imageview 四角触摸放大旋转可拖拽 不能超出屏幕

你可以使用Android提供的`Matrix`类实现对`ImageView`的缩放、旋转和拖拽操作。以下是实现的大致步骤：

1. 继承`ImageView`，重写`onDraw()`方法，在此方法中使用`Matrix`类来实现对图片的变换。
2. 在`onTouchEvent()`方法中处理触摸事件，分别对应不同的操作（缩放、旋转、拖拽）。
3. 实现边界检测，确保图片不会超出屏幕。

下面是一个简单的示例代码，可以实现对`ImageView`的缩放、旋转和拖拽操作，并且确保图片不会超出屏幕。

public class TouchImageView extends ImageView {
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private static final int ROTATE = 3;

    private int mode = NONE;

    private PointF last = new PointF();
    private PointF mid = new PointF();
    private float oldDist = 1f;
    private float oldRotation = 0;

    private boolean canDrag = false;
    private RectF bounds = new RectF();

    public TouchImageView(Context context) {
        super(context);
        init();
    }

    public TouchImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public TouchImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        setScaleType(ScaleType.MATRIX);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                last.set(event.getX(), event.getY());
                mode = DRAG;
                canDrag = true;
                break;

            case MotionEvent.ACTION_POINTER_DOWN:
                oldDist = spacing(event);
                oldRotation = rotation(event);
                midPoint(mid, event);
                mode = ZOOM;
                break;

            case MotionEvent.ACTION_MOVE:
                if (mode == DRAG) {
                    float dx = event.getX() - last.x;
                    float dy = event.getY() - last.y;
                    if (canDrag) {
                        Matrix matrix = getImageMatrix();
                        matrix.postTranslate(dx, dy);
                        setImageMatrix(matrix);
                    }
                    last.set(event.getX(), event.getY());
                } else if (mode == ZOOM && event.getPointerCount() == 2) {
                    float newDist = spacing(event);
                    float newRotation = rotation(event);
                    float scale = newDist / oldDist;
                    Matrix matrix = getImageMatrix();
                    matrix.postScale(scale, scale, mid.x, mid.y);
                    matrix.postRotate(newRotation - oldRotation, mid.x, mid.y);
                    setImageMatrix(matrix);
                    oldDist = newDist;
                    oldRotation = newRotation;
                }
                break;

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                canDrag = false;
                break;
        }

        // 边界检测
        Matrix matrix = getImageMatrix();
        matrix.mapRect(bounds, new RectF(0, 0, getWidth(), getHeight()));
        float dx = 0, dy = 0;
        if (bounds.left > 0) {
            dx = -bounds.left;
        } else if (bounds.right < getWidth()) {
            dx = getWidth() - bounds.right;
        }
        if (bounds.top > 0) {
            dy = -bounds.top;
        } else if (bounds.bottom < getHeight()) {
            dy = getHeight() - bounds.bottom;
        }
        if (dx != 0 || dy != 0) {
            matrix.postTranslate(dx, dy);
            setImageMatrix(matrix);
        }

        return true;
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }
}

在使用时，只需要将`ImageView`替换为`TouchImageView`，即可实现对图片的缩放、旋转和拖拽操作，并且确保图片不会超出屏幕。