Android开发 详解开源项目CircleImageView

之前的项目中在需要显示圆形头像的地方，使用到了Github上的优秀开源项目CircleImageView

https://github.com/hdodenhof/CircleImageView

今天仔细地研究了这个项目，学习其原理，收获不少。

源码主要分为下面这几大部分

取图片Bitmap

取自定义属性

创建Paint画笔

计算内外圆半径

Canvas绘制内外圆形

一.取图片Bitmap

CircleImageView继承自ImageView

重写了下面几个方法

@Override
public void setImageBitmap(Bitmap bm) {
super.setImageBitmap(bm);
mBitmap = bm;
setup();
}

@Override
public void setImageDrawable(Drawable drawable) {
super.setImageDrawable(drawable);
mBitmap = getBitmapFromDrawable(drawable);
setup();
}

@Override
public void setImageResource(@DrawableRes int resId) {
super.setImageResource(resId);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}

@Override
public void setImageURI(Uri uri) {
super.setImageURI(uri);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}

重写这些方法的目的是为了让成员变量中的mBitmap取到在xml配置中的图片Bitmap引用。

而这些方法的调用先于构造函数。

此外，这些方法中都调用了setup函数。

这个setup函数很关键，详细的内容下面会讲到。

二.自定义属性

这里的入口可以从CircleImageView的使用得到

xml

<de.hdodenhof.circleimageview.CircleImageView

xmlns:app="http://schemas.android.com/apk/res-auto"

android:id="@+id/profile_image"

android:layout_width="96dp"

android:layout_height="96dp"

android:src="@drawable/profile"

app:civ_border_width="2dp"

app:civ_border_color="#FF000000"/>

从给出的使用样例可以看到这里有两个自定义的属性

civ_border_width 边框宽度

civ_border_color 边框颜色

从attrs文件中的定义可以看到，自定义的属性不止这些

<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="CircleImageView">
<attr name="civ_border_width" format="dimension" />
<attr name="civ_border_color" format="color" />
<attr name="civ_border_overlay" format="boolean" />
<attr name="civ_fill_color" format="color" />
</declare-styleable>
</resources>

civ_border_overlay 是一个boolean值，

代表边框是绘制在图片外部，不覆盖图片最外层，还是在图片之上绘制，覆盖最外层。

这么说可能会有点抽象

举个例个

假如在xml中这样使用

<csu.lzw.roundimageviewdemo.CircleImageView
android:layout_width="80dp"
android:layout_height="80dp"
app:civ_border_width="10dp"
app:civ_border_color="#000000"
app:civ_border_overlay="false"
android:src="@drawable/test"/>

看图

当civ_border_overlay为false时(默认为false)

当civ_border_overlay为true时

现在就应该明白两者的区别了吧

至于这些属性究竟是在绘制时如何使用的，接下来将会分析到

三.定制Paint画笔

1.首先，看一下默认的常量

private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;

private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
private static final int COLORDRAWABLE_DIMENSION = 2;

private static final int DEFAULT_BORDER_WIDTH = 0;
private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
private static final int DEFAULT_FILL_COLOR = Color.TRANSPARENT;
private static final boolean DEFAULT_BORDER_OVERLAY = false;

private final RectF mDrawableRect = new RectF();
private final RectF mBorderRect = new RectF();

private final Matrix mShaderMatrix = new Matrix();
private final Paint mBitmapPaint = new Paint();
private final Paint mBorderPaint = new Paint();
private final Paint mFillPaint = new Paint();

private int mBorderColor = DEFAULT_BORDER_COLOR;
private int mBorderWidth = DEFAULT_BORDER_WIDTH;
private int mFillColor = DEFAULT_FILL_COLOR;

默认是Center_Crop缩放模式，表示按比例将图片缩放至View大小，

默认边框颜色是黑色，边框宽度是0，即为没有边框。

默认civ_border_overlay=false.即默认将边框画在图片外部，不覆盖图片。

2.在构造函数中，取属性值

public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);
mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_civ_border_width, DEFAULT_BORDER_WIDTH);
mBorderColor = a.getColor(R.styleable.CircleImageView_civ_border_color, DEFAULT_BORDER_COLOR);
mBorderOverlay = a.getBoolean(R.styleable.CircleImageView_civ_border_overlay, DEFAULT_BORDER_OVERLAY);
mFillColor = a.getColor(R.styleable.CircleImageView_civ_fill_color, DEFAULT_FILL_COLOR);
a.recycle();
init();
}

