让图片变成圆形

       只有三步

1、创建一个Java类CircleImageView把下面的代码复制过去，报错的导包

package de.hdodenhof.circleimageview;
import edu.njupt.zhb.main.R;
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;

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 = 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);
  }

}

2、在values文件夹下面创建一个xlm文件attrs.xml把下面的代码复制进去

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <declare-styleable name="CircleImageView">
    <attr name="border_width" format="dimension" />
    <attr name="border_color" format="color" />
  </declare-styleable>
</resources>

 3.直接在布局文件中使用  插入你想要的图片

<RelativeLayout
　　xmlns:android="http://schemas.android.com/apk/res/android"
　　xmlns:tools="http://schemas.android.com/tools"
　　android:layout_width="match_parent"
　　android:layout_height="match_parent"
　　android:background="#ff00ff"
>

<com.wang.CircleImageView
　　android:id="@+id/imageview"
　　android:layout_width="100dp"
　　android:layout_height="100dp"
　　android:layout_centerInParent="true"
　　android:src="@drawable/a0a"
/>
</RelativeLayout>