a note of DrawerArrowDrawable

CustomView.java

package com.example.ted.myapplication;

import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.Property;
import android.view.animation.Interpolator;
import android.view.animation.LinearInterpolator;

import static android.graphics.Paint.Style.STROKE;
/**
 * Created by ted on 2014/10/16.
 */
public class CustomView extends Drawable {
    Path first;
    Path second;
    Paint linePaint;
    Paint curve;
    Paint curve2;
    float param = 0;
    private ObjectAnimator mObjectAnimatorAngle;
    Rect bounds;
    Path three;
    Path four;
    public CustomView(){
        init();
    }

    private void init() {
        bounds = new Rect(0, 0, 1000,1000);
        first = new Path();
        first.moveTo(5.042f, 20f);
        first.rCubicTo(8.125f, -16.317f, 39.753f, -27.851f, 55.49f, -2.765f);

        second = new Path();
        second.moveTo(60.531f, 17.235f);
        second.rCubicTo(11.301f, 18.015f, -3.699f, 46.083f, -23.725f, 43.456f);
        linePaint = new Paint(Paint.SUBPIXEL_TEXT_FLAG | Paint.ANTI_ALIAS_FLAG);
        linePaint.setColor(Color.RED);
        linePaint.setStyle(STROKE);
        scalePath(first,0);
        scalePath(second,0);

        three = new Path();
        three.moveTo(64.959f, 20f);
        three.rCubicTo(4.457f, 16.75f, 1.512f, 37.982f, -22.557f, 42.699f);
        four = new Path();
        four.moveTo(42.402f, 62.699f);
        four.cubicTo(18.333f, 67.418f, 8.807f, 45.646f, 8.807f, 32.823f);
        scalePath(three,0);
        scalePath(four,0);

        curve = new Paint(Paint.SUBPIXEL_TEXT_FLAG | Paint.ANTI_ALIAS_FLAG);
        curve.setColor(Color.BLUE);

        curve2 = new Paint(Paint.SUBPIXEL_TEXT_FLAG | Paint.ANTI_ALIAS_FLAG);
        curve2.setColor(Color.YELLOW);

        setupAnimations();
    }

    private static void scalePath(Path path, float density) {

        Matrix scaleMatrix = new Matrix();
        scaleMatrix.setScale(2f,2f, 0f, 0f);
        path.transform(scaleMatrix);
    }

    private Property<CustomView, Float> mAngleProperty  =
            new Property<CustomView, Float>(Float.class, "angle") {
                @Override
                public Float get(CustomView object) {
                    return object.getCurrentParam();
                }

                @Override
                public void set(CustomView object, Float value) {
                    object.setCurrentParam(value);
                }
            };

    public Float getCurrentParam(){
        return param;
    }

    public void setCurrentParam(Float param){
        this.param = param;
        invalidateSelf();
    }
    private static final Interpolator ANGLE_INTERPOLATOR = new LinearInterpolator();
    private static final int ANGLE_ANIMATOR_DURATION = 2000;
    private void setupAnimations() {
        mObjectAnimatorAngle = ObjectAnimator.ofFloat(this, mAngleProperty, 1f);
        mObjectAnimatorAngle.setInterpolator(ANGLE_INTERPOLATOR);
        mObjectAnimatorAngle.setDuration(ANGLE_ANIMATOR_DURATION);
        mObjectAnimatorAngle.setRepeatMode(ValueAnimator.RESTART);
        mObjectAnimatorAngle.setRepeatCount(ValueAnimator.INFINITE);
        mObjectAnimatorAngle.start();

    }

    @Override public int getIntrinsicHeight() {
        return bounds.height();
    }

    @Override public int getIntrinsicWidth() {
        return bounds.width();
    }

    @Override
    public void draw(Canvas canvas) {
        float coordsA[] = { 0f, 0f };
        float coordsB[] = { 0f, 0f };
        PathMeasure measureFirst = new PathMeasure(first, false);
        PathMeasure measureFirst2 = new PathMeasure(second, false);
        PathMeasure measureFirst3 = new PathMeasure(three, false);
        PathMeasure measureFirst4 = new PathMeasure(four, false);
        float lengthFirst = measureFirst.getLength();
        float lengthFirst2 = measureFirst2.getLength();
        float lengthFirst3 = measureFirst3.getLength();
        float lengthFirst4 = measureFirst4.getLength();
        if(param <=0.5f) {
            param *= 2;
            measureFirst.getPosTan(lengthFirst * param, coordsA, null);
            measureFirst3.getPosTan(lengthFirst3 * param, coordsB, null);

        }else {
            param -= .5f;
            param *= 2;
//            measureFirst3.getPosTan(lengthFirst3 * param, coordsA, null);
            measureFirst4.getPosTan(lengthFirst4 * param, coordsA, null);
            measureFirst2.getPosTan(lengthFirst2 * param, coordsB, null);
        }


        canvas.drawPath(first,curve);
        canvas.drawPath(second,curve2);
        canvas.drawPath(three,curve);
        canvas.drawPath(four,curve2);
        canvas.drawLine(coordsA[0], coordsA[1], coordsB[0], coordsB[1], linePaint);

        if(param==1){
            param = 0;
        }

    }

    @Override
    public void setAlpha(int alpha) {

    }

    @Override
    public void setColorFilter(ColorFilter cf) {

    }

    @Override
    public int getOpacity() {
        return 0;
    }
}