Android 完美实现图片圆角和圆形

2021-10-19 09:16:37

本来想在网上找个圆角的例子看一看，不尽人意啊，基本都是官方的Demo的那张原理图，稍后会贴出。于是自己自定义了个View，实现图片的圆角以及圆形效果。效果图：

好了，原理和核心代码解释完成。下面开始写自定义View。

1、自定义属性：

第一个是原图，第二个是圆形效果，第三第四设置了不同的圆角大小。

准备改变一个博客的风格，首先给大家讲一下原理，让大家明白了，然后再贴代码，不然可以直接看那么长的代码也比较痛苦，核心代码其实就那么几行：

核心代码分析：

/**
* 绘制
*/
@Override
protected void onDraw(Canvas canvas)
{
switch (type)
{
// 如果是TYPE_CIRCLE绘制圆形
case TYPE_CIRCLE:
int min = Math.min(mWidth, mHeight);
/**
* 长度如果不一致，按小的值进行压缩
*/
mSrc = Bitmap.createScaledBitmap(mSrc, min, min, false);
canvas.drawBitmap(createCircleImage(mSrc, min), 0, 0, null);
break;
case TYPE_ROUND:
canvas.drawBitmap(createRoundConerImage(mSrc), 0, 0, null);
break;
}
}
/**
* 根据原图和变长绘制圆形图片
*
* @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, Config.ARGB_8888);
/**
* 产生一个同样大小的画布
*/
Canvas canvas = new Canvas(target);
/**
* 首先绘制圆形
*/
canvas.drawCircle(min / 2, min / 2, min / 2, paint);
/**
* 使用SRC_IN，参考上面的说明
*/
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
/**
* 绘制图片
*/
canvas.drawBitmap(source, 0, 0, paint);
return target;
}
/**
* 根据原图添加圆角
*
* @param source
* @return
*/
private Bitmap createRoundConerImage(Bitmap source)
{
final Paint paint = new Paint();
paint.setAntiAlias(true);
Bitmap target = Bitmap.createBitmap(mWidth, mHeight, Config.ARGB_8888);
Canvas canvas = new Canvas(target);
RectF rect = new RectF(0, 0, source.getWidth(), source.getHeight());
canvas.drawRoundRect(rect, mRadius, mRadius, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(source, 0, 0, paint);
return target;
}

/**
* 计算控件的高度和宽度
*/
@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)// match_parent , accurate
{
mWidth = specSize;
} else
{
// 由图片决定的宽
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)// match_parent , accurate
{
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);
}

4、根据Type绘制：

[java] view plain copy

/**
* TYPE_CIRCLE / TYPE_ROUND
*/
private int type;
private static final int TYPE_CIRCLE = 0;
private static final int TYPE_ROUND = 1;
/**
* 图片
*/
private Bitmap mSrc;
/**
* 圆角的大小
*/
private int mRadius;
/**
* 控件的宽度
*/
private int mWidth;
/**
* 控件的高度
*/
private int mHeight;
public CustomImageView(Context context, AttributeSet attrs)
{
this(context, attrs, 0);
}
public CustomImageView(Context context)
{
this(context, null);
}
/**
* 初始化一些自定义的参数
*
* @param context
* @param attrs
* @param defStyle
*/
public CustomImageView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyle, 0);
int n = a.getIndexCount();
for (int i = 0; i < n; i++)
{
int attr = a.getIndex(i);
switch (attr)
{
case R.styleable.CustomImageView_src:
mSrc = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
break;
case R.styleable.CustomImageView_type:
type = a.getInt(attr, 0);// 默认为Circle
break;
case R.styleable.CustomImageView_borderRadius:
mRadius= a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10f,
getResources().getDisplayMetrics()));// 默认为10DP
break;
}
}
a.recycle();
}

3、onMeasure中获取控件宽高：

[java] view plain copy

<?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"></attr>
<declare-styleable name="CustomImageView">
<attr name="borderRadius" />
<attr name="type" />
<attr name="src" />
</declare-styleable>
</resources>

2、构造中获取自定义的属性：

[java] view plain copy

canvas.translate(x, y);
canvas.drawBitmap(mDstB, 0, 0, paint);
paint.setXfermode(sModes[i]);
canvas.drawBitmap(mSrcB, 0, 0, paint);
paint.setXfermode(null);
canvas.restoreToCount(sc);

可以看出先绘制的Dst,再绘制的Src，最后的展示是SrcIn那个图：显示的区域是二者交集，展示的是Src(后者)。和咱们前面结论一致。效果16种，大家可以*组合展示不同的效果。

好了，原理和核心代码解释完成。下面开始写自定义View。

1、自定义属性：

[html] view plain copy

/**
* 根据原图和变长绘制圆形图片
*
* @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, Config.ARGB_8888);
/**
* 产生一个同样大小的画布
*/
Canvas canvas = new Canvas(target);
/**
* 首先绘制圆形
*/
canvas.drawCircle(min / 2, min / 2, min / 2, paint);
/**
* 使用SRC_IN
*/
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
/**
* 绘制图片
*/
canvas.drawBitmap(source, 0, 0, paint);
return target;
}

其实主要靠：paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));这行代码，为什么呢，我给大家解释下，SRC_IN这种模式，两个绘制的效果叠加后取交集展现后图，怎么说呢，咱们第一个绘制的是个圆形，第二个绘制的是个Bitmap，于是交集为圆形，展现的是BItmap，就实现了圆形图片效果。圆角，其实就是先绘制圆角矩形，是不是很简单，以后别人再说实现圆角，你就把这一行代码给他就行了。

