ImageView在我们的项目中经常使用，一般ImageView是正方形的，要使用圆形的ImageView可以通过自定义View来实现，下面我们介绍一下如何实现。
1.CircularImageView.java 继承自ImageView:
package com.yayun.circularimageview;
import com.mikhaellopez.circularimageview.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.Paint;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;
public class CircularImageView extends ImageView {
private int borderWidth;
private int canvasSize;
private Bitmap image;
private Paint paint;
private Paint paintBorder;
public CircularImageView(final Context context) {
this(context, null);
}
public CircularImageView(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.circularImageViewStyle);
}
public CircularImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// init paint
paint = new Paint();
paint.setAntiAlias(true);
paintBorder = new Paint();
paintBorder.setAntiAlias(true);// 抗锯齿
TypedArray attributes = context.obtainStyledAttributes(attrs,
R.styleable.CircularImageView, defStyle, 0);
/**
* 有边框
*/
if (attributes.getBoolean(R.styleable.CircularImageView_border, true)) {
int defaultBorderSize = (int) (4 * getContext().getResources()
.getDisplayMetrics().density + 0.5f);// 默认宽度
setBorderWidth(attributes.getDimensionPixelOffset(
R.styleable.CircularImageView_border_width,
defaultBorderSize));// 边框大小
setBorderColor(attributes.getColor(
R.styleable.CircularImageView_border_color, Color.WHITE));// 边框颜色
}
/**
* 无边框
*/
if (attributes.getBoolean(R.styleable.CircularImageView_shadow, false))
addShadow();
}
/**
* 设置边框宽度
*
* @param borderWidth
*/
public void setBorderWidth(int borderWidth) {
this.borderWidth = borderWidth;
this.requestLayout();
this.invalidate();
}
/**
* 设置边框颜色
*
* @param borderColor
*/
public void setBorderColor(int borderColor) {
if (paintBorder != null)
paintBorder.setColor(borderColor);
this.invalidate();
}
public void addShadow() {
setLayerType(LAYER_TYPE_SOFTWARE, paintBorder);
paintBorder.setShadowLayer(4.0f, 0.0f, 2.0f, Color.BLACK);
}
@Override
public void onDraw(Canvas canvas) {
// load the bitmap
image = drawableToBitmap(getDrawable());
if (image != null) {
canvasSize = canvas.getWidth();
if (canvas.getHeight() < canvasSize)// 取小值
canvasSize = canvas.getHeight();
BitmapShader shader = new BitmapShader(Bitmap.createScaledBitmap(
image, canvasSize, canvasSize, false),
Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
paint.setShader(shader);
/**
* 圆心
*/
int circleCenter = (canvasSize - (borderWidth * 2)) / 2;
// void android.graphics.Canvas.drawCircle(float cx, float cy, float radius, Paint paint)
canvas.drawCircle(circleCenter + borderWidth, circleCenter
+ borderWidth, ((canvasSize - (borderWidth * 2)) / 2)
+ borderWidth - 4.0f, paintBorder);
canvas.drawCircle(circleCenter + borderWidth, circleCenter
+ borderWidth,
((canvasSize - (borderWidth * 2)) / 2) - 4.0f, paint);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = measureWidth(widthMeasureSpec);
int height = measureHeight(heightMeasureSpec);
setMeasuredDimension(width, height);
}
private int measureWidth(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
// The parent has determined an exact size for the child.
result = specSize;
} else if (specMode == MeasureSpec.AT_MOST) {
// The child can be as large as it wants up to the specified size.
result = specSize;
} else {
// The parent has not imposed any constraint on the child.
result = canvasSize;
}
return result;
}
private int measureHeight(int measureSpecHeight) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpecHeight);
int specSize = MeasureSpec.getSize(measureSpecHeight);
if (specMode == MeasureSpec.EXACTLY) {
// We were told how big to be
result = specSize;
} else if (specMode == MeasureSpec.AT_MOST) {
// The child can be as large as it wants up to the specified size.
result = specSize;
} else {
// Measure the text (beware: ascent is a negative number)
result = canvasSize;
}
return (result + 2);
}
/**
* 获取bitmap
*
* @param drawable
* @return
*/
public Bitmap drawableToBitmap(Drawable drawable) {
if (drawable == null) {
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;
}
}知识：一般来说，自定义控件都会去重写View的onMeasure方法，因为该方法指定该控件在屏幕上的大小。
protected void?onMeasure?(int widthMeasureSpec, int heightMeasureSpec)
onMeasure传入的两个参数是由上一层控件传入的大小，有多种情况，重写该方法时需要对计算控件的实际大小，然后调用setMeasuredDimension(int, int)设置实际大小。
onMeasure传入的widthMeasureSpec和heightMeasureSpec不是一般的尺寸数值，而是将模式和尺寸组合在一起的数值。我们需要通过int mode = MeasureSpec.getMode(widthMeasureSpec)得到模式，用int size =?MeasureSpec.getSize(widthMeasureSpec)得到尺寸。
mode共有三种情况，取值分别为
MeasureSpec.UNSPECIFIED, MeasureSpec.EXACTLY, MeasureSpec.AT_MOST。
MeasureSpec.EXACTLY是精确尺寸，当我们将控件的layout_width或layout_height指定为具体数值时如andorid:layout_width="50dip"，或者为FILL_PARENT是，都是控件大小已经确定的情况，都是精确尺寸。
MeasureSpec.AT_MOST是最大尺寸，当控件的layout_width或layout_height指定为WRAP_CONTENT时，控件大小一般随着控件的子空间或内容进行变化，此时控件尺寸只要不超过父控件允许的最大尺寸即可。因此，此时的mode是AT_MOST，size给出了父控件允许的最大尺寸。
MeasureSpec.UNSPECIFIED是未指定尺寸，这种情况不多，一般都是父控件是AdapterView，通过measure方法传入的模式。
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="CircularImageView">
<attr name="border" format="boolean"></attr>
<attr name="border_width" format="dimension"></attr>
<attr name="border_color" format="color"></attr>
<attr name="shadow" format="boolean"></attr>
</declare-styleable>
<declare-styleable name="Theme">
<attr name="circularImageViewStyle" format="reference"></attr>
</declare-styleable>
</resources><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res/com.mikhaellopez.circularimageviewsample"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center"
android:orientation="vertical" >
<com.yayun.circularimageview.CircularImageView
android:layout_width="250dp"
android:layout_height="250dp"
android:src="@drawable/image"
app:border="true"
app:border_color="@color/Blue"
app:border_width="14dp"
app:shadow="true" />
<com.yayun.circularimageview.CircularImageView
android:layout_width="200dp"
android:layout_height="200dp"
android:src="@drawable/image"
/>
</LinearLayout>
第一个图片有边框的效果，可以自行设置。
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版权声明：本文为博主原创文章，未经博主允许不得转载。
Android实战简易教程-第六十一枪（圆形显示的ImageView）
原文：http://blog.csdn.net/yayun0516/article/details/48628231