Android 中基于一个手柄旋转和缩放视图

我正在尝试根据 Android 中的一个“拖动”手柄来旋转和缩放视图。随着布局旋转和视图大小调整，最终结果应该是拖动手柄跟随用户手指移动。

这是基于结合这两个问题：

1. 如何使用手柄在android中缩放视图？
2. 在android中绕两点旋转不起作用

唯一看起来错误的是轮换代码。

这是我的活动代码：

public class MainActivity extends Activity {
    ImageView imageView;
    ImageView dragHandle;
    RelativeLayout layout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.imageView1);
        imageView.setBackgroundColor(Color.MAGENTA);
        dragHandle = (ImageView) findViewById(R.id.imageView2);
        dragHandle.setBackgroundColor(Color.CYAN);
        layout = (RelativeLayout) findViewById(R.id.relativeLayout2);
        layout.setBackgroundColor(Color.YELLOW);
        setUpResize();

    }

    public void setUpResize() {
        dragHandle.setOnTouchListener(new View.OnTouchListener() {

            float centerX, centerY, startR, startScale, startX, startY;

            float startAngle;
            float zeroAngle;
            int firstPointX;
            int firstPointY;

            public boolean onTouch(View v, MotionEvent e) {

                if (e.getAction() == MotionEvent.ACTION_DOWN) {

                    // calculate center of image
                    centerX = (imageView.getLeft() + imageView.getRight()) / 2f;
                    centerY = (imageView.getTop() + imageView.getBottom()) / 2f;

                    // recalculate coordinates of starting point
                    startX = e.getRawX() - dragHandle.getX() + centerX;
                    startY = e.getRawY() - dragHandle.getY() + centerY;

                    // get starting distance and scale
                    startR = (float) Math.hypot(e.getRawX() - startX, e.getRawY() - startY);
                    startScale = imageView.getScaleX();

                    /*
                     * Rotate code
                     */

                    int[] locationOfLayout = new int[2];
                    int[] locationOfDrag = new int[2];

                    layout.getLocationOnScreen(locationOfLayout);
                    dragHandle.getLocationOnScreen(locationOfDrag);

                    firstPointX = locationOfLayout[0];
                    firstPointY = locationOfLayout[1];

                    float secondPointX = e.getRawX();
                    float secondPointY = e.getRawY();

                    zeroAngle = findRotation(firstPointX, firstPointY, secondPointX, secondPointY); // remember
                                                                                                    // "zero"
                                                                                                    // angle
                    startAngle = layout.getRotation(); // remember angle at
                                                        // which layout is
                                                        // rotated at the start

                } else if (e.getAction() == MotionEvent.ACTION_MOVE) {

                    // calculate new distance
                    float newR = (float) Math.hypot(e.getRawX() - startX, e.getRawY() - startY);

                    // set new scale
                    float newScale = newR / startR * startScale;
                    imageView.setScaleX(newScale);
                    imageView.setScaleY(newScale);

                    // move handler image
                    dragHandle.setX(centerX + imageView.getWidth() / 2f * newScale);
                    dragHandle.setY(centerY + imageView.getHeight() / 2f * newScale);

                    /*
                     * Rotate code
                     */

                    layout.setRotation(findRotation(firstPointX, firstPointY, e.getRawX(), e.getRawY()) - zeroAngle
                            + startAngle); // rotate relative to start and zero
                                            // angle

                } else if (e.getAction() == MotionEvent.ACTION_UP) {

                }
                return true;
            }
        });
    }

    private float findRotation(float firstPointX, float firstPointY, float secondPointX, float secondPointY) {
        double delta_x = (secondPointX - firstPointX);
        double delta_y = (secondPointY - firstPointY);
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }
}

xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <RelativeLayout
        android:id="@+id/relativeLayout2"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerInParent="true" >

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_centerVertical="true"
            android:src="@drawable/ic_launcher" />

        <ImageView
            android:id="@+id/imageView2"
            android:layout_width="20dp"
            android:layout_height="20dp"
            android:layout_below="@+id/imageView1"
            android:layout_toRightOf="@+id/imageView1"
            android:src="@drawable/meanicons" />

    </RelativeLayout>

</RelativeLayout>

如果您需要使用一个处理程序图标同时调整图像大小和旋转图像，则应执行一些三角计算。

根据图像的初始角度和连接图像中心与当前手指位置的矢量旋转的角度，计算图像应旋转的角度并不困难。稍微复杂一点的任务是将处理程序放置在屏幕的适当位置，使其始终连接主图像的一角。

public void setUpResize() {
    dragHandle.setOnTouchListener(new View.OnTouchListener() {

        float centerX, centerY, startR, startScale, startX, startY, startRotation, startA ;

        public boolean onTouch(View v, MotionEvent e) {

            if (e.getAction() == MotionEvent.ACTION_DOWN) {

                centerX = (imageView.getLeft() + imageView.getRight()) / 2f;
                centerY = (imageView.getTop() + imageView.getBottom()) / 2f;

                startX = e.getRawX() - dragHandle.getX() + centerX;
                startY = e.getRawY() - dragHandle.getY() + centerY; 

                startR = (float) Math.hypot(e.getRawX() - startX, e.getRawY() - startY);
                startA = (float) Math.toDegrees(Math.atan2(e.getRawY() - startY, e.getRawX() - startX));

                startScale = imageView.getScaleX();
                startRotation = imageView.getRotation();

            } else if (e.getAction() == MotionEvent.ACTION_MOVE) {

                float newR = (float) Math.hypot(e.getRawX() - startX, e.getRawY() - startY);
                float newA = (float) Math.toDegrees(Math.atan2(e.getRawY() - startY, e.getRawX() - startX));
                float newScale = newR / startR * startScale;
                float newRotation = newA - startA + startRotation;

                imageView.setScaleX(newScale);
                imageView.setScaleY(newScale);
                imageView.setRotation(newRotation);


                // ----- this part takes some effort to understand... ------
                dragHandle.setX((float) (centerX + Math.hypot(imageView.getWidth(), imageView.getHeight())/2f * newScale 
                        * Math.cos(Math.toRadians(newRotation) + Math.atan2(imageView.getHeight(), imageView.getWidth()))));

                dragHandle.setY((float) (centerY + Math.hypot(imageView.getWidth(), imageView.getHeight())/2f * newScale 
                        * Math.sin(Math.toRadians(newRotation) + Math.atan2(imageView.getHeight(), imageView.getWidth()))));
                //-----------------------------------------------------------

                dragHandle.setPivotX(0);
                dragHandle.setPivotY(0);
                dragHandle.setRotation(newRotation);


            } else if (e.getAction() == MotionEvent.ACTION_UP) {

            }
            return true;
        }
    });
}

那么，我在做什么？

Math.hypot(imageView.getWidth(), imageView.getHeight()) / 2f * newScale

--这计算主图像对角线的一半长度，i。 e.其中心与角点之间的距离

Math.atan2(imageView.getHeight(), imageView.getWidth())

--这是对角线最初旋转的角度（因为图像不能是正方形，所以这个角度并不总是 45 度）

Math.cos(Math.toRadians(newRotation) + Math.atan2(imageView.getHeight(), imageView.getWidth()))

--这为我们提供了单位向量 X 轴上的投影，旋转了一个由图像旋转角度及其对角线初始旋转角度组成的角度。乘以对角线长度的一半后，我们得到图像角点的X。

与 Y 相同，但使用sin代替cos.