Android--自定义View入门

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自定义一个类,继承自Viewpackage view;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.view.View;/** * Created by Administrator on 2017/11/28. */public class MyView extends View {    private Paint mPaint = new Paint();    public MyView(Context context) {        super(context);        init();    }    public MyView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        init();    }    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init(){        mPaint.setColor(Color.BLUE);//设置线宽mPaint.setStrokeWidth(10);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);//实现圆 等        canvas.drawCircle(getWidth()/2,getHeight()/2,100,mPaint);        canvas.drawRect(200,200,600,500,mPaint);        canvas.drawLine(100,100,1000,1500,mPaint);    }}//自定义控件<?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="com.example.administrator.practise.MainActivity">    <view.MyView        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></android.support.constraint.ConstraintLayout>
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