package home.smart.fly.animations.customview;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import home.smart.fly.animations.R;

/**
 * Created by Rookie on 2017/10/30.
 */

public class BitmapMeshView extends View {

    private Bitmap mBitmap;

    //定义两个常量,这两个常量指定该图片横向,纵向上都被划分为20格
    private final int WIDTH = 20;
    private final int HEIGHT = 20;
    //记录该图片上包含441个顶点
    private final int COUNT = (WIDTH + 1) * (HEIGHT + 1);
    //定义一个数组,记录Bitmap上的21*21个点的坐标
    private final float[] verts = new float[COUNT * 2];
    //定义一个数组,记录Bitmap上的21*21个点经过扭曲后的坐标
    //对图片扭曲的关键就是修改该数组里元素的值
    private final float[] orig = new float[COUNT * 2];

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


    public BitmapMeshView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public BitmapMeshView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.cat);
        //获取图片宽度和高度
        float bitmapWidth = mBitmap.getWidth();
        float bitmapHeight = mBitmap.getHeight();
        int index = 0;
        for (int y = 0; y <= HEIGHT; y++) {
            float fy = bitmapHeight * y / HEIGHT;
            for (int x = 0; x <= WIDTH; x++) {
                float fx = bitmapWidth * x / WIDTH;
                //初始化orig,verts数组
                //初始化,orig,verts两个数组均匀地保存了21 * 21个点的x,y坐标　
                orig[index * 2 + 0] = verts[index * 2 + 0] = fx;
                orig[index * 2 + 1] = verts[index * 2 + 1] = fy;
                index += 1;
            }
        }
        //设置背景色
        setBackgroundColor(Color.WHITE);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //对bitmap按verts数组进行扭曲
        //从第一个点(由第5个参数0控制)开始扭曲
        canvas.drawBitmapMesh(mBitmap, WIDTH, HEIGHT, verts, 0, null, 0, null);
    }

    /**
     * 工具方法,用于根据触摸事件的位置计算verts数组里各元素的值
     */
    private void warp(float cx, float cy) {
        for (int i = 0; i < COUNT * 2; i += 2) {
            float dx = cx - orig[i + 0];
            float dy = cy - orig[i + 1];
            float dd = dx * dx + dy * dy;
            //计算每个坐标点与当前点(cx,cy)之间的距离
            float d = (float) Math.sqrt(dd);
            //计算扭曲度，距离当前点(cx,cy)越远，扭曲度越小
            float pull = 80000 / ((float) (dd * d));
            //对verts数组(保存bitmap　上21 * 21个点经过扭曲后的坐标)重新赋值
            if (pull >= 1) {
                verts[i + 0] = cx;
                verts[i + 1] = cy;
            } else {
                //控制各顶点向触摸事件发生点偏移
                verts[i + 0] = orig[i + 0] + dx * pull;
                verts[i + 1] = orig[i + 1] + dx * pull;
            }
        }
        //通知View组件重绘
        invalidate();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //调用warp方法根据触摸屏事件的坐标点来扭曲verts数组
        warp(event.getX(), event.getY());
        return true;
    }
}
