关于Android圆形图片的一种优化方案（可以显示网络图片）

在Android App中，我们经常看到圆形头像图片，然后网上也有很多开源的控件。刚好这个项目用到了，也去找了一些开源的，发现并不完美，所以只好自己优化了，废话不多说，先上效果图：

下面是源码：本人能理解的地方都加上注释了，大牛勿喷。

package com.xyt.ygcf.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.graphics.Xfermode;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.NinePatchDrawable;
import android.util.AttributeSet;
import android.widget.ImageView;

import com.xyt.yangguangchufang.R;

public class CircleImageView extends ImageView {

	private static final Xfermode MASK_XFERMODE;
	private Bitmap mask;
	private Paint paint;
	private int mBorderWidth = 10;
	private int mBorderColor = Color.parseColor("#f2f2f2");

	static {
		PorterDuff.Mode localMode = PorterDuff.Mode.DST_IN;
		MASK_XFERMODE = new PorterDuffXfermode(localMode);
	}

	public CircleImageView(Context paramContext) {
		super(paramContext);
	}

	public CircleImageView(Context paramContext, AttributeSet paramAttributeSet) {
		this(paramContext, paramAttributeSet, 0);
	}

	public CircleImageView(Context paramContext, AttributeSet paramAttributeSet, int paramInt) {
		super(paramContext, paramAttributeSet, paramInt);
		TypedArray a = paramContext.obtainStyledAttributes(paramAttributeSet, R.styleable.CircularImage);
		mBorderColor = a.getColor(R.styleable.CircularImage_border_color, mBorderColor);
		final int defalut = (int) (2 * paramContext.getResources().getDisplayMetrics().density + 0.5f);
		mBorderWidth = a.getDimensionPixelOffset(R.styleable.CircularImage_border_width, defalut);
		a.recycle();
	}

	private boolean useDefaultStyle = false;

	public void setUseDefaultStyle(boolean useDefaultStyle) {
		this.useDefaultStyle = useDefaultStyle;
	}

	@Override
	protected void onDraw(Canvas paramCanvas) {
		if (useDefaultStyle) {
			super.onDraw(paramCanvas);
			return;
		}
		final Drawable localDrawable = getDrawable();
		if (localDrawable == null)
			return;
		if (localDrawable instanceof NinePatchDrawable) {
			return;
		}
		if (this.paint == null) {
			final Paint localPaint = new Paint();
			localPaint.setFilterBitmap(false);
			localPaint.setAntiAlias(true);
			localPaint.setXfermode(MASK_XFERMODE);
			this.paint = localPaint;
		}
		final int width = getWidth();
		final int height = getHeight();
		/** 保存layer */
		int layer = paramCanvas.saveLayer(0.0F, 0.0F, width, height, null, 31);
		/** 设置drawable的大小 */
		localDrawable.setBounds(0, 0, width, height);
		/** 将drawable绑定到bitmap(this.mask)上面（drawable只能通过bitmap显示出来） */
		localDrawable.draw(paramCanvas);
		if ((this.mask == null) || (this.mask.isRecycled())) {
			this.mask = createOvalBitmap(width, height);
		}
		/** 将bitmap画到canvas上面 */
		paramCanvas.drawBitmap(this.mask, 0.0F, 0.0F, this.paint);
		/** 将画布复制到layer上 */
		paramCanvas.restoreToCount(layer);
		drawBorder(paramCanvas, width, height);
	}

	/**
	 * 绘制最外面的边框
	 * 
	 * @param canvas
	 * @param width
	 * @param height
	 */
	private void drawBorder(Canvas canvas, final int width, final int height) {
		if (mBorderWidth == 0) {
			return;
		}
		final Paint mBorderPaint = new Paint();
		mBorderPaint.setStyle(Paint.Style.STROKE);
		mBorderPaint.setAntiAlias(true);
		mBorderPaint.setColor(mBorderColor);
		mBorderPaint.setStrokeWidth(mBorderWidth);
		/**
		 * 坐标x：view宽度的一般 坐标y：view高度的一般 半径r：因为是view的宽度-border的一半
		 */
		canvas.drawCircle(width >> 1, height >> 1, (width - mBorderWidth) >> 1, mBorderPaint);
		canvas = null;
	}

	/**
	 * 获取一个bitmap，目的是用来承载drawable;
	 * <p>
	 * 将这个bitmap放在canvas上面承载，并在其上面画一个椭圆(其实也是一个圆，因为width=height)来固定显示区域
	 * 
	 * @param width
	 * @param height
	 * @return
	 */
	public Bitmap createOvalBitmap(final int width, final int height) {
		Bitmap.Config localConfig = Bitmap.Config.ARGB_8888;
		Bitmap localBitmap = Bitmap.createBitmap(width, height, localConfig);
		Canvas localCanvas = new Canvas(localBitmap);
		Paint localPaint = new Paint();
		final int padding = mBorderWidth - 3;
		/**
		 * 设置椭圆的大小(因为椭圆的最外边会和border的最外边重合的，如果图片最外边的颜色很深，有看出有棱边的效果，所以为了让体验更加好，
		 * 让其缩进padding px)
		 */
		RectF localRectF = new RectF(padding, padding, width - padding, height - padding);
		localCanvas.drawOval(localRectF, localPaint);
		return localBitmap;
	}
}

xml布局：

<com.xyt.ygcf.widget.CircleImageView
        xmlns:myxmlns="http://schemas.android.com/apk/res/com.xyt.yangguangchufang"
        android:id="@+id/fragment_my_image_user"
        android:layout_width="110dp"
        android:layout_height="110dp"
        android:layout_marginBottom="10dp"
        android:contentDescription="@null"
        android:scaleType="centerCrop"
        myxmlns:border_width="@dimen/circle_width"
        myxmlns:border_color="@color/f2f2f2"
        android:src="@drawable/ic_my_avar_unlogin" />

attr文件：

 <declare-styleable name="CircularImage">
        <attr name="border_width" format="dimension" />
        <attr name="border_color" format="color" />
    </declare-styleable>

抽空还要认真研究一下canvas，理解还不是太深刻。