Kotlin01.手指小球

最新推荐文章于 2022-08-20 16:48:31 发布

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本文介绍了一个自定义的Android DrawView类，该类继承自View，用于实现屏幕上的绘图功能。通过覆写onDraw方法，使用Paint绘制红色圆形，并通过onTouchEvent响应触摸事件更新圆的位置。同时展示了如何在MainActivity中集成并显示DrawView。

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
    android:id="@+id/root"
tools:context=".MainActivity"
    android:orientation="horizontal">
<com.example.a01helloworld.DrawView
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

</LinearLayout>

MainActivity.kt

package com.example.a01helloworld

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.ViewGroup
import android.widget.Button
import android.widget.ImageView
import android.widget.LinearLayout
import android.widget.TextView

class MainActivity : AppCompatActivity() {
    private var images = intArrayOf(R.mipmap.bg1, R.mipmap.bg2, R.mipmap.bg3, R.mipmap.bg4)
    private var currentImg = 0
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val root = findViewById<LinearLayout>(R.id.root)
        val draw = DrawView(this)
        draw.minimumWidth = 500
        draw.minimumHeight = 300
        root.addView(draw)
    }

}

DrawView.kt

package com.example.a01helloworld

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View

class DrawView : View{

    private var currentX = 40f
    private var currentY = 50f
    private var  p = Paint()
    constructor(context : Context) : super(context)
    constructor(context: Context, set: AttributeSet) : super(context, set)
    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        p.color =  Color.RED
        canvas!!.drawCircle(currentX, currentY, 15F, p)
    }

    override fun onTouchEvent(event: MotionEvent?): Boolean {
        currentX = event!!.x
        currentY = event!!.y
        invalidate()
        return true
    }
}