ShapeImageView 处理ImageView形状，原形圆角等

0. 源码地址

https://github.com/zhxhcoder/XImageView

1. 引用方法

compile 'com.zhxh:ximageviewlib:1.2'

2. 使用方法

举个栗子：

            <com.zhxh.ximageviewlib.ShapeImageView
                android:id="@+id/iv_avatar"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_centerVertical="true"
                android:layout_marginStart="15dp"
                android:layout_marginLeft="15dp"
                android:src="@drawable/ic_test_750_360"
                app:siv_border_color="@android:color/holo_purple"
                app:siv_border_size="1px"
                app:siv_round_radius="4dp"
                app:siv_shape="rect"
                tools:ignore="ContentDescription" />

3. 源码实现

3.1 属性定义与描述

    <declare-styleable name="ShapeImageView">
        <attr name="siv_shape" format="enum">
            <enum name="rect" value="1" />
            <enum name="circle" value="2" />
            <enum name="oval" value="3" />
        </attr>
        <attr name="siv_round_radius" format="dimension" />
        <attr name="siv_round_radius_leftTop" format="dimension" />
        <attr name="siv_round_radius_leftBottom" format="dimension" />
        <attr name="siv_round_radius_rightTop" format="dimension" />
        <attr name="siv_round_radius_rightBottom" format="dimension" />
        <attr name="siv_border_size" format="dimension" />
        <attr name="siv_border_color" format="color" />
    </declare-styleable>

3.2 代码实现

1，属性初始化
从AttributeSet 中初始化相关属性

    private void init(AttributeSet attrs) {
        TypedArray a = getContext().obtainStyledAttributes(attrs,
                R.styleable.ShapeImageView);
        mShape = a.getInt(R.styleable.ShapeImageView_siv_shape, mShape);
        mRoundRadius = a.getDimension(R.styleable.ShapeImageView_siv_round_radius, mRoundRadius);
        mBorderSize = a.getDimension(R.styleable.ShapeImageView_siv_border_size, mBorderSize);
        mBorderColor = a.getColor(R.styleable.ShapeImageView_siv_border_color, mBorderColor);

        mRoundRadiusLeftBottom = a.getDimension(R.styleable.ShapeImageView_siv_round_radius_leftBottom, mRoundRadius);
        mRoundRadiusLeftTop = a.getDimension(R.styleable.ShapeImageView_siv_round_radius_leftTop, mRoundRadius);
        mRoundRadiusRightBottom = a.getDimension(R.styleable.ShapeImageView_siv_round_radius_rightBottom, mRoundRadius);
        mRoundRadiusRightTop = a.getDimension(R.styleable.ShapeImageView_siv_round_radius_rightTop, mRoundRadius);

        a.recycle();
    }

2，关键数据初始化

    private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
    private static final int COLORDRAWABLE_DIMENSION = 2;
    public static int SHAPE_REC = 1; // 矩形
    public static int SHAPE_CIRCLE = 2; // 圆形
    public static int SHAPE_OVAL = 3; // 椭圆
    private final Matrix mShaderMatrix = new Matrix();
    private float mBorderSize = 0; // 边框大小,默认为0，即无边框
    private int mBorderColor = Color.WHITE; // 边框颜色，默认为白色
    private int mShape = SHAPE_REC; // 形状，默认为直接矩形
    private float mRoundRadius = 0; // 矩形的圆角半径,默认为0，即直角矩形

3，重新生成所需的Bitmap
我们覆盖ImageView的setImageResource与setImageDrawable函数，对生成的drawable对象重新自定义

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

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

自定义所需的Bitmap对象

    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 setupBitmapShader() {
        // super(context, attrs, defStyle)调用setImageDrawable时,成员变量还未被正确初始化
        if (mBitmapPaint == null) {
            return;
        }
        if (mBitmap == null) {
            invalidate();
            return;
        }
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        mBitmapPaint.setShader(mBitmapShader);

        // 固定为CENTER_CROP,使图片在ｖｉｅｗ中居中并裁剪
        mShaderMatrix.set(null);
        // 缩放到高或宽　与view的高或宽　匹配
        float scale = Math.max(getWidth() * 1f / mBitmap.getWidth(), getHeight() * 1f / mBitmap.getHeight());
        // 由于BitmapShader默认是从画布的左上角开始绘制，所以把其平移到画布中间，即居中
        float dx = (getWidth() - mBitmap.getWidth() * scale) / 2;
        float dy = (getHeight() - mBitmap.getHeight() * scale) / 2;
        mShaderMatrix.setScale(scale, scale);
        mShaderMatrix.postTranslate(dx, dy);
        mBitmapShader.setLocalMatrix(mShaderMatrix);
        invalidate();
    }

