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Android自己定义圆角ImageView

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落花踏尽游何处，笑入胡姬酒肆中。这篇文章主要讲述Android自己定义圆角ImageView相关的知识，希望能为你提供帮助。
【Android自己定义圆角ImageView】我们常常看到一些app中能够显示圆角图片。比方qq的联系人图标等等，实现圆角图片一种办法是直接使用圆角图片资源，当然假设没有圆角图片资源。我们也能够自己通过程序实现的，以下介绍一个自己定义圆角ImageView的方法：

package com.yulongfei.imageview; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.PorterDuff; import android.graphics.PorterDuffXfermode; import android.graphics.RectF; import android.util.AttributeSet; import android.widget.ImageView; public class RoundAngleImageView extends ImageView { private int roundWidth = 13; private int roundHeight = 13; public RoundAngleImageView(Context context) { super(context); init(context, null); } public RoundAngleImageView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context, attrs); } public RoundAngleImageView(Context context, AttributeSet attrs) { super(context, attrs); init(context, attrs); } private void init(Context context, AttributeSet attrs) { if (attrs != null) { TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RoundAngleImageView); roundWidth = a.getDimensionPixelSize( R.styleable.RoundAngleImageView_roundWidth, roundWidth); roundHeight = a.getDimensionPixelSize( R.styleable.RoundAngleImageView_roundHeight, roundHeight); a.recycle(); } else { float density = context.getResources().getDisplayMetrics().density; roundWidth = (int)(roundWidth * density); roundHeight = (int)(roundHeight * density); } } /** 重写draw() */ @Override public void draw(Canvas canvas) {//实例化一个和ImageView一样大小的bitmap Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Config.ARGB_8888); //实例化一个canvas，这个canvas相应的内存为上面的bitmap Canvas canvas2 = new Canvas(bitmap); if (bitmap.isRecycled()) { bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Config.ARGB_8888); canvas2 = new Canvas(bitmap); }//将imageView自己绘制到canvas2上，这个导致bitmap里面存放了imageView super.draw(canvas2); //利用canvas画一个圆角矩形，这个会改动bitmap的数据 drawRoundAngle(canvas2); //将裁剪好的bitmap绘制到系统当前canvas上，这样裁剪好的imageview就能显示到屏幕上 Paint paint = new Paint(); paint.setXfermode(null); canvas.drawBitmap(bitmap, 0, 0, paint); bitmap.recycle(); } public void setRoundWidth(int roundWidth, int roundHeight) { this.roundWidth = roundWidth; this.roundHeight = roundHeight; } private void drawRoundAngle(Canvas canvas) { Paint maskPaint = new Paint(); maskPaint.setAntiAlias(true); maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); Path maskPath = new Path(); maskPath.addRoundRect(new RectF(0.0F, 0.0F, getWidth(), getHeight()), roundWidth, roundHeight, Path.Direction.CW); //这是设置了填充模式。很关键 maskPath.setFillType(Path.FillType.INVERSE_WINDING); canvas.drawPath(maskPath, maskPaint); } }





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