原文链接 https://jungletian.github.io/2015/09/17/350%E8%A1%8C%E4%BB%A3%E7%A0%81%E5%AE%9E%E7%8E%B0%E5%9C%86%E5%BD%A2View/
注：以下为加速网络访问所做的原文缓存，经过重新格式化，可能存在格式方面的问题，或偶有遗漏信息，请以原文为准。
上一篇介绍了150行代码实现滑动退出功能，相对来说比较简单，那么这篇文章稍微复杂点，有350行代码。
- CircleImageView：继承系统的View，重写系统的方法；
- 自定义style属性：供使用者在xml文件中配置，方便使用； 有多么好用就不罗嗦了（我左侧的头像就是），直接上代码： <!--more-->
public class CircleImageView extends ImageView {
private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;
private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
private static final int COLORDRAWABLE_DIMENSION = 2;
private static final int DEFAULT_BORDER_WIDTH = 0;
private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
private static final boolean DEFAULT_BORDER_OVERLAY = false;
private final RectF mDrawableRect = new RectF();
private final RectF mBorderRect = new RectF();
private final Matrix mShaderMatrix = new Matrix();
private final Paint mBitmapPaint = new Paint();
private final Paint mBorderPaint = new Paint();
private int mBorderColor = DEFAULT_BORDER_COLOR;
private int mBorderWidth = DEFAULT_BORDER_WIDTH;
private Bitmap mBitmap;
private BitmapShader mBitmapShader;
private int mBitmapWidth;
private int mBitmapHeight;
private float mDrawableRadius;
private float mBorderRadius;
private ColorFilter mColorFilter;
private boolean mReady;
private boolean mSetupPending;
private boolean mBorderOverlay;
public CircleImageView(Context context) {
super(context);
init();
}
public CircleImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);
mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR);
mBorderOverlay = a.getBoolean(R.styleable.CircleImageView_border_overlay, DEFAULT_BORDER_OVERLAY);
a.recycle();
init();
}
private void init() {
super.setScaleType(SCALE_TYPE);
mReady = true;
if (mSetupPending) {
setup();
mSetupPending = false;
}
}
@Override
public ScaleType getScaleType() {
return SCALE_TYPE;
}
@Override
public void setScaleType(ScaleType scaleType) {
if (scaleType != SCALE_TYPE) {
throw new IllegalArgumentException(String.format("ScaleType %s not supported.", scaleType));
}
}
@Override
public void setAdjustViewBounds(boolean adjustViewBounds) {
if (adjustViewBounds) {
throw new IllegalArgumentException("adjustViewBounds not supported.");
}
}
@Override
protected void onDraw(Canvas canvas) {
if (getDrawable() == null) {
return;
}
canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint);
if (mBorderWidth != 0) {
canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius, mBorderPaint);
}
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
setup();
}
public int getBorderColor() {
return mBorderColor;
}
public void setBorderColor(int borderColor) {
if (borderColor == mBorderColor) {
return;
}
mBorderColor = borderColor;
mBorderPaint.setColor(mBorderColor);
invalidate();
}
public void setBorderColorResource(@ColorRes int borderColorRes) {
setBorderColor(getContext().getResources().getColor(borderColorRes));
}
public int getBorderWidth() {
return mBorderWidth;
}
public void setBorderWidth(int borderWidth) {
if (borderWidth == mBorderWidth) {
return;
}
mBorderWidth = borderWidth;
setup();
}
public boolean isBorderOverlay() {
return mBorderOverlay;
}
public void setBorderOverlay(boolean borderOverlay) {
if (borderOverlay == mBorderOverlay) {
return;
}
mBorderOverlay = borderOverlay;
setup();
}
@Override
public void setImageBitmap(Bitmap bm) {
super.setImageBitmap(bm);
mBitmap = bm;
setup();
}
@Override
public void setImageDrawable(Drawable drawable) {
super.setImageDrawable(drawable);
mBitmap = getBitmapFromDrawable(drawable);
setup();
}
@Override
public void setImageResource(@DrawableRes int resId) {
super.setImageResource(resId);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}
@Override
public void setImageURI(Uri uri) {
super.setImageURI(uri);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}
@Override
public void setColorFilter(ColorFilter cf) {
if (cf == mColorFilter) {
return;
}
mColorFilter = cf;
mBitmapPaint.setColorFilter(mColorFilter);
invalidate();
}
private Bitmap getBitmapFromDrawable(Drawable drawable) {
if (drawable == null) {
return null;
}
if (drawable instanceof BitmapDrawable) {
return ((BitmapDrawable) drawable).getBitmap();
}
try {
Bitmap bitmap;
if (drawable instanceof ColorDrawable) {
bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION, COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
} else {
bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), BITMAP_CONFIG);
}
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
} catch (OutOfMemoryError e) {
return null;
}
}
private void setup() {
if (!mReady) {
mSetupPending = true;
return;
}
if (mBitmap == null) {
return;
}
mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
mBitmapPaint.setAntiAlias(true);
mBitmapPaint.setShader(mBitmapShader);
mBorderPaint.setStyle(Paint.Style.STROKE);
mBorderPaint.setAntiAlias(true);
mBorderPaint.setColor(mBorderColor);
mBorderPaint.setStrokeWidth(mBorderWidth);
mBitmapHeight = mBitmap.getHeight();
mBitmapWidth = mBitmap.getWidth();
mBorderRect.set(0, 0, getWidth(), getHeight());
mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2);
mDrawableRect.set(mBorderRect);
if (!mBorderOverlay) {
mDrawableRect.inset(mBorderWidth, mBorderWidth);
}
mDrawableRadius = Math.min(mDrawableRect.height() / 2, mDrawableRect.width() / 2);
updateShaderMatrix();
invalidate();
}
private void updateShaderMatrix() {
float scale;
float dx = 0;
float dy = 0;
mShaderMatrix.set(null);
if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {
scale = mDrawableRect.height() / (float) mBitmapHeight;
dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
} else {
scale = mDrawableRect.width() / (float) mBitmapWidth;
dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
}
mShaderMatrix.setScale(scale, scale);
mShaderMatrix.postTranslate((int) (dx + 0.5f) + mDrawableRect.left, (int) (dy + 0.5f) + mDrawableRect.top);
mBitmapShader.setLocalMatrix(mShaderMatrix);
}
}
<resources>
<declare-styleable name="CircleImageView">
<attr name="border_width" format="dimension" />
<attr name="border_color" format="color" />
<attr name="border_overlay" format="boolean" />
</declare-styleable>
</resources>