重点是BorderColor 和BorderWidth这连个属性

接下来将会根据这两个属性创建连个画笔Paint

private void setup() {
if (!mReady) {
mSetupPending = true;
return;
}

if (getWidth() == 0 && getHeight() == 0) {
return;
}

if (mBitmap == null) {
invalidate();
return;
}

mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

mBitmapPaint.setAntiAlias(true);
mBitmapPaint.setShader(mBitmapShader);

mBorderPaint.setStyle(Paint.Style.STROKE);
mBorderPaint.setAntiAlias(true);
mBorderPaint.setColor(mBorderColor);
mBorderPaint.setStrokeWidth(mBorderWidth);

mFillPaint.setStyle(Paint.Style.FILL);
mFillPaint.setAntiAlias(true);
mFillPaint.setColor(mFillColor);

mBitmapHeight = mBitmap.getHeight();
mBitmapWidth = mBitmap.getWidth();

mBorderRect.set(0, 0, getWidth(), getHeight());
mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

mDrawableRect.set(mBorderRect);
if (!mBorderOverlay) {
mDrawableRect.inset(mBorderWidth, mBorderWidth);
}
mDrawableRadius = Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);

updateShaderMatrix();
invalidate();
}

创建画笔Paint的过程是在setup函数中。

那些标志位boolean的作用是这样的。

首先，通过设置mSetupPending和mReady控制第一次执行setup函数里的关键代码要在构造函数执行完毕时。

因为属性值的获取只能在构造函数中执行。

但前面所说，在setImageXXXX那些方法中，都调用了setup这个函数，原因是这样的。

当CircleImageView从Xml布局中，第一次加载的时候，因为setImageXXXX先于构造函数执行，但此时属性值并没有获取到，并不知道用户配置的边框宽度和颜色是多少，此时在setImageXXXX中，并不希望关键的创建画笔等步骤执行，但如果在CircleImageView第一次创建以后，用户在代码中因为完成了某项业务逻辑，需要更新头像，即重新设置CircleImageView的图片源时，此时会调用setImageXXXX函数，但这时候，希望setup里的关键的代码，创建画笔，绘制内外圆等操作执行，那么如何区分这两种情况呢？作者设置了这些boolean标志位来区分

if (!mReady) {
mSetupPending = true;
return;
}

mReady标志位默认为false，在构造函数的init方法里，才会将其设置为true,也就是说,如果setup在构造函数之前执行了，那么因为满足了if(!false)条件,将会直接return掉，不会执行setup关键代码。

而之后，在构造函数完成之后，如果手动的调用setImageXXXX,那么久不会满足!mReady条件，从而会执行setup关键代码

接下来是一个对Bitmap空指针的一个判断。

之后就进入了创建Paint画笔的关键部分

mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

创建一个渲染器，用mBitmap，也就是设置的图片来填充绘制区域 ，CLAMP表示如果图片太小的话，就直接拉伸。

创建图片内容BitmapPaint画笔

// 设置图片画笔反锯齿
mBitmapPaint.setAntiAlias(true);
// 设置图片画笔渲染器
mBitmapPaint.setShader(mBitmapShader);

创建边框BorderPaint画笔

mBorderPaint.setStyle(Paint.Style.STROKE);//STROKE应该很熟悉了把，自定义Drawable边框的时候也用到
mBorderPaint.setAntiAlias(true);//反锯齿
mBorderPaint.setColor(mBorderColor);//从属性中获取的画笔颜色
mBorderPaint.setStrokeWidth(mBorderWidth);//从属性中获取的画笔边界宽度

四.计算内外圆半径

mBitmapHeight = mBitmap.getHeight();
mBitmapWidth = mBitmap.getWidth();

mBorderRect.set(0, 0, getWidth(), getHeight());
mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

mDrawableRect.set(mBorderRect);
if (!mBorderOverlay) {
mDrawableRect.inset(mBorderWidth, mBorderWidth);
}
mDrawableRadius = Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);

updateShaderMatrix();
invalidate();

如果isBorderOverlay为false的话，就会把图片的范围嵌入进边框的范围中，这样边框就会绘制在图片的外面，而不是覆盖在图片上绘制。

getWidth和getHeight方法可以获取到View的宽和高，单位为像素px。

那么内外圆的半径就很好计算了。

内圆的半径即为Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);取宽和高最小的那一个的一半，剩下的较大者在updateShaderMatrix()函数中缩放

外圆的半径即为Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

因为外圆的画笔设置为了STROKE,那么边框为mBorderWidth的话，那么Stroke画笔的中心点应改是Stroke画出来粗粗的边框的中心位置，画笔的两个边界点即为，中心点向里向外，各+(-)borderwidth/2长度，那么外圆的半径，是从View中心,到Stroke画笔的中心，为BorderRect.height/2-borderwidth/2;

