * mDensity)); mValue = mValue + roundMove; mValue = mValue <= 0 ? 0 : mValue; mValue = mValue > mMaxValue ? mMaxValue : mValue; mLastX = 0; mMove = 0; notifyValueChange(); postInvalidate(); } private void notifyValueChange() { if (null != mListener) { if (mModType == MOD_TYPE_ONE) { mListener.onValueChange(mValue); } if (mModType == MOD_TYPE_HALF) { mListener.onValueChange(mValue / 2f); } } } @Override public void computeScroll() { super.computeScroll(); if (mScroller.computeScrollOffset()) { if (mScroller.getCurrX() == mScroller.getFinalX()) { // over countMoveEnd(); } else { int xPosition = mScroller.getCurrX(); mMove += (mLastX - xPosition); changeMoveAndValue(); mLastX = xPosition; } } } 最后就是圆圈背景的实现。这个用shape来做，可以使用setBackgroundDrawable()来做，也可以在draw中进行直接绘制，效果相同。其他的还有一些细节问题，比如滑动时刻度线超过边界，滑动距离大时候显示不完整等问题，这个只有做了才会发现。下面是shape背景的代码：
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" > <!-- two set color way --> <gradient android:angle="0" android:centerColor="#66FFFFFF" android:endColor="#66AAAAAA" android:startColor="#66AAAAAA" /> <corners android:radius="6dp" /> <stroke android:width="6dp" android:color="#FF666666" /> </shape>
用代码可以这样写：
private GradientDrawable createBackground() { float strokeWidth = 4 * mDensity; // 边框宽度 float roundRadius = 6 * mDensity; // 圆角半径 int strokeColor = Color.parseColor("#FF666666");// 边框颜色 // int fillColor = Color.parseColor("#DFDFE0");// 内部填充颜色 setPadding((int)strokeWidth, (int)strokeWidth, (int)strokeWidth, 0); int colors[] = { 0xFF999999, 0xFFFFFFFF, 0xFF999999 };// 分别为开始颜色，中间夜色，结束颜色 GradientDrawable bgDrawable = new GradientDrawable(GradientDrawable.Orientation.LEFT_RIGHT, colors);// 创建drawable // bgDrawable.setColor(fillColor); bgDrawable.setCornerRadius(roundRadius); bgDrawable.setStroke((int)strokeWidth, strokeColor); // setBackgroundDrawable(gd); return bgDrawable; } 最后在来贴一下完整的代码：
package com.ttdevs.wheel.widget; import android.annotation.SuppressLint; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.drawable.Drawable; import android.graphics.drawable.GradientDrawable; import android.text.Layout; import android.text.TextPaint; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.widget.Scroller; import com.ttdevs.wheel.R; /** * 卷尺控件类。由于时间比较紧，只有下班后有时间，因此只实现了基本功能。<br> * 细节问题包括滑动过程中widget边缘的刻度显示问题等<br> * * 周末有时间会继续更新<br> * * @author ttdevs * @version create：2014年8月26日 */ @SuppressLint("ClickableViewAccessibility") public class TuneWheel extends View { public interface OnValueChangeListener { public void onValueChange(float value); } public static final int MOD_TYPE_HALF = 2; public static final int MOD_TYPE_ONE = 10; private static final int ITEM_HALF_DIVIDER = 40; private static final int ITEM_ONE_DIVIDER = 10; private static final int ITEM_MAX_HEIGHT = 50; private static final int ITEM_MIN_HEIGHT = 20; private static final int TEXT_SIZE = 18; private float mDensity; private int mValue = 50, mMaxValue = 100, mModType = MOD_TYPE_HALF, mLineDivider = ITEM_HALF_DIVIDER; // private int mValue = 50, mMaxValue = 500, mModType = MOD_TYPE_ONE, // mLineDivider = ITEM_ONE_DIVIDER; private int mLastX, mMove; private int mWidth, mHeight; private int mMinVelocity; private Scroller mScroller; private VelocityTracker mVelocityTracker; private OnValueChangeListener mListener; @SuppressWarnings("deprecation") public TuneWheel(Context context, AttributeSet attrs) { super(context, attrs); mScroller = new Scroller(getContext()); mDensity = getContext().getResources().getDisplayMetrics().density; mMinVelocity = ViewConfiguration.get(getContext()).getScaledMinimumFlingVelocity(); // setBackgroundResource(R.drawable.bg_wheel); setBackgroundDrawable(createBackground()); } private