由于项目需要，设计了一个可以正负滑动的seekbar，满足获取正负数值的需要
/**
* 从中间可以向两边滑动 左负右正
* <p>
* Created by zhangjian on 2019/10/15 09:33
*/
public class CenterSeekBarView extends View {
private static final int DEFAULT_TOUCH_TARGET_SIZE = 100;
private final Paint paint;
private float minUnit = 0.1f;
private int coefficient = 10;//增加的系数
private boolean canMove = false;
private float width = 400; // need <= getWidth()
/**
* progress start max
*/
private int minProgress = 0;
/**
* progress end max
*/
private int maxProgress = 100;
/**
* 进度条的颜色 底色 背景色
*/
@ColorInt
private int progressBackColor;
/**
* 进度条的颜色
*/
@ColorInt
private int progressColor;
/**
* current progress
*/
private int progress = 0;
/**
* seekBar Thumb normal radius
*/
private float mThumbRadius = 20;
private float progressPosition;
private boolean isTouchLegal = false;
private RectF mBackRectF, mProgressRectF;
private int mThumbDrawColor;
private OnSeekBarChangeListener mOnSeekBarChangeListener;
public CenterSeekBarView(Context context) {
this(context, null);
}
public CenterSeekBarView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public CenterSeekBarView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
paint = new Paint();
paint.setAntiAlias(true);
progressBackColor = Color.parseColor("#C2C2C2");
progressColor = Color.parseColor("#4388FF");
mThumbDrawColor = Color.parseColor("#4388FF");
mBackRectF = new RectF();
mProgressRectF = new RectF();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
width = getMeasuredWidth() - SizeUtils.dp2px(30);
}
public CenterSeekBarView setOnSeekBarChangeListener(OnSeekBarChangeListener l) {
mOnSeekBarChangeListener = l;
return this;
}
public void delProgress() {
setProgress(progress - (int) (minUnit * coefficient));
}
public void addProgress() {
setProgress(progress + (int) (minUnit * coefficient));
}
public void reset() {
setProgress(minProgress);
}
public void setProgress(int progress) {
if (!canMove){
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onError();
}
return;
}
if (progress <= maxProgress && progress >= minProgress - maxProgress) {
this.progress = progress;
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onProgress((float) progress / coefficient);
}
invalidate();
}
}
public void setCanMove(boolean canMove) {
this.canMove = canMove;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Log.i("slack","onDraw... " + mThumbRadius);
int centerX = getWidth() / 2; // x 是center
int centerY = getHeight() / 2; // y 是 2/3 高度
float startX = centerX - width / 2;
// draw background line
paint.setColor(progressBackColor);
/**
* 进度条的 高度
*/
float progressHeight = 9;
paint.setStrokeWidth(progressHeight);
paint.setStyle(Paint.Style.FILL); // 实心
mBackRectF.left = startX;
mBackRectF.top = centerY - progressHeight;
mBackRectF.right = startX + width;
mBackRectF.bottom = centerY;
/**
* progress 字体 背景 radius
*/
canvas.drawRoundRect(mBackRectF, 10, 10, paint);
paint.setStyle(Paint.Style.FILL);
paint.setColor(progressColor);
paint.setStrokeWidth(progressHeight);
startX = centerX;
progressPosition = startX + (int) ((progress * (width / 2f) / (maxProgress - minProgress)));
mProgressRectF.top = centerY - progressHeight;
mProgressRectF.bottom = centerY;
if (progress > 0) {
mProgressRectF.left = startX;
mProgressRectF.right = progressPosition;
} else {
mProgressRectF.left = progressPosition;
mProgressRectF.right = startX;
}
canvas.drawRoundRect(mProgressRectF, 10, 10, paint);
// draw point
paint.setColor(mThumbDrawColor);
canvas.drawCircle(progressPosition, centerY - progressHeight / 2, mThumbRadius, paint);
}
private long mLastTime;
@Override
public boolean onTouchEvent(MotionEvent event) {
if (!isEnabled()) {
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (canMove){
checkTouchingTarget(event);
}else {
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onError();
}
}
break;
case MotionEvent.ACTION_MOVE:
if (isTouchLegal) {
int tempProgress = (int) clamp((int) event.getRawX() - getLeft());
if (tempProgress == progress) {
break;
}
progress = tempProgress;
long currentTime = System.currentTimeMillis();
if (currentTime - mLastTime < 10) {
// 刷新 FPS 不超过 20 fps
break;
}
mLastTime = currentTime;
invalidate(); // 在UI线程中使用 刷新View
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onProgress((float) progress / coefficient);
}
}
break;
case MotionEvent.ACTION_UP:
invalidate();
break;
}
return true;
}
/**
* if touch , seekBar Thumb Animation
*/
private void checkTouchingTarget(MotionEvent event) {
if (isTouchingTarget(event)) {
postInvalidate();
}
}
public void setMaxProgress(int maxProgress) {
this.maxProgress = maxProgress * coefficient;
}
/**
* 判断是否 touch 在 seekBar thumb 上
*
* @param event
* @return
*/
private boolean isTouchingTarget(MotionEvent event) {
float location = progressPosition + getLeft();
isTouchLegal = event.getRawX() > location - DEFAULT_TOUCH_TARGET_SIZE
&& event.getRawX() < location + DEFAULT_TOUCH_TARGET_SIZE;
return isTouchLegal;
}
/**
* return progress
* -maxProgress minProgress maxProgress
* \------------------------0---------------------------\
* min center touch-->\ max
* (min center touch max are positions in the screen)
* touch progress = (touch - center) / (max - center) * maxProgress;
*/
private float clamp(int value) {
int centerX = getWidth() / 2;
float min = centerX - width / 2;// the start point
float max = centerX + width / 2;// the end point
if (value > centerX) {
if (value >= max) {
return maxProgress;
} else {
return (int) ((maxProgress - minProgress) * (value - centerX) / (width / 2f));
}
} else if (value < centerX) {
if (value <= min) {
return -maxProgress;
} else {
return (int) ((maxProgress - minProgress) * (value - centerX) / (width / 2f));
}
} else {
return minProgress;
}
}
public interface OnSeekBarChangeListener {
void onProgress(float progress);
void onError();
}
}
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