PTZView

效果图以及相关的两张图片资源：

实现步骤：

1. 继承View
2. 重写onTouchEvent，根据触摸坐标计算角度
3. 重写onDraw，根据角度旋转并绘制图片

代码如下：

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import androidx.annotation.IntDef;

/**
 * 自定义云台控件
 * <p>2020-06-02: create by zenghm
 */
public class PTZView extends View {

    public static final int NONE = 0;
    public static final int TOP = 1;
    public static final int BOTTOM = 2;
    public static final int LEFT = 3;
    public static final int RIGHT = 4;

    @IntDef({NONE, LEFT, TOP, RIGHT, BOTTOM})
    public @interface Direction {
    }

    public interface DirectionChangedListener {
        /**
         * 方向变化回调
         *
         * @param oldDirection 之前的方向
         * @param curDirection 当前的方向
         */
        void onDirectionChanged(PTZView view, @Direction int oldDirection, @Direction int curDirection);
    }

    private DirectionChangedListener mListener;
    @Direction
    private int mDirection = NONE;
    private float mCenterX, mCenterY;
    private float mAngel = 0;

    private Bitmap mDefaultBitmap;
    private Bitmap mPressBitmap;
    private Matrix mMatrix = new Matrix();
    private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

    public PTZView(Context context) {
        this(context, null, 0);
    }

    public PTZView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public PTZView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // 加载资源
        Resources res = context.getResources();
        mDefaultBitmap = BitmapFactory.decodeResource(res, R.drawable.ptz_default);
        mPressBitmap = BitmapFactory.decodeResource(res, R.drawable.ptz_press);
    }

    public void setOnDirectionChangedListener(DirectionChangedListener listener) {
        mListener = listener;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mCenterX = (float) w / 2;
        mCenterY = (float) h / 2;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Bitmap bitmap = isPressed() ? mPressBitmap : mDefaultBitmap;
        // 计算图片缩放
        float sx = (float) getWidth() / bitmap.getWidth();
        float sy = (float) getHeight() / bitmap.getHeight();
        // 设置变换矩阵（缩放、旋转）
        mMatrix.reset();
        mMatrix.postScale(sx, sy);
        mMatrix.postRotate(-mAngel, mCenterX, mCenterY);
        // 绘制图片
        canvas.drawBitmap(bitmap, mMatrix, mPaint);
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //super.onTouchEvent(event);
        if (!isEnabled())
            return false;

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                setPressed(true);
                postInvalidate();
                break;

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                if (mListener != null) {
                    mListener.onDirectionChanged(this, mDirection, NONE);
                }
                mDirection = NONE;
                mAngel = 0;
                setPressed(false);
                postInvalidate();
                break;

            case MotionEvent.ACTION_MOVE:
                // 计算角度
                float x = event.getX() - mCenterX;
                float y = mCenterY - event.getY();
                mAngel = (float) (Math.atan2(y, x) / Math.PI * 180);
                // 重新绘制
                postInvalidate();
                // 根据角度判断方向
                int direction;
                if (mAngel > -45 && mAngel <= 45) {
                    direction = LEFT;
                } else if (mAngel > 45 && mAngel <= 135) {
                    direction = TOP;
                } else if (mAngel <= -45 && mAngel > -135) {
                    direction = BOTTOM;
                } else {
                    direction = RIGHT;
                }
                // 回调方向变化
                if (mListener != null && mDirection != direction) {
                    mListener.onDirectionChanged(this, mDirection, direction);
                }
                mDirection = direction;
                break;

            default:
                break;
        }
        return true;
    }
}

 【注】可以通过自定义属性传入图片，增强控件的自定义能力。自定义属性不在本文的讨论范围。

谢谢阅读，如有谬误，多谢指正。