kotlin第六课加载动画

loading中的代码：

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.os.Build
import android.util.AttributeSet
import android.view.View
import androidx.annotation.RequiresApi
import java.text.AttributedCharacterIterator
import java.util.jar.Attributes

class LoadingView(context:Context,attrs:AttributeSet? = null)
    : View(context,attrs)
{
    val bgPaint:Paint = Paint().also {
        it.color = Color.YELLOW
        it.strokeWidth = 20f
        it.style = Paint.Style.STROKE
    }//创建画笔
    val fgPaint:Paint = Paint().also {
        it.color = Color.RED
        it.strokeWidth = 20f
        it.style = Paint.Style.STROKE
        it.strokeCap = Paint.Cap.ROUND
    }
    //onDraw会被多次调用
    //动画因子
    @RequiresApi(Build.VERSION_CODES.LOLLIPOP)
    var sweepAngle = 0f
    set(value){
        field = value
        invalidate()
    }
    @RequiresApi(Build.VERSION_CODES.LOLLIPOP)
    override fun onDraw(canvas: Canvas) {//运行起来后系统自动调用
        //super.onDraw(canvas)//如何绘制一个圆：画板（canvas）、画笔（有粗细颜色）Paint
        val cx = width.toFloat()/2
        val cy = height.toFloat()/2
        val radius = Math.min(width.toFloat(),height.toFloat())/2-bgPaint.strokeWidth
        canvas?.drawCircle(cx, cy, radius.toFloat(),bgPaint)
        //进度
        canvas?.drawArc(fgPaint.strokeWidth,fgPaint.strokeWidth,width.toFloat()-fgPaint.strokeWidth,height.toFloat()-fgPaint.strokeWidth, -90f, sweepAngle,false,fgPaint)
    }
}

MainActivity中的代码：

import android.animation.ValueAnimator
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.MotionEvent
//on开头一般是一些事件，由系统调用
class MainActivity : AppCompatActivity() {//主界面
    lateinit var loadingView: LoadingView
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)//把我们的内容视图R.layout.activity_main解析、复制给主视图
        loadingView = findViewById(R.id.progressView)  //在xml文件中找到id为progressView的控件
    }

    override fun onTouchEvent(event: MotionEvent?): Boolean {//返回true会把事件消费掉，false会传给下一层
        if (event?.action == MotionEvent.ACTION_DOWN){//触发动画
            ValueAnimator.ofFloat(0f,360f).apply {

                //已经创建对象
                this.duration = 3000 // this可省略
                addUpdateListener {
                    //获取当前产生的值
                    val value = it.animatedValue as Float
                    //改变LoadingView变化因子的值
                    loadingView.sweepAngle = value
                    Log.v("ppp","$value")
                }

                start()
                repeatCount = 50000000
            }//动画管理器
        }
            //dowm\move\up三个动作
        return true
    }
}
/**
1、百分比显示在中间
        2、两个按钮：开始下载、暂停下载和继续
*/