Android ImageView绘制圆角效果
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; } }
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。
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