Android开发 详解开源项目CircleImageView

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/lizhaowei213/article/details/51116681

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);
    }

}