接下来有一个按比例缩放宽高的操作。

private void updateShaderMatrix() {
float scale;
float dx = 0;
float dy = 0;

mShaderMatrix.set(null);

if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {
scale = mDrawableRect.height() / (float) mBitmapHeight;
dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
} else {
scale = mDrawableRect.width() / (float) mBitmapWidth;
dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
}

mShaderMatrix.setScale(scale, scale);
mShaderMatrix.postTranslate((int) (dx + 0.5f) + mDrawableRect.left, (int) (dy + 0.5f) + mDrawableRect.top);

mBitmapShader.setLocalMatrix(mShaderMatrix);
}

因为在上面计算半径的时候，取了宽和高的最小值。但不能仅仅取完就完了，因为最后要绘制的图形是圆形，还需要对较大者等比缩放。

第一个if判断里的不等式，其实是对(mBitmapWidth / mDrawableRect.width()) > (mBitmapHeight / mDrawableRect.height())

的变形。

目的是为了取得最小的缩放比例

//y轴缩放 x轴平移 使得图片的y轴方向的边的尺寸缩放到图片显示区域（mDrawableRect）一样）

//x轴缩放 y轴平移 使得图片的x轴方向的边的尺寸缩放到图片显示区域（mDrawableRect）一样）

scale即位缩放的比例。

最后通过mShaderMatrix设置这个缩放的矩阵变换,postTranslate是指在setScale后平移.

五.Canvas绘制内外圆形

@Override
protected void onDraw(Canvas canvas) {
if (mBitmap == null) {
return;
}

if (mFillColor != Color.TRANSPARENT) {
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mFillPaint);
}
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mBitmapPaint);
if (mBorderWidth != 0) {
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mBorderRadius, mBorderPaint);
}
}

首先画内圆，圆心为getWidth/2,getHeight/2;半径为计算出来的内圆半径，画笔是mBitmapPaint.

然后判断用户是否自定义了边框宽度，若mBorderWidth!=0，说明自定义了，便画外圆,圆心同上，半径为计算处理的外圆半径，画笔为创建处来的那个stroke画笔。

基本解析OK了

附上源码

/*
* Copyright 2014 - 2015 Henning Dodenhof
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0 *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package de.hdodenhof.circleimageview;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.support.annotation.ColorInt;
import android.support.annotation.ColorRes;
import android.support.annotation.DrawableRes;
import android.util.AttributeSet;
import android.widget.ImageView;

public class CircleImageView extends ImageView {

private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;

private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
private static final int COLORDRAWABLE_DIMENSION = 2;

private static final int DEFAULT_BORDER_WIDTH = 0;
private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
private static final int DEFAULT_FILL_COLOR = Color.TRANSPARENT;
private static final boolean DEFAULT_BORDER_OVERLAY = false;

private final RectF mDrawableRect = new RectF();
private final RectF mBorderRect = new RectF();

private final Matrix mShaderMatrix = new Matrix();
private final Paint mBitmapPaint = new Paint();
private final Paint mBorderPaint = new Paint();
private final Paint mFillPaint = new Paint();

private int mBorderColor = DEFAULT_BORDER_COLOR;
private int mBorderWidth = DEFAULT_BORDER_WIDTH;
private int mFillColor = DEFAULT_FILL_COLOR;

private Bitmap mBitmap;
private BitmapShader mBitmapShader;
private int mBitmapWidth;
private int mBitmapHeight;

private float mDrawableRadius;
private float mBorderRadius;

private ColorFilter mColorFilter;

private boolean mReady;
private boolean mSetupPending;
private boolean mBorderOverlay;

public CircleImageView(Context context) {
super(context);

init();
}

public CircleImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);

TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);

mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_civ_border_width, DEFAULT_BORDER_WIDTH);
mBorderColor = a.getColor(R.styleable.CircleImageView_civ_border_color, DEFAULT_BORDER_COLOR);
mBorderOverlay = a.getBoolean(R.styleable.CircleImageView_civ_border_overlay, DEFAULT_BORDER_OVERLAY);
mFillColor = a.getColor(R.styleable.CircleImageView_civ_fill_color, DEFAULT_FILL_COLOR);

a.recycle();

init();
}

private void init() {
super.setScaleType(SCALE_TYPE);
mReady = true;

if (mSetupPending) {
setup();
mSetupPending = false;
}
}

@Override
public ScaleType getScaleType() {
return SCALE_TYPE;
}

@Override
public void setScaleType(ScaleType scaleType) {
if (scaleType != SCALE_TYPE) {
throw new IllegalArgumentException(String.format("ScaleType %s not supported.", scaleType));
}
}

