前言
随着google宣布kotlin作为官方开发语言，在Android中使用kotlin的趋势也越来越明显，最近被kotlin的文章轰炸了，所以决定上手试一下，试过之后，感觉靠它灵简直有魔性。特别是一句话写出一个复杂的循环的时候，简直被惊呆。而且使用AS，Java代码可以直接转成Kotlin。
效果图如下：
首先是这次自定义View的效果图，是一张饼图。如果是用java写的话也就几十行，觉得换成Kotlin的话可能会更少。
示例代码
主要的功能是可以任设定数据的个数，我这里是4个数据，可以任意设定每个数据的颜色。
#####首先上Kotlin代码#####
package top.greendami.mykotlinapp
import android.content.Context
import android.graphics.*
import android.util.AttributeSet
import android.view.View
/**
* Created by GreendaMi on 2017/4/10.
*/
class PPCircle : View {
var mDatas = ArrayList<Float>()
var mColors = ArrayList<Int>(4)
var mPaint: Paint = Paint()
constructor(mContext: Context) : super(mContext) {
val context = mContext
}
constructor(mContext: Context, mAttributeSet: AttributeSet) : super(mContext, mAttributeSet) {
initPaint()
val context = mContext
}
fun initPaint() {
mPaint.isAntiAlias = true
mPaint.style = Paint.Style.FILL_AND_STROKE
mPaint.color = 0xff44b391.toInt()
}
//长宽一致
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
val widthSpecSize = View.MeasureSpec.getSize(widthMeasureSpec)
val heightSpecSize = View.MeasureSpec.getSize(heightMeasureSpec)
val mLayoutSize = Math.min(widthSpecSize, heightSpecSize)
setMeasuredDimension(mLayoutSize, mLayoutSize)
}
/**
* 设置数据
*/
fun setData(data: ArrayList<Float>, colors: ArrayList<Int>) {
mDatas = data
mColors = colors
invalidate()
}
override fun onDraw(canvas: Canvas?) {
super.onDraw(canvas)
if (mDatas.size == 0) {
return
}
//切掉圆心
var mPath = Path()
mPath.addCircle(width / 2f, height / 2f, width / 2f * 0.4f,Path.Direction.CW)
mPath.close()
canvas?.clipPath(mPath, Region.Op.XOR)
var total = 0f
//此处亮点
mDatas.forEach { total += it }
var rf = RectF(0f, 0f, width.toFloat(), height.toFloat())
var startAngle = -90f//起点
var i = 0
mDatas.forEach {
mPaint.color = mColors[i]
var sweepAngle = it * 360 / total
canvas?.drawArc(rf, startAngle, sweepAngle, true, mPaint)
startAngle += sweepAngle
i++
}
}
}
设置数据
package top.greendami.mykotlinapp
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main2.*
class Main2Activity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main2)
var mDatas = ArrayList<Float>()
mDatas.add(1f)
mDatas.add(2f)
mDatas.add(4f)
mDatas.add(2f)
var mColors = ArrayList<Int>()
mColors.add(0xff83ccd2.toInt())
mColors.add(0xffc0e1ce.toInt())
mColors.add(0xfffac55e.toInt())
mColors.add(0xffef805f.toInt())
ppCircle.setData(mDatas,mColors)
}
}
<?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout 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" tools:context="top.greendami.mykotlinapp.Main2Activity"> <top.greendami.mykotlinapp.PPCircle android:id="@+id/ppCircle" android:layout_width="300dp" android:layout_height="300dp" app:layout_constraintBottom_toBottomOf="parent" android:layout_marginBottom="8dp" android:layout_marginRight="8dp" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" android:layout_marginTop="8dp" android:layout_marginLeft="8dp" app:layout_constraintLeft_toLeftOf="parent" /> </android.support.constraint.ConstraintLayout>
#####相同功能Java代码#####
package com.allrun.arsmartelevatorformanager.widget;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.graphics.Region;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;
import java.util.ArrayList;
import java.util.List;
/**
* Created by GreendaMi on 2017/4/11.
*/
public class PPCircle extends View {
Context mContext;
List<Float> mData = new ArrayList<Float>();//数据
List<Integer> mColors = new ArrayList<Integer>();//数据对应的颜色
Paint mPaint = new Paint();
public PPCircle(Context context) {
super(context);
}
public PPCircle(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
mContext = context;
initPaint();
}
private void initPaint() {
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int widthSpecSize = View.MeasureSpec.getSize(widthMeasureSpec);
int heightSpecSize = View.MeasureSpec.getSize(heightMeasureSpec);
int mLayoutSize = Math.min(widthSpecSize, heightSpecSize);
setMeasuredDimension(mLayoutSize, mLayoutSize);
}
public void setData(List<Float> mData, List<Integer> mColors) {
this.mData = mData;
this.mColors = mColors;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mData.size() == 0) {
return;
}
//切掉圆心
Path mPath =new Path();
mPath.addCircle(getWidth()/2,getWidth()/2,getWidth()/2* 0.4f ,Path.Direction.CW);
canvas.clipPath(mPath, Region.Op.XOR);
float total = 0;
for(float temp : mData){
total = total + temp;
}
RectF rf = new RectF(0f, 0f, getWidth(), getHeight());
float startAngle = -90f;//起点
int i = 0;
for(float temp : mData){
mPaint.setColor(mColors.get(i));
float sweepAngle = temp * 360 / total;
canvas.drawArc(rf, startAngle, sweepAngle, true, mPaint);
startAngle += sweepAngle;
i++;
}
}
}
说说Kotlin和Java感觉差异比较大的地方。首先是变量的生命，Kotlin声明时必须赋值或者初始化，java则不用，开始有点不习惯。Kotlin不需要分号结尾，Kotlin的循环用起来简直爽YY。
总结
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。