从上面代码我们看到，会调用 invalidate();重新绘制。
该方法的作用是什么呢？
我们进入 invalidate()方法：

public void invalidate() {
    invalidate(true);
}
void invalidate(boolean invalidateCache) {
    invalidateInternal(0, 0, mRight - mLeft, mBottom - mTop, invalidateCache, true);
}
void invalidateInternal(int l, int t, int r, int b, boolean invalidateCache,
        boolean fullInvalidate) {
    if (mGhostView != null) {
        mGhostView.invalidate(true);
        return;
    }

    //这里判断该子View是否可见或者是否处于动画中
    if (skipInvalidate()) {
        return;
    }

    //根据View的标记位来判断该子View是否需要重绘，假如View没有任何变化，那么就不需要重绘
    if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)) == (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)
            || (invalidateCache && (mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID)
            || (mPrivateFlags & PFLAG_INVALIDATED) != PFLAG_INVALIDATED
            || (fullInvalidate && isOpaque() != mLastIsOpaque)) {
        if (fullInvalidate) {
            mLastIsOpaque = isOpaque();
            mPrivateFlags &= ~PFLAG_DRAWN;
        }

        //设置PFLAG_DIRTY标记位
        mPrivateFlags |= PFLAG_DIRTY;

        if (invalidateCache) {
            mPrivateFlags |= PFLAG_INVALIDATED;
            mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
        }

        // Propagate the damage rectangle to the parent view.
        //把需要重绘的区域传递给父容器
        final AttachInfo ai = mAttachInfo;
        final ViewParent p = mParent;
        if (p != null && ai != null && l < r && t < b) {
            final Rect damage = ai.mTmpInvalRect;
            damage.set(l, t, r, b);
            //调用父容器的方法，向上传递事件
            p.invalidateChild(this, damage);
        }
        ...
    }
}

从上面代码代码我们看到，该方法的调用会引起View树的重绘，常用于内部调用(比如 setVisiblity())或者需要刷新界面的时候,需要在主线程(即UI线程)中调用该方法。可以看出，invalidate有多个重载方法，但最终都会调用invalidateInternal方法，在这个方法内部，进行了一系列的判断，判断View是否需要重绘，接着为该View设置标记位，然后把需要重绘的区域传递给父容器，即调用父容器的invalidateChild方法。
接着我们看ViewGroup#invalidateChild：

/**
 * Don't call or override this method. It is used for the implementation of
 * the view hierarchy.
 */
public final void invalidateChild(View child, final Rect dirty) {

    //设置 parent 等于自身
    ViewParent parent = this;

    final AttachInfo attachInfo = mAttachInfo;
    if (attachInfo != null) {
        // If the child is drawing an animation, we want to copy this flag onto
        // ourselves and the parent to make sure the invalidate request goes
        // through
        final boolean drawAnimation = (child.mPrivateFlags & PFLAG_DRAW_ANIMATION)
                == PFLAG_DRAW_ANIMATION;

        // Check whether the child that requests the invalidate is fully opaque
        // Views being animated or transformed are not considered opaque because we may
        // be invalidating their old position and need the parent to paint behind them.
        Matrix childMatrix = child.getMatrix();
        final boolean isOpaque = child.isOpaque() && !drawAnimation &&
                child.getAnimation() == null && childMatrix.isIdentity();
        // Mark the child as dirty, using the appropriate flag
        // Make sure we do not set both flags at the same time
        int opaqueFlag = isOpaque ? PFLAG_DIRTY_OPAQUE : PFLAG_DIRTY;

        if (child.mLayerType != LAYER_TYPE_NONE) {
            mPrivateFlags |= PFLAG_INVALIDATED;
            mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
        }

        //储存子View的mLeft和mTop值
        final int[] location = attachInfo.mInvalidateChildLocation;
        location[CHILD_LEFT_INDEX] = child.mLeft;
        location[CHILD_TOP_INDEX] = child.mTop;

        ...

        do {
            View view = null;
            if (parent instanceof View) {
                view = (View) parent;
            }

            if (drawAnimation) {
                if (view != null) {
                    view.mPrivateFlags |= PFLAG_DRAW_ANIMATION;
                } else if (parent instanceof ViewRootImpl) {
                    ((ViewRootImpl) parent).mIsAnimating = true;
                }
            }

            // If the parent is dirty opaque or not dirty, mark it dirty with the opaque
            // flag coming from the child that initiated the invalidate
            if (view != null) {
                if ((view.mViewFlags & FADING_EDGE_MASK) != 0 &&
                        view.getSolidColor() == 0) {
                    opaqueFlag = PFLAG_DIRTY;
                }
                if ((view.mPrivateFlags & PFLAG_DIRTY_MASK) != PFLAG_DIRTY) {
                    //对当前View的标记位进行设置
                    view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag;
                }
            }

