【移動應(yīng)用開發(fā)技術(shù)】Android開發(fā)如何使用自定義View將圓角矩形繪制在Canvas上的方法

【移動應(yīng)用開發(fā)技術(shù)】Android開發(fā)如何使用自定義View將圓角矩形繪制在Canvas上的方法

這篇文章主要介紹了Android開發(fā)如何使用自定義View將圓角矩形繪制在Canvas上的方法，具有一定借鑒價(jià)值，感興趣的朋友可以參考下，希望大家閱讀完這篇文章之后大有收獲，下面讓在下帶著大家一起了解一下。Android開發(fā)使用自定義View將圓角矩形繪制在Canvas上的方法，具體如下：前幾天，公司一個(gè)項(xiàng)目中，頭像圖片需要添加圓角，這樣UI效果會更好看，于是寫了一個(gè)小的demo進(jìn)行圓角的定義，該處主要是使用BitmapShader進(jìn)行了渲染（如果要將一張圖片裁剪成橢圓或圓形顯示在屏幕上，也可以使用BitmapShader來完成）.BitmapShader類完成渲染圖片的基本步驟如下：1、創(chuàng)建BitmapShader類的對象

/**

*

Call

this

to

create

a

new

shader

that

will

draw

with

a

bitmap.

*

*

@param

bitmap

The

bitmap

to

use

inside

the

shader

*

@param

tileX

The

tiling

mode

for

x

to

draw

the

bitmap

in.

*

@param

tileY

The

tiling

mode

for

y

to

draw

the

bitmap

in.

*/

public

BitmapShader(Bitmap

bitmap,

TileMode

tileX,

TileMode

tileY)

{

}其中，Shader.TitleMode類型有三種，CALMP、MIRROR、REPEATCALMP：使用邊界顏色來填充剩余空間MIRROR：使用鏡像方式REPEAT：使用重復(fù)方式2、通過Paint的setShader(bitmapShafer)來設(shè)置畫筆3、使用已經(jīng)setShader(bitmapShafer)的畫筆來繪制圖形下面展示繪制圓角圖片的demo1、自定義RounderCornerImageView.java類package

com.example.test;

import

android.content.Context;

import

android.graphics.Bitmap;

import

android.graphics.BitmapShader;

import

android.graphics.Canvas;

import

android.graphics.Matrix;

import

android.graphics.Paint;

import

android.graphics.RectF;

import

android.graphics.Shader;

import

android.util.AttributeSet;

import

android.view.View;

public

class

RounderCornerImageView

extends

View

{

private

Bitmap

mImage;//

source

bitmap

private

Paint

mBitmapPaint;//paint

private

RectF

mBrounds;//rect

private

float

mRadius=20.0f;//round

public

RounderCornerImageView(Context

context)

{

this(context,

null);

}

public

RounderCornerImageView(Context

context,

AttributeSet

attrs)

{

this(context,

attrs,

0);

}

public

RounderCornerImageView(Context

context,

AttributeSet

attrs,

int

defStyleAttr)

{

super(context,

attrs,

defStyleAttr);

init();

}

private

void

init()

{

mBitmapPaint=new

Paint(Paint.ANTI_ALIAS_FLAG);

mBrounds=new

RectF();

}

@Override

protected

void

onMeasure(int

widthMeasureSpec,

int

heightMeasureSpec)

{

//

TODO

Auto-generated

method

stub

int

height,width;

height=width=0;

//obtain

bitmap

size

int

imageHeight,imageWidth;

if

(null!=mImage)

{

imageHeight=imageWidth=0;

}else

{

imageHeight=mImage.getHeight();

imageWidth=mImage.getWidth();

}

//obtain

best

measure

data

and

set

on

View

width=getMeasurement(widthMeasureSpec,imageWidth);

height=getMeasurement(heightMeasureSpec,

imageHeight);

//set

View

last

size

setMeasuredDimension(width,

height);

}

/**

*

measure

width

and

height

by

specMode

**/

private

int

getMeasurement(int

measureSpec,

int

contentSize)

{

int

specSize=MeasureSpec.getSize(measureSpec);

switch

(MeasureSpec.getMode(measureSpec))

{

case

MeasureSpec.AT_MOST:

return

Math.min(specSize,

contentSize);

case

MeasureSpec.UNSPECIFIED:

return

contentSize;

case

MeasureSpec.EXACTLY:

return

specSize;

default:

return

0;

}//switch

}

@Override

protected

void

onSizeChanged(int

w,

int

h,

int

oldw,

int

oldh)

{

if

(w!=oldw

||

h!=oldh)

{

int

imageWidth,imageHeight;

if

(null==mImage)

{

imageWidth=imageHeight=0;

}else

{

imageWidth=mImage.getWidth();

imageHeight=mImage.getHeight();

}

//center

point

int

left=(w-imageWidth)/2;

int

top=(h-imageHeight)/2;

mBrounds.set(left,

top,

left+imageWidth,

top+imageHeight);

if

(null!=mBitmapPaint.getShader())

{

Matrix

m=new

Matrix();

m.setTranslate(left,

top);

mBitmapPaint.getShader().setLocalMatrix(m);

}

}

}

public

void

setImage(Bitmap

bitmap)

{

if

(mImage!=bitmap)

{

mImage=bitmap;

if

(null!=mImage)

{

BitmapShader

shader=new

BitmapShader(bitmap,

Shader.TileMode.CLAMP,

Shader.TileMode.CLAMP);

mBitmapPaint.setShader(shader);

}else

{

mBitmapPaint.setShader(null);

}

requestLayout();//invalidated

the

layout

of

this

view

by

onDraw()

}

}

@Override

protected

void

onDraw(Canvas

canvas)

{

super.onDraw(canvas);

if

(null!=mBitmapPaint)

{

//draw

Round

Rect

canvas.drawRoundRect(mBrounds,

mRadius,

mRadius,

mBitmapPaint);

}

}

}2、顯示圓角圖片的RoundActivity.java類package

com.example.test;

import

android.app.Activity;

import

android.graphics.Bitmap;

import

android.graphics.BitmapFactory;

import

android.os.Bundle;

public

class

RoundActivity

extends

Activity{

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

RounderCornerImageView

view=new

RounderCornerImageView(this);

Bitmap

souBitmap=BitmapFactory.decodeResource(getResources(),

R.drawable.sun);

view.setImage(souBitmap);

setContentView(view);

}

}另外，附注下自定義View的一些基本步驟和必須實(shí)