android中RoundImageView如何实现鼠标进入时和退出时显示不同效果

Android 中的 RoundImageView 是一个自定义 View，可以根据需求自己实现鼠标进入时和退出时显示不同效果的功能。

以下是一个实现鼠标进入时和退出时显示不同效果的 RoundImageView 的示例代码：

public class RoundImageView extends ImageView {

    private int mBorderColor = Color.RED;
    private int mBorderWidth = 0;
    private int mRadius = 0;

    public RoundImageView(Context context) {
        super(context);
    }

    public RoundImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initAttrs(context, attrs);
    }

    public RoundImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initAttrs(context, attrs);
    }

    private void initAttrs(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RoundImageView);
        mBorderColor = a.getColor(R.styleable.RoundImageView_borderColor, Color.RED);
        mBorderWidth = a.getDimensionPixelSize(R.styleable.RoundImageView_borderWidth, 0);
        mRadius = a.getDimensionPixelSize(R.styleable.RoundImageView_radius, 0);
        a.recycle();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        Drawable drawable = getDrawable();
        if (drawable == null) {
            return;
        }
        if (getWidth() == 0 || getHeight() == 0) {
            return;
        }
        Bitmap b = ((BitmapDrawable) drawable).getBitmap();
        if (b == null) {
            return;
        }
        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
        int w = getWidth(), h = getHeight();
        Bitmap roundBitmap = getCroppedBitmap(bitmap, w, h);
        canvas.drawBitmap(roundBitmap, 0, 0, null);
        if (mBorderWidth > 0) {
            Paint paint = new Paint();
            paint.setColor(mBorderColor);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(mBorderWidth);
            canvas.drawCircle(w / 2, h / 2, mRadius - mBorderWidth / 2, paint);
        }
    }

    private Bitmap getCroppedBitmap(Bitmap bmp, int radius, int border) {
        Bitmap sbmp;
        if (bmp.getWidth() != radius || bmp.getHeight() != radius) {
            float smallest = Math.min(bmp.getWidth(), bmp.getHeight());
            float factor = smallest / radius;
            sbmp = Bitmap.createScaledBitmap(bmp, (int) (bmp.getWidth() / factor), (int) (bmp.getHeight() / factor), false);
        } else {
            sbmp = bmp;
        }
        Bitmap output = Bitmap.createBitmap(radius, radius, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        int color = Color.WHITE;
        Paint paint = new Paint();
        Rect rect = new Rect(0, 0, radius, radius);
        paint.setAntiAlias(true);
        paint.setColor(color);
        canvas.drawARGB(0, 0, 0, 0);
        canvas.drawCircle(radius / 2, radius / 2, mRadius, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(sbmp, rect, rect, paint);
        return output;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // 鼠标进入时的处理
                mBorderColor = Color.BLUE;
                mBorderWidth = 10;
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                // 鼠标退出时的处理
                mBorderColor = Color.RED;
                mBorderWidth = 0;
                invalidate();
                break;
            default:
                break;
        }
        return super.onTouchEvent(event);
    }
}

在 RoundImageView 中，我们重写了 onTouchEvent 方法，当鼠标进入时修改了边框的颜色和宽度，在鼠标退出时则恢复为原来的颜色和宽度。这样就实现了鼠标进入时和退出时显示不同效果的功能。