自定义圆角ImageView控件

这个就当工具类用吧，因为直接是继承的ImageView.所以也具备了ImageView所有的特点，不同的是，可以自动裁剪成圆角图片。看效果吧。

效果还是不错的。使用方式：

直接在配置中添加依赖

compile 'de.hdodenhof:circleimageview:2.1.0'

并且查看其源码，思路也非常简单清晰：

/*
 * Copyright 2014 - 2016 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;
    private boolean mDisableCircularTransformation;

    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 (mDisableCircularTransformation) {
            super.onDraw(canvas);
            return;
        }

        if (mBitmap == null) {
            return;
        }

        if (mFillColor != Color.TRANSPARENT) {
            canvas.drawCircle(mDrawableRect.centerX(), mDrawableRect.centerY(), mDrawableRadius, mFillPaint);
        }
        canvas.drawCircle(mDrawableRect.centerX(), mDrawableRect.centerY(), mDrawableRadius, mBitmapPaint);
        if (mBorderWidth > 0) {
            canvas.drawCircle(mBorderRect.centerX(), mBorderRect.centerY(), mBorderRadius, mBorderPaint);
        }
    }

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

    @Override
    public void setPadding(int left, int top, int right, int bottom) {
        super.setPadding(left, top, right, bottom);
        setup();
    }

    @Override
    public void setPaddingRelative(int start, int top, int end, int bottom) {
        super.setPaddingRelative(start, top, end, bottom);
        setup();
    }

    public int getBorderColor() {
        return mBorderColor;
    }

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

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

    /**
     * @deprecated Use {@link #setBorderColor(int)} instead
     */
    @Deprecated
    public void setBorderColorResource(@ColorRes int borderColorRes) {
        setBorderColor(getContext().getResources().getColor(borderColorRes));
    }

    /**
     * Return the color drawn behind the circle-shaped drawable.
     *
     * @return The color drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    public int getFillColor() {
        return mFillColor;
    }

    /**
     * Set a color to be drawn behind the circle-shaped drawable. Note that
     * this has no effect if the drawable is opaque or no drawable is set.
     *
     * @param fillColor The color to be drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    public void setFillColor(@ColorInt int fillColor) {
        if (fillColor == mFillColor) {
            return;
        }

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

    /**
     * Set a color to be drawn behind the circle-shaped drawable. Note that
     * this has no effect if the drawable is opaque or no drawable is set.
     *
     * @param fillColorRes The color resource to be resolved to a color and
     *                     drawn behind the drawable
     *
     * @deprecated Fill color support is going to be removed in the future
     */
    @Deprecated
    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();
    }

    public boolean isDisableCircularTransformation() {
        return mDisableCircularTransformation;
    }

    public void setDisableCircularTransformation(boolean disableCircularTransformation) {
        if (mDisableCircularTransformation == disableCircularTransformation) {
            return;
        }

        mDisableCircularTransformation = disableCircularTransformation;
        initializeBitmap();
    }

    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        initializeBitmap();
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        initializeBitmap();
    }

    @Override
    public void setImageResource(@DrawableRes int resId) {
        super.setImageResource(resId);
        initializeBitmap();
    }

    @Override
    public void setImageURI(Uri uri) {
        super.setImageURI(uri);
        initializeBitmap();
    }

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

        mColorFilter = cf;
        applyColorFilter();
        invalidate();
    }

    @Override
    public ColorFilter getColorFilter() {
        return mColorFilter;
    }

    private void applyColorFilter() {
        if (mBitmapPaint != null) {
            mBitmapPaint.setColorFilter(mColorFilter);
        }
    }

    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 initializeBitmap() {
        if (mDisableCircularTransformation) {
            mBitmap = null;
        } else {
            mBitmap = getBitmapFromDrawable(getDrawable());
        }
        setup();
    }

    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(calculateBounds());
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2.0f, (mBorderRect.width() - mBorderWidth) / 2.0f);

        mDrawableRect.set(mBorderRect);
        if (!mBorderOverlay && mBorderWidth > 0) {
            mDrawableRect.inset(mBorderWidth - 1.0f, mBorderWidth - 1.0f);
        }
        mDrawableRadius = Math.min(mDrawableRect.height() / 2.0f, mDrawableRect.width() / 2.0f);

        applyColorFilter();
        updateShaderMatrix();
        invalidate();
    }

    private RectF calculateBounds() {
        int availableWidth  = getWidth() - getPaddingLeft() - getPaddingRight();
        int availableHeight = getHeight() - getPaddingTop() - getPaddingBottom();

        int sideLength = Math.min(availableWidth, availableHeight);

        float left = getPaddingLeft() + (availableWidth - sideLength) / 2f;
        float top = getPaddingTop() + (availableHeight - sideLength) / 2f;

        return new RectF(left, top, left + sideLength, top + sideLength);
    }

    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);
    }

}

xml使用方式实例：

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:background="@color/color_main"
        android:gravity="center"
        android:orientation="vertical">

        <de.hdodenhof.circleimageview.CircleImageView
            android:id="@+id/profile_image"
            android:layout_width="96dp"
            android:layout_height="96dp"
            android:src="@mipmap/timg"
            app:civ_border_color="@color/color_white"
            app:civ_border_width="2dp" />

</LinearLayout>