Android自定义跑马灯文字效果

/**
 * Created by wuguangliang on 2018/12/21
 *
 * 跑马灯效果文字
 */
public class MarqueeHorizontalTextView extends AppCompatTextView {
  private float textLength = 0f;
  private float drawTextX = 0f;// 文本的横坐标
  public boolean isStarting = false;// 是否开始滚动
  private Paint paint = null;
  private String text = "";
  private long waitTime = 1000; //开始时等待的时间
  private int scrollTile = 2; //文字的滚动速度
  private int baseline;
 
  public MarqueeHorizontalTextView(Context context) {
    super(context);
    initView(context);
  }
 
  public MarqueeHorizontalTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView(context);
  }
 
  public MarqueeHorizontalTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    initView(context);
  }
 
  private void initView(Context context) {
    setMaxWidth(context.getResources().getDisplayMetrics().widthPixels / 2); //因为需求需要所以设置了最大宽度，如果不需要此功能可以删除掉
 
    paint = getPaint();
    paint.setColor(getTextColors().getColorForState(getDrawableState(), 0));
    text = getText().toString();
    if (TextUtils.isEmpty(text)) {
      return;
    }
    textLength = paint.measureText(text);
    isStarting = true;
  }
 
  @Override
  public void setTextColor(int color) {
    super.setTextColor(color);
    paint.setColor(color);
    start();
  }
 
  @Override
  public void setText(CharSequence text, BufferType type) {
    super.setText(text, type);
    this.text = text.toString();
    this.textLength = getPaint().measureText(text.toString());
    drawTextX = 0;
    start();
  }
 
  public void start() {
    isStarting = true;
    invalidate();
  }
 
  public void stop() {
    isStarting = false;
    invalidate();
  }
 
  @Override
  public void onDraw(Canvas canvas) {
    final Paint.FontMetricsInt fontMetrics = paint.getFontMetricsInt();
    baseline = (canvas.getHeight() - fontMetrics.bottom - fontMetrics.top) / 2;
    if (textLength <= canvas.getWidth()) {
      canvas.drawText(text, 0, baseline, paint);
      return;
    }
    canvas.drawText(text, -drawTextX, baseline, paint);
 
    if (!isStarting) {
      return;
    }
    if (drawTextX == 0) {
      postDelayed(() -> {
        drawTextX = 1;
        isStarting = true;
        invalidate();
      }, waitTime);
      isStarting = false;
      return;
    }
    drawTextX += scrollTile;
    //判断是否滚动结束
    if (drawTextX > textLength) {
      drawTextX = -canvas.getWidth();
 
    }
    invalidate();
  }
}