@Override
public void setAdjustViewBounds(boolean adjustViewBounds) {
if (adjustViewBounds) {
throw new IllegalArgumentException("adjustViewBounds not supported.");
}
}

@Override
protected void onDraw(Canvas canvas) {
if (mBitmap == null) {
return;
}

if (mFillColor != Color.TRANSPARENT) {
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mFillPaint);
}
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mBitmapPaint);
if (mBorderWidth != 0) {
canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mBorderRadius, mBorderPaint);
}
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
setup();
}

public int getBorderColor() {
return mBorderColor;
}

public void setBorderColor(@ColorInt int borderColor) {
if (borderColor == mBorderColor) {
return;
}

mBorderColor = borderColor;
mBorderPaint.setColor(mBorderColor);
invalidate();
}

public void setBorderColorResource(@ColorRes int borderColorRes) {
setBorderColor(getContext().getResources().getColor(borderColorRes));
}

public int getFillColor() {
return mFillColor;
}

public void setFillColor(@ColorInt int fillColor) {
if (fillColor == mFillColor) {
return;
}

mFillColor = fillColor;
mFillPaint.setColor(fillColor);
invalidate();
}

public void setFillColorResource(@ColorRes int fillColorRes) {
setFillColor(getContext().getResources().getColor(fillColorRes));
}

public int getBorderWidth() {
return mBorderWidth;
}

public void setBorderWidth(int borderWidth) {
if (borderWidth == mBorderWidth) {
return;
}

mBorderWidth = borderWidth;
setup();
}

public boolean isBorderOverlay() {
return mBorderOverlay;
}

public void setBorderOverlay(boolean borderOverlay) {
if (borderOverlay == mBorderOverlay) {
return;
}

mBorderOverlay = borderOverlay;
setup();
}

@Override
public void setImageBitmap(Bitmap bm) {
super.setImageBitmap(bm);
mBitmap = bm;
setup();
}

@Override
public void setImageDrawable(Drawable drawable) {
super.setImageDrawable(drawable);
mBitmap = getBitmapFromDrawable(drawable);
setup();
}

@Override
public void setImageResource(@DrawableRes int resId) {
super.setImageResource(resId);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}

@Override
public void setImageURI(Uri uri) {
super.setImageURI(uri);
mBitmap = uri != null ? getBitmapFromDrawable(getDrawable()) : null;
setup();
}

@Override
public void setColorFilter(ColorFilter cf) {
if (cf == mColorFilter) {
return;
}

mColorFilter = cf;
mBitmapPaint.setColorFilter(mColorFilter);
invalidate();
}

private Bitmap getBitmapFromDrawable(Drawable drawable) {
if (drawable == null) {
return null;
}

if (drawable instanceof BitmapDrawable) {
return ((BitmapDrawable) drawable).getBitmap();
}

try {
Bitmap bitmap;

if (drawable instanceof ColorDrawable) {
bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION, COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
} else {
bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), BITMAP_CONFIG);
}

Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}

private void setup() {
if (!mReady) {
mSetupPending = true;
return;
}

if (getWidth() == 0 && getHeight() == 0) {
return;
}

if (mBitmap == null) {
invalidate();
return;
}

mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

mBitmapPaint.setAntiAlias(true);
mBitmapPaint.setShader(mBitmapShader);

mBorderPaint.setStyle(Paint.Style.STROKE);
mBorderPaint.setAntiAlias(true);
mBorderPaint.setColor(mBorderColor);
mBorderPaint.setStrokeWidth(mBorderWidth);

mFillPaint.setStyle(Paint.Style.FILL);
mFillPaint.setAntiAlias(true);
mFillPaint.setColor(mFillColor);

mBitmapHeight = mBitmap.getHeight();
mBitmapWidth = mBitmap.getWidth();

mBorderRect.set(0, 0, getWidth(), getHeight());
mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

mDrawableRect.set(mBorderRect);
if (!mBorderOverlay) {
mDrawableRect.inset(mBorderWidth, mBorderWidth);
}
mDrawableRadius = Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);

updateShaderMatrix();
invalidate();
}

private void updateShaderMatrix() {
float scale;
float dx = 0;
float dy = 0;

mShaderMatrix.set(null);

if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {
scale = mDrawableRect.height() / (float) mBitmapHeight;
dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
} else {
scale = mDrawableRect.width() / (float) mBitmapWidth;
dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
}

mShaderMatrix.setScale(scale, scale);
mShaderMatrix.postTranslate((int) (dx + 0.5f) + mDrawableRect.left, (int) (dy + 0.5f) + mDrawableRect.top);

mBitmapShader.setLocalMatrix(mShaderMatrix);
}

}