Android ImageView绘制圆角效果

2019-12-12 04:09:52

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来源：转载

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前言

Android 开发中，我们经常需要实现图片的圆形/圆角的效果，我们可以使用两种方式来实现这样的效果。一种是使用Xfermode，另一种是BitmapShader来实现。下面我将分别介绍这两种用法。

使用Xfermode的方式实现
使用该方式的关键代码，如下：

  private Bitmap creataBitmap(Bitmap bitmap) {    //用指定的一个Bitmap来构建一个画布    Bitmap target = Bitmap.createBitmap(1000,1000, Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(target);    final Paint paint = new Paint();    paint.setColor(Color.GREEN);    paint.setAntiAlias(true);    //在刚才的画布上绘制一个圆形区域    canvas.drawCircle(500,500,500,paint);    //设置Xfermode，使用SRC_IN模式,这样可以取到第二张图片重叠后的区域    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));    //在画布上绘制第二个需要显示的bitmap    canvas.drawBitmap(bitmap,0,0,paint);    return target;  }

上面代码中看出在指定的画布上绘制了两层图像，一个是半径为500像素的圆形，一个是将目标Bitmap绘制在上面。之间还调用了paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));作用是这两个绘制的效果图叠加后，取得第二个图的交集图。所以，我们先绘制一个圆形，然后绘制Bitmap，交集为圆形，取出的就是圆形区域的Bitmap了。
PorterDuff.Mode中一共有16种效果显示，如下：

可以根据不同的Mode，控制显示的效果图。

开始应用

1.自定义属性在attrs.xml中

<?xml version="1.0" encoding="utf-8"?><resources>  <attr name="borderRadius" format="dimension" />  <attr name="type">    <enum name="circle" value="0"/>    <enum name="round" value="1"/>  </attr>  <attr name="src" format="reference"/>  <declare-styleable name="RoundImageView">    <attr name="borderRadius"/>    <attr name="type"/>    <attr name="src"/>  </declare-styleable></resources>

2.自定义View

public class RoundImageView extends View {  private int type;  private static final int TYPE_CIRCLE = 0;  private static final int TYPE_ROUND = 1;  //图片  private Bitmap mSrc;  //圆角大小  private int mRadius;  //高度  private int mWidth;  //宽度  private int mHeight;  public RoundImageView(Context context, AttributeSet attrs) {    super(context, attrs);    //获取自定义的属性    TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.RoundImageView);    //获取自定以属性的数目    int count = a.getIndexCount();    for (int i=0 ; i<count ; i++){      int attr = a.getIndex(i);      switch (attr){        case R.styleable.RoundImageView_borderRadius:          int defValue = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,10f,getResources().getDisplayMetrics());          mRadius = a.getDimensionPixelSize(attr, defValue);          break;        case R.styleable.RoundImageView_type:          type = a.getInt(attr,0);          break;        case R.styleable.RoundImageView_src:          mSrc = BitmapFactory.decodeResource(getResources(),a.getResourceId(attr,0));          break;      }    }    a.recycle();  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    //设置宽度    int specMode = MeasureSpec.getMode(widthMeasureSpec);    int specSize = MeasureSpec.getSize(widthMeasureSpec);    if (specMode == MeasureSpec.EXACTLY){      mWidth = specSize;    }else {      int desireByImg = getPaddingLeft() + getPaddingRight() + mSrc.getWidth();      if (specMode == MeasureSpec.AT_MOST)// wrap_content      {        mWidth = Math.min(desireByImg, specSize);      } else        mWidth = desireByImg;    }    //设置高度    specMode = MeasureSpec.getMode(heightMeasureSpec);    specSize = MeasureSpec.getSize(heightMeasureSpec);    if (specMode == MeasureSpec.EXACTLY){      mHeight = specSize;    }else {      int desire = getPaddingTop() + getPaddingBottom() + mSrc.getHeight();      if (specMode == MeasureSpec.AT_MOST)// wrap_content      {        mHeight = Math.min(desire, specSize);      } else        mHeight = desire;    }    setMeasuredDimension(mWidth,mHeight);  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    switch (type){      case TYPE_CIRCLE:        int min = Math.min(mWidth,mHeight);        //从当前存在的Bitmap，按一定的比例创建一个新的Bitmap。        mSrc = Bitmap.createScaledBitmap(mSrc, min, min, false);        canvas.drawBitmap(createCircleImage(mSrc, min), 0, 0, null);        break;      case TYPE_ROUND:        mSrc = Bitmap.createScaledBitmap(mSrc, mWidth, mHeight, false);        canvas.drawBitmap(createRoundConerImage(mSrc), 0, 0, null);        break;    }  }  /**   * 绘制圆角   * @param source   * @return   */  private Bitmap createRoundConerImage(Bitmap source) {    final Paint paint = new Paint();    paint.setAntiAlias(true);    Bitmap target = Bitmap.createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(target);    RectF rect = new RectF(0, 0, mWidth, mHeight);    canvas.drawRoundRect(rect, mRadius, mRadius, paint);    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));    canvas.drawBitmap(source, 0, 0, paint);    return target;  }  /**   * 绘制圆形   * @param source   * @param min   * @return   */  private Bitmap createCircleImage(Bitmap source, int min) {    final Paint paint = new Paint();    paint.setAntiAlias(true);    Bitmap target = Bitmap.createBitmap(min, min, Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(target);    canvas.drawCircle(min/2,min/2,min/2,paint);    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));    canvas.drawBitmap(source, 0, 0, paint);    return target;  }}

