Android開發圓形ImageView實現

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1、自訂屬性，在value檔案夾下建立attrs檔案，聲明如下屬性

<declare-styleable name="CircleImageView">        <attr name="border_color" format="color"/>        <attr name="border_width" format="dimension"/></declare-styleable>

2、繼承ImageView ，重寫構造和ondraw方法

public class CircleImageView extends AppCompatImageView {    private int borderColor;    private int borderWidth;    private final static int DEFAULT_COLOR = Color.BLACK;    private final static int DEFAULT_BORDER_WIDTH = 0;    private Paint mPaint;    public CircleImageView(Context context) {        this(context,null);    }    public CircleImageView(Context context, @Nullable AttributeSet attrs) {        this(context, attrs,0);    }    public CircleImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.CircleImageView);        borderColor = typedArray.getColor(R.styleable.CircleImageView_border_color, DEFAULT_COLOR);        borderWidth = typedArray.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);        borderWidth = dp2px(context,borderWidth);        mPaint = new Paint();        typedArray.recycle();    }    public int dp2px(Context ctx,int dp) {        float scale = ctx.getResources().getDisplayMetrics().density;        return (int) (dp * scale + 0.5);    }    @Override    protected void onDraw(Canvas canvas) {        Drawable drawable = getDrawable();        if (drawable != null) {            Bitmap bitmap = ((BitmapDrawable)drawable).getBitmap();            Bitmap circleBitmap = getCircleBitmap(bitmap);            Rect srcRect = new Rect(0,0,circleBitmap.getWidth(),circleBitmap.getHeight());            Rect dstRect = new Rect(0,0,getWidth(),getHeight());            mPaint.reset();            canvas.drawBitmap(circleBitmap,srcRect,dstRect,mPaint);        }else {               super.onDraw(canvas);        }    }    private Bitmap getCircleBitmap(Bitmap bitmap) {        Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(),Bitmap.Config.ARGB_8888);        Canvas canvas = new Canvas(circleBitmap);        mPaint.setAntiAlias(true);        canvas.drawARGB(0,255,255,255);        mPaint.setColor(borderColor);        int radius = bitmap.getWidth() < bitmap.getHeight()? bitmap.getWidth():bitmap.getHeight();        canvas.drawCircle(radius/2,radius/2,radius/2-borderWidth,mPaint);        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));        Rect rect = new Rect(0,0,bitmap.getWidth(),bitmap.getHeight());        canvas.drawBitmap(bitmap,rect,rect,mPaint);        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OVER));        canvas.drawCircle(radius/2,radius/2,radius / 2,mPaint);        return circleBitmap;    }}

3、引入CircleImageView

<com.mydemo.view.CircleImageView        android:layout_width="100dp"        android:layout_height="100dp"        android:src="@drawable/logo"        app:border_color="#ffff00"        app:border_width="1dp"       />

　　

Android開發圓形ImageView實現