velocimeter-view android的测速仪效果的进度条 ，自定义VelocimeterView 的一个圆形进度条，
设置 app:inside_progress_color， app:external_progress_color，app:progress_blur_color
， app:bottom_velocimeter_color， app:internal_velocimeter_color等几层view叠加实现的。

运行效果：

源码：

package com.github.glomadrian.velocimeter;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.SeekBar;
import com.github.glomadrian.velocimeterlibrary.VelocimeterView;

public class MainActivity extends AppCompatActivity {

private SeekBar seek;
  private VelocimeterView velocimeter;
  private VelocimeterView velocimeter2;

@Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    seek = (SeekBar) findViewById(R.id.seek);
    seek.setOnSeekBarChangeListener(new SeekListener());
    velocimeter = (VelocimeterView) findViewById(R.id.velocimeter);
    velocimeter2 = (VelocimeterView) findViewById(R.id.velocimeter2);
  }

private class SeekListener implements SeekBar.OnSeekBarChangeListener {

@Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
      velocimeter.setValue(progress, true);
      velocimeter2.setValue(progress, true);
    }

@Override public void onStartTrackingTouch(SeekBar seekBar) {
      //Empty
    }

@Override public void onStopTrackingTouch(SeekBar seekBar) {
      //Empty
    }
  }
}

项目完整源码：http://www.itlanbao.com/code/20150915/10000/100529.html