android 自定义ImageView显示圆形图片

做个安卓客户端，在个人中心页面要用到一个圆形图片，系统好像没有自带这种样式，得自定义一个ImageView来实现

更多内容可以访问我的个人网站: https://www.cjluzzl.cn
java代码

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;
//这里导入你自己的R文件
//import cn.cjluzzl.tbt.tbtproject.R;

/**
* Created by
* "cjluzzl"
* on 2017/9/18 17:04.
*/

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;
}
}


styles.xml代码
<resources>
<declare-styleable name="CircularImage">
<attr name="border_width" format="dimension" />
<attr name="border_color" format="color" />
</declare-styleable>
</resources>

在layout布局文件中的使用
<你的CircleImageView所在包名.CircleImageView
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/my_launcher2"
/>

这样就实现了一个自定义ImageView。