41音乐频谱



/*使用方法：在Visualizer的获取到fft数据时调用本View的updateVisualizer(byte[] bytes)把fft传过来*/

package com.gh.lighting.widget.music;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Shader;
import android.view.View;

public class VisualizerView extends View {
 /* 控制有效数据中显示的竖条数和下落速度 */
 private static final int LENGTH = 1024;
 private static final int NUMBER = 32;
 private static final int DOWN_SPEED = 32;
 private static final float STROKE_WIDTH = 27f;
 private static final int ALPHA = 88;

 /* 要画实际和倒影的点 */
 private byte[] mBytes;
 private float[] nowPoints;// 当前位置
 private float[] lastPoints; // 上一次位置
 private float[] reflectionPoints;// 倒影
 /* 画笔 */
 private Paint realPaint = new Paint();
 private Paint reflectionPaint = new Paint();// 倒影
 private static final int MIDDLE_COLOR = Color.rgb(255, 0, 0);
 private static final int STROKE_COLOR = Color.rgb(0, 255, 0);

 public VisualizerView(Context context) {
  super(context);
  init();
 }

 /* 初始化画笔 */
 private void init() {
  LinearGradient mRadialGradient = new LinearGradient(0, 0, 0, 400,
    new int[] { STROKE_COLOR, MIDDLE_COLOR }, null,
    Shader.TileMode.MIRROR);
  mBytes = null;
  realPaint.setStrokeWidth(STROKE_WIDTH);
  realPaint.setAntiAlias(true);
  realPaint.setShader(mRadialGradient);
  reflectionPaint.setStrokeWidth(STROKE_WIDTH);
  reflectionPaint.setAntiAlias(true);
  reflectionPaint.setShader(mRadialGradient);
  reflectionPaint.setAlpha(ALPHA);
 }

 /* 外部更新接口 */
 public void updateVisualizer(byte[] bytes) {
  mBytes = bytes;
  invalidate();
 }

 /**
  * 画图
  */
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  if (mBytes == null || mBytes.length < 3) {
   return;
  }
  byte[] model1 = new byte[LENGTH / 2 + 1];
  model1[0] = (byte) Math.abs(mBytes[1]);
  for (int i = 2, j = 1; i < LENGTH / 4; i += 2, j++) {
   model1[j] = (byte) Math.hypot(mBytes[i], mBytes[i + 1]);
  }

  byte[] model = new byte[LENGTH / 2 + 1];
  model[0] = (byte) Math.abs(model1[1]);
  for (int i = 2, j = 1; i < LENGTH / 2; i += 2, j++) {
   model[j] = (byte) Math.max(model1[i], model1[i + 1]);
   if (j > 0) {
    model[j] = (byte) ((model[j] + model[j - 1]) / 2);
   }
  }

  if (nowPoints == null || nowPoints.length < NUMBER * 4) {
   nowPoints = new float[NUMBER * 4];
   reflectionPoints = new float[NUMBER * 4];
   lastPoints = new float[NUMBER * 4];
  }
  for (int i = 0; i < NUMBER; i++) {
   if (model[i] < 0) {
    model[i] = 127;
   }
   if (model[i] > 127) {
    model[i] = 127;
   }
   float zoom = (float) (14.5 * i / NUMBER + 2.5);
   if (model[i] < 5) {
    zoom = 4;
   }

   nowPoints[i * 4] = getWidth() * i / NUMBER;
   nowPoints[i * 4 + 1] = getHeight() / 5 * 3;
   nowPoints[i * 4 + 2] = getWidth() * i / NUMBER;
   nowPoints[i * 4 + 3] = 1 + getHeight() / 5 * 3 - model[i] * zoom;

   reflectionPoints[i * 4] = nowPoints[i * 4];
   reflectionPoints[i * 4 + 1] = nowPoints[i * 4 + 1] + 5;
   reflectionPoints[i * 4 + 2] = nowPoints[i * 4 + 2];
   reflectionPoints[i * 4 + 3] = nowPoints[i * 4 + 3] + model[i]
     * zoom * 5 / 3;

   lastPoints[i * 4] = nowPoints[i * 4];
   lastPoints[i * 4 + 1] = nowPoints[i * 4];
   lastPoints[i * 4 + 2] = nowPoints[i * 4];
   if (lastPoints[i * 4 + 3] > 0
     && nowPoints[i * 4 + 3] > lastPoints[i * 4 + 3]
       + DOWN_SPEED) {
    nowPoints[i * 4 + 3] = lastPoints[i * 4 + 3] + DOWN_SPEED;
    reflectionPoints[i * 4 + 3] = (getHeight() * 2 - nowPoints[i * 4 + 3])
      / 2 - DOWN_SPEED / 2;
   }
   lastPoints[i * 4 + 3] = nowPoints[i * 4 + 3];
  }
  canvas.drawLines(nowPoints, realPaint);
  canvas.drawLines(reflectionPoints, reflectionPaint);
 }
}