从Android的示例中，给大家证明一下：

下面有一张PorterDuff.Mode的16中效果图，咱们的只是其一：

源码咱们只关心谁先谁后绘制的：

canvas.translate(x, y);
canvas.drawBitmap(mDstB, 0, 0, paint);
paint.setXfermode(sModes[i]);
canvas.drawBitmap(mSrcB, 0, 0, paint);
paint.setXfermode(null);
canvas.restoreToCount(sc);

<?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"></attr>
<declare-styleable name="CustomImageView">
<attr name="borderRadius" />
<attr name="type" />
<attr name="src" />
</declare-styleable>
</resources>

2、构造中获取自定义的属性：

/**
* TYPE_CIRCLE / TYPE_ROUND
*/
private int type;
private static final int TYPE_CIRCLE = 0;
private static final int TYPE_ROUND = 1;
/**
* 图片
*/
private Bitmap mSrc;
/**
* 圆角的大小
*/
private int mRadius;
/**
* 控件的宽度
*/
private int mWidth;
/**
* 控件的高度
*/
private int mHeight;
public CustomImageView(Context context, AttributeSet attrs)
{
this(context, attrs, 0);
}
public CustomImageView(Context context)
{
this(context, null);
}
/**
* 初始化一些自定义的参数
*
* @param context
* @param attrs
* @param defStyle
*/
public CustomImageView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyle, 0);
int n = a.getIndexCount();
for (int i = 0; i < n; i++)
{
int attr = a.getIndex(i);
switch (attr)
{
case R.styleable.CustomImageView_src:
mSrc = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
break;
case R.styleable.CustomImageView_type:
type = a.getInt(attr, 0);// 默认为Circle
break;
case R.styleable.CustomImageView_borderRadius:
mRadius= a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10f,
getResources().getDisplayMetrics()));// 默认为10DP
break;
}
}
a.recycle();
}
2.构造中获取自定义属性：

/**
* TYPE_CIRCLE / TYPE_ROUND
*/
private int type;
private static final int TYPE_CIRCLE = 0;
private static final int TYPE_ROUND = 1;
/**
* 图片
*/
private Bitmap mSrc;
/**
* 圆角的大小
*/
private int mRadius;
/**
* 控件的宽度
*/
private int mWidth;
/**
* 控件的高度
*/
private int mHeight;
public CustomImageView(Context context, AttributeSet attrs)
{
this(context, attrs, 0);
}
public CustomImageView(Context context)
{
this(context, null);
}
/**
* 初始化一些自定义的参数
*
* @param context
* @param attrs
* @param defStyle
*/
public CustomImageView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyle, 0);
int n = a.getIndexCount();
for (int i = 0; i < n; i++)
{
int attr = a.getIndex(i);
switch (attr)
{
case R.styleable.CustomImageView_src:
mSrc = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
break;
case R.styleable.CustomImageView_type:
type = a.getInt(attr, 0);// 默认为Circle
break;
case R.styleable.CustomImageView_borderRadius:
mRadius= a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10f,
getResources().getDisplayMetrics()));// 默认为10DP
break;
}
}
a.recycle();
}

3、onMeasure中获取控件宽高：

/**
* 计算控件的高度和宽度
*/
@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)// match_parent , accurate
{
mWidth = specSize;
} else
{
// 由图片决定的宽
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)// match_parent , accurate
{
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);
}

4、根据Type绘制：

/**
* 绘制
*/
@Override
protected void onDraw(Canvas canvas)
{
switch (type)
{
// 如果是TYPE_CIRCLE绘制圆形
case TYPE_CIRCLE:
int min = Math.min(mWidth, mHeight);
/**
* 长度如果不一致，按小的值进行压缩
*/
mSrc = Bitmap.createScaledBitmap(mSrc, min, min, false);
canvas.drawBitmap(createCircleImage(mSrc, min), 0, 0, null);
break;
case TYPE_ROUND:
canvas.drawBitmap(createRoundConerImage(mSrc), 0, 0, null);
break;
}
}
/**
* 根据原图和变长绘制圆形图片
*
* @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, Config.ARGB_8888);
/**
* 产生一个同样大小的画布
*/
Canvas canvas = new Canvas(target);
/**
* 首先绘制圆形
*/
canvas.drawCircle(min / 2, min / 2, min / 2, paint);
/**
* 使用SRC_IN，参考上面的说明
*/
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
/**
* 绘制图片
*/
canvas.drawBitmap(source, 0, 0, paint);
return target;
}
/**
* 根据原图添加圆角
*
* @param source
* @return
*/
private Bitmap createRoundConerImage(Bitmap source)
{
final Paint paint = new Paint();
paint.setAntiAlias(true);
Bitmap target = Bitmap.createBitmap(mWidth, mHeight, Config.ARGB_8888);
Canvas canvas = new Canvas(target);
RectF rect = new RectF(0, 0, source.getWidth(), source.getHeight());
canvas.drawRoundRect(rect, mRadius, mRadius, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(source, 0, 0, paint);
return target;
}

本文转自 linuxpp 51CTO博客，原文链接：http://blog.51cto.com/1439337369/1834342，如需转载请自行联系原作者

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