【移動(dòng)應(yīng)用開(kāi)發(fā)技術(shù)】Android中如何自定義View

【移動(dòng)應(yīng)用開(kāi)發(fā)技術(shù)】Android中如何自定義View

前言/upload/information/20210522/379/528689.jpg思維導(dǎo)圖/upload/information/20210522/379/528690.jpg工作流程@Override

protected

void

onMeasure(int

widthMeasureSpec,

int

heightMeasureSpec)

{

super.onMeasure(widthMeasureSpec,

heightMeasureSpec);

//用于獲取設(shè)定的模式

int

widthMode

=

MeasureSpec.getMode(widthMeasureSpec);

int

heightMode

=

MeasureSpec.getMode(heightMeasureSpec);

//

用于獲取設(shè)定的長(zhǎng)度

int

widthSize

=

MeasureSpec.getSize(widthMeasureSpec);

int

heightSize

=

MeasureSpec.getSize(heightMeasureSpec);

//

類似這樣的判斷，后面不過(guò)多復(fù)述

//

用于判斷是不是wrap_content

//

如果不進(jìn)行處理，效果會(huì)是match_parent

if(widthMode

==

MeasureSpec.AT_MOST

&&

heightMode

==

MeasureSpec.AT_MOST){

setMeasuredDimension(20,

20);

}

}/upload/information/20210522/379/528691.jpg/upload/information/20210522/379/528692.jpgdrawprivate

Paint

paint

=

new

Paint(Paint.ANTI_ALIAS_FLAG);

@Override

protected

void

onDraw(Canvas

canvas)

{

super.onDraw(canvas);

int

width

=

getWidth();

int

height

=

getHeight();

//

在畫布上進(jìn)行類似這樣的操作

canvas.drawLine(0,

height/2,

width,height/2,

paint);

}入門自定義View<?xml

version="1.0"

encoding="utf-8"?>

<resources>

<declare-styleable

name="DefaultView">

<attr

name="color"

format="color"/>

</declare-styleable>

</resources>/**

*

author:

ClericYi

*

time:

2020-01-30

*/

public

class

DefaultView

extends

View

{

private

Paint

paint

=

new

Paint(Paint.ANTI_ALIAS_FLAG);

private

int

mColor

=

Color.RED;

public

DefaultView(Context

context,

@Nullable

AttributeSet

attrs)

{

super(context,

attrs);

initAttrs(context,

attrs);

initDraw();

}

private

void

initAttrs(Context

context,

@Nullable

AttributeSet

attrs)

{

TypedArray

array

=

context.obtainStyledAttributes(attrs,

R.styleable.DefaultView);

//

從styleable中獲取的名字是系統(tǒng)會(huì)生成的，一般是

類名_name

的形式

mColor

=

array.getColor(R.styleable.DefaultView_color,

Color.GREEN);

//

獲取完資源后即使回收

array.recycle();

}

private

void

initDraw()

{

paint.setColor(mColor);

paint.setStrokeWidth(3f);

}

@Override

protected

void

onDraw(Canvas

canvas)

{

super.onDraw(canvas);

int

width

=

getWidth();

int

height

=

getHeight();

canvas.drawLine(0,

height/2,

width,height/2,

paint);

}

@Override

protected

void

onMeasure(int

widthMeasureSpec,

int

heightMeasureSpec)

{

super.onMeasure(widthMeasureSpec,

heightMeasureSpec);

int

widthMode

=

MeasureSpec.getMode(widthMeasureSpec);

int

heightMode

=

MeasureSpec.getMode(heightMeasureSpec);

int

widthSize

=

MeasureSpec.getSize(widthMeasureSpec);

int

heightSize

=

MeasureSpec.getSize(heightMeasureSpec);

if(widthMode

==

MeasureSpec.AT_MOST){

setMeasuredDimension(20,

20);

}

}

}基礎(chǔ)的性能優(yōu)化/upload/information/20210522/379/528693.png/upload/information/20210522/379/528694.jpg那如何做到性能優(yōu)化呢?方案1：減少嵌套層數(shù)。/upload/information/20210522/379/528695.png方案2：去除默認(rèn)的背景/upload/