            //调用ViewGrup的invalidateChildInParent，如果已经达到最顶层view,则调用ViewRootImpl
            //的invalidateChildInParent。
            parent = parent.invalidateChildInParent(location, dirty);

            if (view != null) {
                // Account for transform on current parent
                Matrix m = view.getMatrix();
                if (!m.isIdentity()) {
                    RectF boundingRect = attachInfo.mTmpTransformRect;
                    boundingRect.set(dirty);
                    m.mapRect(boundingRect);
                    dirty.set((int) (boundingRect.left - 0.5f),
                            (int) (boundingRect.top - 0.5f),
                            (int) (boundingRect.right + 0.5f),
                            (int) (boundingRect.bottom + 0.5f));
                }
            }
        } while (parent != null);
    }
}

可以看到，在该方法内部，先设置当前视图的标记位，接着有一个do…while…循环，该循环的作用主要是不断向上回溯父容器，求得父容器和子View需要重绘的区域的并集(dirty)。当父容器不是ViewRootImpl的时候，调用的是ViewGroup的invalidateChildInParent方法，我们来看看这个方法，ViewGroup#invalidateChildInParent:

public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
    if ((mPrivateFlags & PFLAG_DRAWN) == PFLAG_DRAWN ||
            (mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID) {
        if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE)) !=
                    FLAG_OPTIMIZE_INVALIDATE) {

            //将dirty中的坐标转化为父容器中的坐标，考虑mScrollX和mScrollY的影响
            dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
                    location[CHILD_TOP_INDEX] - mScrollY);

            if ((mGroupFlags & FLAG_CLIP_CHILDREN) == 0) {
                //求并集，结果是把子视图的dirty区域转化为父容器的dirty区域
                dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
            }

            final int left = mLeft;
            final int top = mTop;

            if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
                if (!dirty.intersect(0, 0, mRight - left, mBottom - top)) {
                    dirty.setEmpty();
                }
            }
            mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;

            //记录当前视图的mLeft和mTop值，在下一次循环中会把当前值再向父容器的坐标转化
            location[CHILD_LEFT_INDEX] = left;
            location[CHILD_TOP_INDEX] = top;

            if (mLayerType != LAYER_TYPE_NONE) {
                mPrivateFlags |= PFLAG_INVALIDATED;
            }
            //返回当前视图的父容器
            return mParent;

        }
        ...
    }
    return null;
}

可以看出，这个方法做的工作主要有：调用offset方法，把当前dirty区域的坐标转化为父容器中的坐标，接着调用union方法，把子dirty区域与父容器的区域求并集，换句话说，dirty区域变成父容器区域。最后返回当前视图的父容器，以便进行下一次循环。

回到上面所说的do…while…循环，由于不断向上调用父容器的方法，到最后会调用到ViewRootImpl的invalidateChildInParent方法，我们来看看它的源码，ViewRootImpl#invalidateChildInParent:

@Override
public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
    checkThread();
    if (DEBUG_DRAW) Log.v(TAG, "Invalidate child: " + dirty);

    if (dirty == null) {
        invalidate();
        return null;
    } else if (dirty.isEmpty() && !mIsAnimating) {
        return null;
    }

    if (mCurScrollY != 0 || mTranslator != null) {
        mTempRect.set(dirty);
        dirty = mTempRect;
        if (mCurScrollY != 0) {
            dirty.offset(0, -mCurScrollY);
        }
        if (mTranslator != null) {
            mTranslator.translateRectInAppWindowToScreen(dirty);
        }
        if (mAttachInfo.mScalingRequired) {
            dirty.inset(-1, -1);
        }
    }

    final Rect localDirty = mDirty;
    if (!localDirty.isEmpty() && !localDirty.contains(dirty)) {
        mAttachInfo.mSetIgnoreDirtyState = true;
        mAttachInfo.mIgnoreDirtyState = true;
    }

    // Add the new dirty rect to the current one
    localDirty.union(dirty.left, dirty.top, dirty.right, dirty.bottom);
    // Intersect with the bounds of the window to skip
    // updates that lie outside of the visible region
    final float appScale = mAttachInfo.mApplicationScale;
    final boolean intersected = localDirty.intersect(0, 0,
            (int) (mWidth * appScale + 0.5f), (int) (mHeight * appScale + 0.5f));
    if (!intersected) {
        localDirty.setEmpty();
    }
    if (!mWillDrawSoon && (intersected || mIsAnimating)) {
        scheduleTraversals();
    }
    return null;
}

