Android自定义View简易折线图控件（二）

继续练习自定义View，这次带来的是简易折线图，支持坐标点点击监听，效果如下：

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画坐标轴、画刻度、画点、连线。。x、y轴的数据范围是写死的 1 <= x <= 7 ，1 <= y <= 70 。。写活的话涉及到坐标轴刻度的动态计算、坐标点的坐标修改，想想就头大，这里只练习自定义View。

1、在res/values文件夹下新建attrs.xml文件，编写自定义属性：

<?xml version="1.0" encoding="utf-8"?>

2、新建LineChartView继承View，重写构造方法：

 public LineChartView(Context context) {
  this(context, null);
 }

 public LineChartView(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
 }

 public LineChartView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
 }

3、在第三个构造方法中获取自定义属性的值：

 TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.LineChartView, defStyleAttr, 0);
 mTextColor = ta.getColor(R.styleable.LineChartView_textColor, 0xff381a59);
 mLineColor = ta.getColor(R.styleable.LineChartView_lineColor, 0xff8e29fa);
 mPointColor = ta.getColor(R.styleable.LineChartView_pointColor, 0xffff5100);
 mPointRadius = DensityUtils.dp2px(context, 3);
 ta.recycle();

4、创建画图所使用的对象，如Paint、Path：

 mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
 mTextPaint.setStyle(Paint.Style.FILL);
 mTextPaint.setColor(mTextColor);
 mTextPaint.setTextSize(40);

 mLinePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
 mLinePaint.setStyle(Paint.Style.STROKE);
 mLinePaint.setColor(mLineColor);
 mLinePaint.setStrokeWidth(DensityUtils.dp2px(context, 2));
 mLinePaint.setStrokeCap(Paint.Cap.ROUND);
 mXyPath = new Path();

 mPointPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
 mPointPaint.setStyle(Paint.Style.FILL);
 mPointPaint.setColor(mPointColor);
 mPointCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
 mPointCirclePaint.setStyle(Paint.Style.STROKE);
 mPointCirclePaint.setStrokeWidth(DensityUtils.dp2px(context, 2));
 mPointCirclePaint.setColor(mLineColor);

5、重写onMeasure()方法，计算自定义View的宽高：

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  setMeasuredDimension(measuredDimension(widthMeasureSpec), measuredDimension(heightMeasureSpec));
 }

 private int measuredDimension(int measureSpec) {
  int result;
  int mode = MeasureSpec.getMode(measureSpec);
  int size = MeasureSpec.getSize(measureSpec);
  if (mode == MeasureSpec.EXACTLY) {
   result = size;
  } else {
   result = 500;
   if (mode == MeasureSpec.AT_MOST) {
    result = Math.min(result, size);
   }
  }
  return result;
 }

6、暴露一个设置x、y数据集合的方法：

 /**
  * 设置数据
  *
  * @param xList x轴数据集合
  * @param yList y轴数据集合
  */
 public void setDataList(List xList, List yList) {
  if (xList == null || yList == null || xList.size() == 0 || yList.size() == 0) {
   throw new IllegalArgumentException("没有数据");
  }
  if (xList.size() != yList.size()) {
   throw new IllegalArgumentException("x、y轴数据长度不一致");
  }
  setPointData(xList, yList);
  setPointAnimator();
 }

 /**
  * 设置坐标点的数据、坐标
  *
  * @param xList x轴数据集合
  * @param yList y轴数据集合
  */
 private void setPointData(List xList, List yList) {
  mPointList = new ArrayList<>();
  for (int i = 0; i < xList.size(); i++) {
   ChartPoint point = new ChartPoint();
   //设置坐标点的xy数据
   point.setxData(xList.get(i));
   point.setyData(yList.get(i));
   //计算坐标点的横纵坐标
   point.setX(xyMargin + xList.get(i) * (getWidth() - 2 * xyMargin) / maxX);
   point.setY(getHeight() - xyMargin - (getHeight() - 2 * xyMargin) * yList.get(i) / maxY);
   mPointList.add(point);
  }
 }

 /**
  * 设置坐标点移动的动画
  */
 private void setPointAnimator() {
  for (int i = 0; i < mPointList.size(); i++) {
   final ChartPoint point = mPointList.get(i);
   ValueAnimator anim;
   if (mLastPointList != null && mLastPointList.size() > 0) {
    anim = ValueAnimator.ofInt(mLastPointList.get(i).getY(), point.getY());
   } else {
    anim = ValueAnimator.ofInt(getHeight() - xyMargin, point.getY());
   }
   anim.setDuration(500);
   anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
     int value = (int) animation.getAnimatedValue();
     point.setY(value);
     invalidate();
    }
   });
   anim.start();
  }
  //储存坐标点集合
  mLastPointList = mPointList;
 }

