怎么在Android中利用ImageView控件实现一个圆角功能

本文讲解"如何在Android中利用ImageView控件实现一个圆角功能"，希望能够解决相关问题。

1.创建CustomImageView 类在你的项目中(源码如下)

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;

import com.towatt.charge.towatt.R;

/**
* @author Mr.lynn
* @version 1.0<br>
* 图片圆角实现
*/
public class CustomImageView extends android.support.v7.widget.AppCompatImageView {
private Paint paint;
private Paint paintBorder;
private Bitmap mSrcBitmap;
/**
* 圆角的弧度
*/
private float mRadius;
private boolean mIsCircle;

public CustomImageView(final Context context) {
this(context, null);
}

public CustomImageView(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.customImageViewStyle);
}

public CustomImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray ta = context.obtainStyledAttributes(attrs,
  R.styleable.CustomImageView, defStyle, 0);
mRadius = ta.getDimension(R.styleable.CustomImageView_radius, 0);
mIsCircle = ta.getBoolean(R.styleable.CustomImageView_circle, false);
int srcResource = attrs.getAttributeResourceValue(
  "http://schemas.android.com/apk/res/android", "src", 0);
if (srcResource != 0)
 mSrcBitmap = BitmapFactory.decodeResource(getResources(),
   srcResource);
ta.recycle();
paint = new Paint();
paint.setAntiAlias(true);
paintBorder = new Paint();
paintBorder.setAntiAlias(true);
}

@Override
public void onDraw(Canvas canvas) {
int width = canvas.getWidth() - getPaddingLeft() - getPaddingRight();
int height = canvas.getHeight() - getPaddingTop() - getPaddingBottom();
Bitmap image = drawableToBitmap(getDrawable());
if (mIsCircle) {
 Bitmap reSizeImage = reSizeImageC(image, width, height);
 canvas.drawBitmap(createCircleImage(reSizeImage, width, height),
   getPaddingLeft(), getPaddingTop(), null);

} else {

 Bitmap reSizeImage = reSizeImage(image, width, height);
 canvas.drawBitmap(createRoundImage(reSizeImage, width, height),
   getPaddingLeft(), getPaddingTop(), null);
}
}

/**
* 画圆角
*
* @param source
* @param width
* @param height
* @return
*/
private Bitmap createRoundImage(Bitmap source, int width, int height) {
Paint paint = new Paint();
paint.setAntiAlias(true);
Bitmap target = Bitmap.createBitmap(width, height, Config.ARGB_8888);
Canvas canvas = new Canvas(target);
RectF rect = new RectF(0, 0, width, height);
canvas.drawRoundRect(rect, mRadius, mRadius, paint);
// 核心代码取两个图片的交集部分
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(source, 0, 0, paint);
return target;
}

/**
* 画圆
*
* @param source
* @param width
* @param height
* @return
*/
private Bitmap createCircleImage(Bitmap source, int width, int height) {

Paint paint = new Paint();
paint.setAntiAlias(true);
Bitmap target = Bitmap.createBitmap(width, height, Config.ARGB_8888);
Canvas canvas = new Canvas(target);
canvas.drawCircle(width / 2, height / 2, Math.min(width, height) / 2,
  paint);
// 核心代码取两个图片的交集部分
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(source, (width - source.getWidth()) / 2,
  (height - source.getHeight()) / 2, paint);
return target;

}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = MeasureSpec.getSize(widthMeasureSpec);
int height = MeasureSpec.getSize(heightMeasureSpec);
setMeasuredDimension(width, height);
}

/**
* drawable转bitmap
*
* @param drawable
* @return
*/
private Bitmap drawableToBitmap(Drawable drawable) {
if (drawable == null) {
 if (mSrcBitmap != null) {
  return mSrcBitmap;
 } else {
  return null;
 }
} else if (drawable instanceof BitmapDrawable) {
 return ((BitmapDrawable) drawable).getBitmap();
}
Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),
  drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
}

/**
* 重设Bitmap的宽高
*
* @param bitmap
* @param newWidth
* @param newHeight
* @return
*/
private Bitmap reSizeImage(Bitmap bitmap, int newWidth, int newHeight) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
// 计算出缩放比
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
// 矩阵缩放bitmap
Matrix matrix = new Matrix();

matrix.postScale(scaleWidth, scaleHeight);
return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
}

/**
* 重设Bitmap的宽高
*
* @param bitmap
* @param newWidth
* @param newHeight
* @return
*/
private Bitmap reSizeImageC(Bitmap bitmap, int newWidth, int newHeight) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
int x = (newWidth - width) / 2;
int y = (newHeight - height) / 2;
if (x > 0 && y > 0) {
 return Bitmap.createBitmap(bitmap, 0, 0, width, height, null, true);
}

float scale = 1;

if (width > height) {
 // 按照宽度进行等比缩放
 scale = ((float) newWidth) / width;

} else {
 // 按照高度进行等比缩放
 // 计算出缩放比
 scale = ((float) newHeight) / height;
}
Matrix matrix = new Matrix();
matrix.postScale(scale, scale);
return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
}
}

2.在values目录下创建attrs.xml(若是已存在该文件)直接复制如下代码既可

<resources>
<declare-styleable name="Theme">
<attr name="customImageViewStyle" format="reference" />
</declare-styleable>
<!-- 自定义圆角ImageView -->
<declare-styleable name="CustomImageView">
<attr name="circle" format="boolean" />
<attr name="radius" format="dimension" />
</declare-styleable>
</resources>

3.正确的使用方式(在布局文件中)

注意此路径是你控件所在包

 <com.xxx.xxx.view.CustomImageView
android:layout_marginTop="5dp"
android:layout_width="77dp"
android:layout_height="77dp"
lynn:radius="@dimen/size_10dp"
android:src="@drawable/position_icon"
android:id="@+id/iv_build_icon" />

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