可以看出，该方法所做的工作与上面的差不多，都进行了offset和union对坐标的调整，然后把dirty区域的信息保存在mDirty中，最后调用了scheduleTraversals方法，触发View的工作流程，由于没有添加measure和layout的标记位，因此measure、layout流程不会执行，而是直接从draw流程开始。

总结一下invalidate方法，当子View调用了invalidate方法后，会为该View添加一个标记位，同时不断向父容器请求刷新，父容器通过计算得出自身需要重绘的区域，直到传递到ViewRootImpl中，最终触发performTraversals方法，进行开始View树重绘流程(只绘制需要重绘的视图)。

回到ShapeImageView代码中，因为我们改变图片的形状不仅改变了大小，图片也相应变化，所以：

    /**
     * 对于普通的view,在执行到onDraw()时，背景图已绘制完成
     * <p>
     * 对于ViewGroup,当它没有背景时直接调用的是dispatchDraw()方法, 而绕过了draw()方法，
     * 当它有背景的时候就调用draw()方法，而draw()方法里包含了dispatchDraw()方法的调用，
     */
    @Override
    public void onDraw(Canvas canvas) {

        if (mBitmap != null) {
            if (mShape == SHAPE_CIRCLE) {
                canvas.drawCircle(mViewRect.right / 2, mViewRect.bottom / 2,
                        Math.min(mViewRect.right, mViewRect.bottom) / 2, mBitmapPaint);
            } else if (mShape == SHAPE_OVAL) {
                canvas.drawOval(mViewRect, mBitmapPaint);
            } else {
//                canvas.drawRoundRect(mViewRect, mRoundRadius, mRoundRadius, mBitmapPaint);
                mPath.reset();
                mPath.addRoundRect(mViewRect, new float[]{
                        mRoundRadiusLeftTop, mRoundRadiusLeftTop,
                        mRoundRadiusRightTop, mRoundRadiusRightTop,
                        mRoundRadiusRightBottom, mRoundRadiusRightBottom,
                        mRoundRadiusLeftBottom, mRoundRadiusLeftBottom,
                }, Path.Direction.CW);
                canvas.drawPath(mPath, mBitmapPaint);

            }
        }

        if (mBorderSize > 0) { // 绘制边框
            if (mShape == SHAPE_CIRCLE) {
                canvas.drawCircle(mViewRect.right / 2, mViewRect.bottom / 2,
                        Math.min(mViewRect.right, mViewRect.bottom) / 2 - mBorderSize / 2, mBorderPaint);
            } else if (mShape == SHAPE_OVAL) {
                canvas.drawOval(mBorderRect, mBorderPaint);
            } else {
//                canvas.drawRoundRect(mBorderRect, mRoundRadius, mRoundRadius, mBorderPaint);
                mPath.reset();
                mPath.addRoundRect(mBorderRect, new float[]{
                        mRoundRadiusLeftTop, mRoundRadiusLeftTop,
                        mRoundRadiusRightTop, mRoundRadiusRightTop,
                        mRoundRadiusRightBottom, mRoundRadiusRightBottom,
                        mRoundRadiusLeftBottom, mRoundRadiusLeftBottom,
                }, Path.Direction.CW);
                canvas.drawPath(mPath, mBorderPaint);
            }
        }
    }

另外需要注意的是，onSizeChanged回调，
因为View的大小不仅由View本身控制，而且受父控件的影响，所以我们在确定View大小的时候最好使用系统提供的onSizeChanged回调函数。它又四个参数，分别为 宽度，高度，上一次宽度，上一次高度。这个函数比较简单，我们只需关注 宽度(w), 高度(h) 即可，这两个参数就是View最终的大小。
它一般是视图大小发生变化的时候回调了，那么具体看源码是在layout的过程中出发的
在layout方法中会调用setFrame方法，在setFrame方法中又调用了sizeChange，在该方法里面回调了onSizeChanged，然后才去回调onLayout过程

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

initRect()方法用来设置图片的绘制区域

    //　设置图片的绘制区域
    private void initRect() {

        mViewRect.top = 0;
        mViewRect.left = 0;
        mViewRect.right = getWidth(); // 宽度
        mViewRect.bottom = getHeight(); // 高度

        // 边框的矩形区域不能等于ImageView的矩形区域，否则边框的宽度只显示了一半
        mBorderRect.top = mBorderSize / 2;
        mBorderRect.left = mBorderSize / 2;
        mBorderRect.right = getWidth() - mBorderSize / 2;
        mBorderRect.bottom = getHeight() - mBorderSize / 2;
    }