主要实现刻度尺的效果，能够快速滑动刻度，设置刻度间距，刻度值，滑动回调。简单易用

效果图

textureView控件的选择

总结来说:

1.view的绘制在主线程里面，频繁绘制会导致主线程阻塞

2.我们知道一个surfaceview是异步绘制的，不阻塞主线程，但是它不支持平移、缩放、旋转，且很难放在srollview等控件里面

TextureView.SurfaceTextureListener

abstract void

Invoked when a

abstract boolean

Invoked when the specified

is about to be destroyed.

//textureview销毁时，可以在这个地方释放一些资源，比如camera

abstract void

Invoked when the

abstract void

@Override

public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {

mBorderRectF.set(mBorderPaint.getStrokeWidth(), mBorderPaint.getStrokeWidth(),

width - mBorderPaint.getStrokeWidth(), height - mBorderPaint.getStrokeWidth()); //设置一块矩形区域，

mWidth = mBorderRectF.width();

dis = (int)(mWidth / allBlockNum); //每个刻度间距,allBlockNum是小刻度的个数

refreshCanvas();

}

//刷新视图

private void refreshCanvas() {

if (mBorderRectF.isEmpty()) {

return;

}

Canvas canvas = lockCanvas();

if(canvas != null) {

canvas.drawColor(Color.WHITE);

drawBorder(canvas);

drawScaleMark(canvas);

drawMarkPoint(canvas);

}

unlockCanvasAndPost(canvas);

}

画出刻度线:由中间向两边画

//画出所有刻度:从中间向两边画

private void drawScaleMark(Canvas canvas) {

int count = 0;

final int centerX = (int)mBorderRectF.centerX();

if(mCenterNum > maxNum)

mCenterNum = maxNum;

if (mCenterNum < minNum)

mCenterNum = minNum;

if(numberListener != null)

numberListener.onChanged(mCenterNum);

while(true){

int left = centerX - dis * count;

int leftNum = mCenterNum - count * scaleNum;

int right = centerX + dis * count;

int rightNum = mCenterNum + count * scaleNum;

String leftText = String.valueOf(leftNum);

String rightText = String.valueOf(rightNum);

//间隔5刻度画文字信息

if(leftNum % (5*scaleNum) == 0) {

canvas.drawLine(left, canvas.getHeight() / 2, left, canvas.getHeight() - 1, mScaleMarkPaint);

mScaleMarkPaint.getTextBounds(leftText, 0, leftText.length(), mTextRect);

canvas.drawText(leftText, left - mTextRect.centerX(), canvas.getHeight() / 2, mScaleMarkPaint);

}

else

canvas.drawLine(left, canvas.getHeight() * 2 / 3, left, canvas.getHeight() - 1, mScaleMarkPaint);

if(rightNum % (5*scaleNum) == 0) {

canvas.drawLine(right, canvas.getHeight() / 2, right, canvas.getHeight() - 1, mScaleMarkPaint);

mScaleMarkPaint.getTextBounds(rightText, 0, rightText.length(), mTextRect);

canvas.drawText(rightText, right - mTextRect.centerX(), canvas.getHeight() / 2, mScaleMarkPaint);

}

else

canvas.drawLine(right, canvas.getHeight() * 2 / 3, right, canvas.getHeight() - 1, mScaleMarkPaint);

count++;

if(left < 0)

break;

}

}

手势判断

我把手势判断的逻辑代码写在ScaleScroller类中，onTouchEvent用来判断按下，移动和抬起三个手势。GestureDetector.SimpleOnGestureListener中的onFling来处理快速滑动

OnFling在手指快速滑动控件时触发，onfling有四个参数

(注意:onFling只能触发一次,但是快速滑动的效果是要在一定时间内做滚动处理，所以需要通过Scroller类+Handler的方式来帮助实现)

@Override

public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {

final int minX = -0x7fffffff;

final int maxX = 0x7fffffff;

lastX = 0;

scroller.fling(0, 0, (int)-velocityX, 0, minX, maxX, 0, 0); //滚动的距离有速度决定

handler.sendEmptyMessage(ON_FLING);

return true;

}

e1

The first down motion event that started the fling.       //按下时候的event

e2

The move motion event that triggered the current onFling.  //触发快速滑动时的event

velocityX

The velocity of this fling measured in pixels per second along the x axis.

velocityY

The velocity of this fling measured in pixels per second along the y axis.

private Handler handler = new Handler(){

@Override

public void handleMessage(Message msg) {

boolean isFinished = scroller.computeScrollOffset(); //判断滚动是否结束

int curX = scroller.getCurrX();

int delta = lastX - curX;

if(listener != null){

listener.onScroll(delta);

}

lastX = curX;

if(isFinished)

handler.sendEmptyMessage(ON_FLING);

else

listener.onFinished();

}

};