7、重写onDraw()方法，绘制坐标轴、刻度，画点连线，注意坐标的计算：

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  if (mPointList == null || mPointList.size() == 0) {
   return;
  }

  mXyPath.reset();
  mXyPath.moveTo(xyMargin, 0);
  mXyPath.lineTo(xyMargin, getHeight() - xyMargin);
  mXyPath.lineTo(getWidth(), getHeight() - xyMargin);
  canvas.drawPath(mXyPath, mLinePaint);//画x、y坐标轴

  for (int i = 0; i < mPointList.size(); i++) {
   //画x轴刻度线
   int x = xyMargin + (i + 1) * (getWidth() - 2 * xyMargin) / mPointList.size();
   canvas.drawLine(x, getHeight() - xyMargin - graduatedLineLength, x, getHeight() - xyMargin, mLinePaint);
   //画y轴刻度线
   int y = getHeight() - xyMargin - (i + 1) * (getHeight() - 2 * xyMargin) / mPointList.size();
   canvas.drawLine(xyMargin, y, xyMargin + graduatedLineLength, y, mLinePaint);
   //画坐标轴刻度文本
   canvas.drawText(String.valueOf(mPointList.get(i).getxData()), x, getHeight() - mTextPaint.getTextSize() / 4, mTextPaint);
   canvas.drawText(String.valueOf((i + 1) * 10), 0, y + mTextPaint.getTextSize() / 2, mTextPaint);
  }
  //画连接线
  for (int i = 0; i < mPointList.size(); i++) {
   if (i != mPointList.size() - 1) {
    ChartPoint lastP = mPointList.get(i);
    ChartPoint nextP = mPointList.get(i + 1);
    canvas.drawLine(lastP.getX(), lastP.getY(), nextP.getX(), nextP.getY(), mLinePaint);
   }
  }
  //画坐标点
  for (int i = 0; i < mPointList.size(); i++) {
   ChartPoint point = mPointList.get(i);
   canvas.drawCircle(point.getX(), point.getY(), mPointRadius, mPointPaint);
   canvas.drawCircle(point.getX(), point.getY(), mPointRadius, mPointCirclePaint);
  }
 }

8、设置坐标点点击事件：

 private OnPointClickListener mOnPointClickListener;

 /**
  * 坐标点点击监听
  */
 public interface OnPointClickListener {
  /**
   * @param index 当前坐标点在数据集中的下标
   * @param point 当前坐标点对象
   */
  void onPointClick(int index, ChartPoint point);
 }

 public void setOnPointClickListener(OnPointClickListener onPointClickListener) {
  mOnPointClickListener = onPointClickListener;
 }

9、重写onTouchEvent()方法，判断当前点击的点是不是在坐标点范围内：

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
    //判断当前点击的点是否在坐标点范围内
    int curX = (int) event.getX();
    int curY = (int) event.getY();
    for (int i = 0; i < mPointList.size(); i++) {
     ChartPoint point = mPointList.get(i);
     double d1 = Math.pow(curX - point.getX(), 2);
     double d2 = Math.pow(curY - point.getY(), 2);
     //√￣(curX - cx)² + (curY - cy)² < R
     if (Math.sqrt(d1 + d2) < mPointRadius + 10) {//为了方便点击，把坐标点范围增大了10像素
      if (mOnPointClickListener != null) {
       mOnPointClickListener.onPointClick(i, point);
      }
     }
    }
    break;
  }
  return super.onTouchEvent(event);
 }

10、在activity_main.xml布局文件中使用该View：

<?xml version="1.0" encoding="utf-8"?>

11、在MainActivity.java中传入数据集合，并设置坐标点点击监听：

 btn.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   List xList = new ArrayList<>();
   List yList = new ArrayList<>();
   for (int i = 0; i < 7; i++) {
    xList.add(i + 1);
    int y = (int) (Math.random() * 70 + 1);
    yList.add(y);
   }
   chartView.setDataList(xList, yList);
  }
 });


 chartView.setOnPointClickListener(new LineChartView.OnPointClickListener() {
  @Override
  public void onPointClick(int position, ChartPoint point) {
   tv.setText("position:" + position + "\nx:" + point.getxData() + "\ny:" + point.getyData());
  }
});

致此大致步骤完成了，发现和上一篇步骤差不多。。代码已上传github：
https://github.com/MonkeyMushroom/LineChartView/tree/master

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持创新互联。

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