VUMeter.java

package com.androsz.flatnote.soundrecorder;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;

import com.androsz.flatnote.R;

public class VUMeter extends View {
	static final float PIVOT_RADIUS = 3.5f;
	static final float PIVOT_Y_OFFSET = 10f;
	static final float SHADOW_OFFSET = 2.0f;
	static final float DROPOFF_STEP = 0.18f;
	static final float SURGE_STEP = 0.35f;
	static final long ANIMATION_INTERVAL = 70;

	Paint mPaint, mShadow;
	float mCurrentAngle;

	Recorder mRecorder;

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

	public VUMeter(Context context, AttributeSet attrs) {
		super(context, attrs);
		init(context);
	}

	void init(Context context) {
		final Drawable background = context.getResources().getDrawable(
				R.drawable.vumeter);
		setBackgroundDrawable(background);

		mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
		mPaint.setColor(Color.WHITE);
		mShadow = new Paint(Paint.ANTI_ALIAS_FLAG);
		mShadow.setColor(Color.argb(60, 0, 0, 0));

		mRecorder = null;

		mCurrentAngle = 0;
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);

		final float minAngle = (float) Math.PI / 8;
		final float maxAngle = (float) Math.PI * 7 / 8;

		float angle = minAngle;
		if (mRecorder != null) {
			angle += (maxAngle - minAngle) * mRecorder.getMaxAmplitude()
					/ 32768;
		}

		if (angle > mCurrentAngle) {
			mCurrentAngle = angle;
		} else {
			mCurrentAngle = Math.max(angle, mCurrentAngle - DROPOFF_STEP);
		}

		mCurrentAngle = Math.min(maxAngle, mCurrentAngle);

		final float w = getWidth();
		final float h = getHeight();
		final float pivotX = w / 2;
		final float pivotY = h - PIVOT_RADIUS - PIVOT_Y_OFFSET;
		final float l = h * 4 / 5;
		final float sin = (float) Math.sin(mCurrentAngle);
		final float cos = (float) Math.cos(mCurrentAngle);
		final float x0 = pivotX - l * cos;
		final float y0 = pivotY - l * sin;
		canvas.drawLine(x0 + SHADOW_OFFSET, y0 + SHADOW_OFFSET, pivotX
				+ SHADOW_OFFSET, pivotY + SHADOW_OFFSET, mShadow);
		canvas.drawCircle(pivotX + SHADOW_OFFSET, pivotY + SHADOW_OFFSET,
				PIVOT_RADIUS, mShadow);
		canvas.drawLine(x0, y0, pivotX, pivotY, mPaint);
		canvas.drawCircle(pivotX, pivotY, PIVOT_RADIUS, mPaint);

		if (mRecorder != null && mRecorder.state() == Recorder.RECORDING_STATE) {
			postInvalidateDelayed(ANIMATION_INTERVAL);
		}
	}

	public void setRecorder(Recorder recorder) {
		mRecorder = recorder;
		invalidate();
	}
}