GradientDrawable createBackground() { float strokeWidth = 4 * mDensity; // 边框宽度 float roundRadius = 6 * mDensity; // 圆角半径 int strokeColor = Color.parseColor("#FF666666");// 边框颜色 // int fillColor = Color.parseColor("#DFDFE0");// 内部填充颜色 setPadding((int)strokeWidth, (int)strokeWidth, (int)strokeWidth, 0); int colors[] = { 0xFF999999, 0xFFFFFFFF, 0xFF999999 };// 分别为开始颜色，中间夜色，结束颜色 GradientDrawable bgDrawable = new GradientDrawable(GradientDrawable.Orientation.LEFT_RIGHT, colors);// 创建drawable // bgDrawable.setColor(fillColor); bgDrawable.setCornerRadius(roundRadius); bgDrawable.setStroke((int)strokeWidth, strokeColor); // setBackgroundDrawable(gd); return bgDrawable; } /** * * 考虑可扩展，但是时间紧迫，只可以支持两种类型效果图中两种类型 * * @param value * 初始值 * @param maxValue * 最大值 * @param model * 刻度盘精度：<br> * {@link MOD_TYPE_HALF}<br> * {@link MOD_TYPE_ONE}<br> */ public void initViewParam(int defaultValue, int maxValue, int model) { switch (model) { case MOD_TYPE_HALF: mModType = MOD_TYPE_HALF; mLineDivider = ITEM_HALF_DIVIDER; mValue = defaultValue * 2; mMaxValue = maxValue * 2; break; case MOD_TYPE_ONE: mModType = MOD_TYPE_ONE; mLineDivider = ITEM_ONE_DIVIDER; mValue = defaultValue; mMaxValue = maxValue; break; default: break; } invalidate(); mLastX = 0; mMove = 0; notifyValueChange(); } /** * 设置用于接收结果的监听器 * * @param listener */ public void setValueChangeListener(OnValueChangeListener listener) { mListener = listener; } /** * 获取当前刻度值 * * @return */ public float getValue() { return mValue; } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { mWidth = getWidth(); mHeight = getHeight(); super.onLayout(changed, left, top, right, bottom); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); drawScaleLine(canvas); // drawWheel(canvas); drawMiddleLine(canvas); } private void drawWheel(Canvas canvas) { Drawable wheel = getResources().getDrawable(R.drawable.bg_wheel); wheel.setBounds(0, 0, getWidth(), getHeight()); wheel.draw(canvas); } /** * 从中间往两边开始画刻度线 * * @param canvas */ private void drawScaleLine(Canvas canvas) { canvas.save(); Paint linePaint = new Paint(); linePaint.setStrokeWidth(2); linePaint.setColor(Color.BLACK); TextPaint textPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG); textPaint.setTextSize(TEXT_SIZE * mDensity); int width = mWidth, drawCount = 0; float xPosition = 0, textWidth = Layout.getDesiredWidth("0", textPaint); for (int i = 0; drawCount <= 4 * width; i++) { int numSize = String.valueOf(mValue + i).length(); xPosition = (width / 2 - mMove) + i * mLineDivider * mDensity; if (xPosition + getPaddingRight() < mWidth) { if ((mValue + i) % mModType == 0) { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MAX_HEIGHT, linePaint); if (mValue + i <= mMaxValue) { switch (mModType) { case MOD_TYPE_HALF: canvas.drawText(String.valueOf((mValue + i) / 2), countLeftStart(mValue + i, xPosition, textWidth), getHeight() - textWidth, textPaint); break; case MOD_TYPE_ONE: canvas.drawText(String.valueOf(mValue + i), xPosition - (textWidth * numSize / 2), getHeight() - textWidth, textPaint); break; default: break; } } } else { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MIN_HEIGHT, linePaint); } } xPosition = (width / 2 - mMove) - i * mLineDivider * mDensity; if (xPosition > getPaddingLeft()) { if ((mValue - i) % mModType == 0) { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MAX_HEIGHT, linePaint); if (mValue - i >= 0) { switch (mModType) { case MOD_TYPE_HALF: canvas.drawText(String.valueOf((mValue - i) / 2), countLeftStart(mValue - i, xPosition, textWidth), getHeight() - textWidth, textPaint); break; case MOD_TYPE_ONE: canvas.drawText(String.valueOf(mValue - i), xPosition - (textWidth * numSize / 2), getHeight() - textWidth, textPaint); break; default: break; } } } else { canvas.drawLine(xPosition, getPaddingTop(), xPosition, mDensity * ITEM_MIN_HEIGHT, linePaint); } } drawCount += 2 * mLineDivider * mDensity; } canvas.restore(); } /** * 计算没有数字显示位置的辅助方法 * * @param value * @param xPosition * @param textWidth * @return */ private float countLeftStart(int value, float xPosition, float textWidth) { float xp = 0f; if (value < 20) { xp = xPosition - (textWidth * 1 / 2); } else { xp = xPosition - (textWidth * 2 / 2); } return xp; } /** * 画中间的红色指示线、阴影等。指示线两端简单的用了两个矩形代替 * * @param canvas */ private void drawMiddleLine(Canvas canvas) { // TOOD 常量太多，暂时放这，最终会放在类的开始，放远了怕很快忘记 int gap = 12, indexWidth = 8, indexTitleWidth = 24, indexTitleHight = 10, shadow = 6; String color = "#66999999"; canvas.save(); Paint redPaint = new Paint(); redPaint.setStrokeWidth(indexWidth); redPaint.setColor(Color.RED); canvas.drawLine(mWidth / 2, 0, mWidth / 2, mHeight, redPaint); Paint ovalPaint = new Paint(); ovalPaint.setColor(Color.RED); ovalPaint.setStrokeWidth(indexTitleWidth); canvas.drawLine(mWidth / 2, 0, mWidth / 2, indexTitleHight, ovalPaint); canvas.drawLine(mWidth / 2, mHeight - indexTitleHight, mWidth / 2, mHeight, ovalPaint); // RectF ovalRectF = new RectF(mWidth / 2 - 10, 0, mWidth / 2 + 10, 4 * // mDensity); //TODO 椭圆 // canvas.drawOval(ovalRectF, ovalPaint); // ovalRectF.set(mWidth / 2 - 10, mHeight - 8 * mDensity, mWidth / 2 + // 10, mHeight); //TODO Paint shadowPaint = new Paint(); shadowPaint.setStrokeWidth(shadow); shadowPaint.setColor(Color.parseColor(color)); canvas.drawLine(mWidth / 2 + gap, 0, mWidth / 2 + gap, mHeight, shadowPaint); canvas.restore(); } @Override public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); int xPosition = (int) event.getX(); if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); switch (action) { case MotionEvent.ACTION_DOWN: mScroller.forceFinished(true); mLastX = xPosition; mMove = 0; break; case MotionEvent.ACTION_MOVE: mMove += (mLastX - xPosition); changeMoveAndValue(); break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: countMoveEnd(); countVelocityTracker(event); return false; // break; default: break; } mLastX = xPosition; return true; } private void countVelocityTracker(MotionEvent event) { mVelocityTracker.computeCurrentVelocity(1000); float xVelocity = mVelocityTracker.getXVelocity(); if (Math.abs(xVelocity) > mMinVelocity) { mScroller.fling(0, 0, (int) xVelocity, 0, Integer.MIN_VALUE, Integer.MAX_VALUE, 0, 0); } } private void changeMoveAndValue() { int tValue = (int) (mMove / (mLineDivider * mDensity)); if (Math.abs(tValue) > 0) { mValue += tValue; mMove -= tValue * mLineDivider * mDensity; if (mValue <= 0 || mValue > mMaxValue) { mValue = mValue <= 0 ? 0 : mMaxValue; mMove = 0; mScroller.forceFinished(true); } notifyValueChange(); } postInvalidate(); } private void countMoveEnd() { int roundMove = Math.round(mMove / (mLineDivider * mDensity)); mValue = mValue + roundMove; mValue = mValue <= 0 ? 0 : mValue; mValue = mValue > mMaxValue ? mMaxValue : mValue; mLastX = 0; mMove = 0; notifyValueChange(); postInvalidate(); } private void notifyValueChange() { if (null != mListener) { if (mModType == MOD_TYPE_ONE) { mListener.onValueChange(mValue); } if (mModType == MOD_TYPE_HALF) { mListener.onValueChange(mValue / 2f); } } } @Override public void computeScroll() { super.computeScroll(); if (mScroller.computeScrollOffset()) { if (mScroller.getCurrX() == mScroller.getFinalX()) { // over countMoveEnd(); } else { int xPosition = mScroller.getCurrX(); mMove += (mLastX - xPosition); changeMoveAndValue(); mLastX = xPosition; } } } }