文字的测量高度

图片.png

宽度 测量调用 measureText
文字居中显示

高度的计算 ：

top + bottom -> bottom - top 最大高度
ascent+descent --》 decent - accent 正常高度
(ascent+descent ) 因为ascent为负数 所以 ---》descent-ascent

  Height/2  + (decent - accent)/2 - decent
  = Height/2 + decent/2  -accent/2 -decent
 = Height/2 - (decent + accent)/2

所以高度居中的基准

    Paint.FontMetrics fontMetrics = paint.getFontMetrics();
    float baseline = getHeight()/2 - (fontMetrics.descent + fontMetrics.ascent)/2;

文字居中

    float left = getWidth()/2 -width/2;
    float right = left + width*mPercent;
    Paint.FontMetrics fontMetrics = paint.getFontMetrics();
    float baseline = getHeight()/2 - (fontMetrics.descent + fontMetrics.ascent)/2;
    canvas.drawText(mText,left,baseline ,paint);

1.自定义属性

attrs.xml文件中

 <declare-styleable name="ColorTrackTextView">
    <attr name="originColor" format="color"/>
    <attr name="changeColor" format="color"/>
 </declare-styleable>

自定义类ColorTrackTextView

public class ColorTrackTextView extends TextView {
// 1. 实现一个文字两种颜色 - 绘制不变色字体的画笔
private Paint mOriginPaint;
//  实现一个文字两种颜色 - 绘制变色字体的画笔
private Paint mChangePaint;

public ColorTrackTextView(Context context) {
    this(context,null);
}
public ColorTrackTextView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}
public ColorTrackTextView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initPaint(context, attrs);
}
/**
 * 初始化画笔
 */
private void initPaint(Context context, AttributeSet attrs) {
    TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.ColorTrackTextView);

    int originColor = array.getColor(R.styleable.ColorTrackTextView_originColor, getTextColors().getDefaultColor());
    int changeColor = array.getColor(R.styleable.ColorTrackTextView_changeColor, getTextColors().getDefaultColor());

    mOriginPaint = getPaintByColor(originColor);
    mChangePaint = getPaintByColor(changeColor);

    // 回收
    array.recycle();
}
/**
 * 根据颜色获取画笔
 */
private Paint getPaintByColor(int color) {
    Paint paint = new Paint();
    // 设置颜色
    paint.setColor(color);
    // 设置抗锯齿
    paint.setAntiAlias(true);
    // 防抖动
    paint.setDither(true);
    // 设置字体的大小  就是TextView的字体大小
    paint.setTextSize(getTextSize());
    return paint;
}

2.绘制Text

  //clipRect 可以裁剪 左边用一个画笔去画  右边用另一个画笔去画 不断地改变中间值
  @Override
  protected void onDraw(Canvas canvas) {
 //        super.onDraw(canvas);
    //裁剪区域
    //根据进度把中间值计算出来
    // 根据进度把中间值算出来
    int middle = (int) (mCurrentProgress * getWidth());

    // 从左变到右
    if(mDirection == Direction.LEFT_TO_RIGHT) {  // 左边是红色右边是黑色
        // 绘制变色
        drawText(canvas, mChangePaint , 0, middle);
        drawText(canvas, mOriginPaint, middle, getWidth());
    }else{
        // 右边是红色左边是黑色
        drawText(canvas, mChangePaint, getWidth()-middle, getWidth());
        // 绘制变色
        drawText(canvas, mOriginPaint, 0, getWidth()-middle);
    }
}
/**
 * 绘制Text
 * @param canvas
 * @param paint
 * @param start
 * @param end
 */
private void drawText(Canvas canvas,Paint paint,int start,int end){
    canvas.save();
    // 绘制不变色
    Rect rect = new Rect(start, 0, end, getHeight());
    canvas.clipRect(rect);
    // 我们自己来画
    String text = getText().toString();
    Rect bounds = new Rect();
    paint.getTextBounds(text, 0, text.length(), bounds);
    // 获取字体的宽度
    int x = getWidth() / 2 - bounds.width() / 2;
    // 基线baseLine
    Paint.FontMetricsInt fontMetrics = paint.getFontMetricsInt();
    int dy = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
    int baseLine = getHeight() / 2 + dy;
    canvas.drawText(text, x, baseLine, paint);// 这么画其实还是只有一种颜色
    canvas.restore();
}

3.设置不同方向

   private Direction mDirection=Direction.LEFT_TO_RIGHT;
   public enum Direction{
    LEFT_TO_RIGHT,RIGHT_TO_LEFT
  }

4.提供对外开放的方法

public void setmDirection(Direction direction) {
    this.mDirection = direction;
}

public void setmCurrentProgress(float currentProgress) {
    this.mCurrentProgress = currentProgress;

    invalidate();
}

public void setChangeColor(int changeColor) {
    this.mChangePaint.setColor(changeColor);
}

public void setOriginColor(int originColor) {
    this.mOriginPaint.setColor(originColor);
}

5.具体使用

     tv = (ColorTrackTextView) findViewById(R.id.tv);

        ValueAnimator valueAnimator = ObjectAnimator.ofFloat(0, 1);
      valueAnimator.setDuration(2000);
       valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            float animatedValue = (float) animation.getAnimatedValue();
                tv.setmCurrentProgress(animatedValue);
        }
    });
    valueAnimator.start();

图片.png