[原创]android开源项目源码解析（一）----CircleImageView的源码解析

CircleImageView的代码很简洁，因此先将此工程作为源码解析系列的第一篇文章.

解析说明都在代码里了。

 /*
  * 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;//这里限制了只要一种模式：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();

     //用来变换 mBitmapShader，从而影响 mBitmapPaint的显示效果
     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;//滤镜效果，用在中间的bitmap上

     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);
     }

     //构造方法，获取属性文件中的定义，不必细说
     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();
     }

     //初始化方法，主要是设置ScaleType，ScaleType被限定为center_crop模式
     private void init() {
         super.setScaleType(SCALE_TYPE);
         mReady = true;

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

     @Override
     protected void onSizeChanged(int w, int h, int oldw, int oldh) {
         super.onSizeChanged(w, h, oldw, oldh);
         setup();//实现了refresh功能，当属性改变时，调用此方法，完成刷新界面的功能
     }

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

         //底色 mFillColor --> 画笔 mFillPaint
         if (mFillColor != Color.TRANSPARENT) {
             canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mFillPaint);
         }

         canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mDrawableRadius, mBitmapPaint);

         //边色 mBorderColor --> 画笔 mBorderPaint
         if (mBorderWidth != 0) {
             canvas.drawCircle(getWidth() / 2.0f, getHeight() / 2.0f, mBorderRadius, mBorderPaint);
         }
     }

     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);
         //这里判断长宽比例，即图片的实际长宽比例与view的长宽比例
         //如果图片更"扁"，则缩放的尺寸按照两者的高度来定
         //如果图片更"瘦"，则缩放的尺寸按照两者的宽度来定
         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);
         //可以简单的将BitmapShader类用来给Paint设置"填充颜色"，这种说法其实并不准确，shader"填充"效果针对的范围是整个canvas，
         //而paint显示的是这个paint实时画出来的部分。
         //shader可以设置matrix，用来缩放或位移
         mBitmapShader.setLocalMatrix(mShaderMatrix);
     }

     @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.");
         }
     }

     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) {
                 //COLORDRAWABLE_DIMENSION == 2，如果是ColorDrawable类型的，就取2x2大小
                 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;
         }
     }

 }