Android应用中如何将头像图片变圆形

package com.common.base.util;
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.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.util.AttributeSet;
import android.widget.ImageView;
import com.common.base.R;
public class CircleImageView extends ImageView {
 /**
  * 头像转换工具类
  */
 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 = 1;
 private static final int DEFAULT_BORDER_WIDTH = 0;
 private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
 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 int mBorderColor = DEFAULT_BORDER_COLOR;
 private int mBorderWidth = DEFAULT_BORDER_WIDTH;
 private Bitmap mBitmap;
 private BitmapShader mBitmapShader;
 private int mBitmapWidth;
 private int mBitmapHeight;
 private float mDrawableRadius;
 private float mBorderRadius;
 private boolean mReady;
 private boolean mSetupPending;
 public CircleImageView(Context context) {
  super(context);
 }
 public CircleImageView(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
 }
 public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  super.setScaleType(SCALE_TYPE);
  TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);
  mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
  mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR);
  a.recycle();
  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
 protected void onDraw(Canvas canvas) {
  if (getDrawable() == null) {
   return;
  }
  canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint);
  canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius, mBorderPaint);
 }
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  setup();
 }
 public int getBorderColor() {
  return mBorderColor;
 }
 public void setBorderColor(int borderColor) {
  if (borderColor == mBorderColor) {
   return;
  }
  mBorderColor = borderColor;
  mBorderPaint.setColor(mBorderColor);
  invalidate();
 }
 public int getBorderWidth() {
  return mBorderWidth;
 }
 public void setBorderWidth(int borderWidth) {
  if (borderWidth == mBorderWidth) {
   return;
  }
  mBorderWidth = borderWidth;
  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(int resId) {
  super.setImageResource(resId);
  mBitmap = getBitmapFromDrawable(getDrawable());
  setup();
 }
 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 (OutOfMemoryError e) {
   return null;
  }
 }
 private void setup() {
  if (!mReady) {
   mSetupPending = true;
   return;
  }
  if (mBitmap == null) {
   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);
  mBitmapHeight = mBitmap.getHeight();
  mBitmapWidth = mBitmap.getWidth();
  mBorderRect.set(0, 0, getWidth(), getHeight());
  mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2);
  mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width() - mBorderWidth, mBorderRect.height() - mBorderWidth);
  mDrawableRadius = Math.min(mDrawableRect.height() / 2, mDrawableRect.width() / 2);
  updateShaderMatrix();
  invalidate();
 }
 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) + mBorderWidth, (int) (dy + 0.5f) + mBorderWidth);
  mBitmapShader.setLocalMatrix(mShaderMatrix);
 }
}

<com.common.base.util.CircleImageView
 android:id="@+id/touxian_id"
 android:layout_width="75dp"
 android:layout_height="75dp"
 android:layout_centerHorizontal="true"
 android:layout_centerVertical="true"
 android:src="@drawable/yonghu_touxiang" />

private CircleImageView touxiang_id;
touxiang_id = (CircleImageView)findViewById(R.id.touxian_id)
BitmapHelp.displayOnImageView(mContext, holder.touxiang_id, mListy
  .getUser().getPic(), R.drawable.ic_launcher,
  R.drawable.ic_launcher);