3.布局文件

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"       xmlns:roundview="http://schemas.android.com/apk/res-auto"       xmlns:tools="http://schemas.android.com/tools"       android:id="@+id/activity_main"       android:layout_width="match_parent"       android:layout_height="match_parent"       android:orientation="vertical"       android:padding="10dp"       tools:context="mo.yumf.com.myviews.MainActivity">  <mo.yumf.com.myviews.RoundImageView    android:layout_width="200dp"    android:layout_height="200dp"    android:layout_marginTop="20dp"    roundview:borderRadius="10dp"    roundview:src="@drawable/ac_default_icon"    roundview:type="round"/>  <mo.yumf.com.myviews.RoundImageView    android:layout_width="200dp"    android:layout_height="200dp"    android:layout_marginTop="20dp"    roundview:src="@drawable/ac_default_icon"    roundview:type="circle"/></LinearLayout>

上面的自定义View中，存在一个局限，那就是只能在布局中设置要加载的图片资源，不能在代码中设置图片。下面我们使用同样的方式，选择自定义ImageView来实现。

public class RoundImageView extends ImageView {  private int type;  private static final int TYPE_CIRCLE = 0;  private static final int TYPE_ROUND = 1;  //图片  private Bitmap mSrc;  //圆角大小  private int mRadius;  public RoundImageView(Context context, AttributeSet attrs) {    super(context, attrs);    //获取自定义的属性    TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.RoundImageView);    //获取自定以属性的数目    int count = a.getIndexCount();    for (int i=0 ; i<count ; i++){      int attr = a.getIndex(i);      switch (attr){        case R.styleable.RoundImageView_borderRadius:          int defValue = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,10f,getResources().getDisplayMetrics());          mRadius = a.getDimensionPixelSize(attr, defValue);          break;        case R.styleable.RoundImageView_type:          type = a.getInt(attr,0);          break;      }    }    a.recycle();  }  @Override  protected void onDraw(Canvas canvas) {    if (getDrawable() != null){      Bitmap bitmap = getBitmap(getDrawable());      if (bitmap != null){        switch (type){          case TYPE_CIRCLE:            //获取ImageView中的宽高，取最小值            int min = Math.min(getMeasuredWidth(),getMeasuredHeight());            //从当前存在的Bitmap，按一定的比例创建一个新的Bitmap。            mSrc = Bitmap.createScaledBitmap(bitmap, min, min, false);            canvas.drawBitmap(createCircleImage(mSrc, min), 0, 0, null);            break;          case TYPE_ROUND:            mSrc = Bitmap.createScaledBitmap(bitmap, getMeasuredWidth(), getMeasuredHeight(), false);            canvas.drawBitmap(createRoundConerImage(mSrc), 0, 0, null);            break;        }      }    }else {      super.onDraw(canvas);    }  }  private Bitmap getBitmap(Drawable drawable) {    if (drawable instanceof BitmapDrawable){      return ((BitmapDrawable)drawable).getBitmap();    }else if (drawable instanceof ColorDrawable){      Rect rect = drawable.getBounds();      int width = rect.right - rect.left;      int height = rect.bottom - rect.top;      int color = ((ColorDrawable)drawable).getColor();      Bitmap bitmap = Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_8888);      Canvas canvas = new Canvas(bitmap);      canvas.drawARGB(Color.alpha(color),Color.red(color), Color.green(color), Color.blue(color));      return bitmap;    }else {      return null;    }  }  /**   * 绘制圆角   * @param source   * @return   */  private Bitmap createRoundConerImage(Bitmap source) {    final Paint paint = new Paint();    paint.setAntiAlias(true);    Bitmap target = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(), Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(target);    RectF rect = new RectF(0, 0, getMeasuredWidth(), getMeasuredHeight());    canvas.drawRoundRect(rect, mRadius, mRadius, paint);    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));    canvas.drawBitmap(source, 0, 0, paint);    return target;  }  /**   * 绘制圆形   * @param source   * @param min   * @return   */  private Bitmap createCircleImage(Bitmap source, int min) {    final Paint paint = new Paint();    paint.setAntiAlias(true);    Bitmap target = Bitmap.createBitmap(min, min, Bitmap.Config.ARGB_8888);    Canvas canvas = new Canvas(target);    canvas.drawCircle(min/2,min/2,min/2,paint);    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));    canvas.drawBitmap(source, 0, 0, paint);    return target;  }}

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