安卓：如何用一个手指旋转视图 [英] Android: How to rotate a view with one finger

问题描述

我需要旋转它有一些按钮的视图。随着手指的移动，观点也应一同旋转与它相应的子视图。

I need to rotate a view which have some buttons. With the finger movement, view should also rotate along with it's child views accordingly.

到现在我已经实现了这一点：

Till now I have implemented this:

private RelativeLayout mCircle;
private double mCurrAngle = 0;
private double mPrevAngle = 0;
int i = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mCircle = (RelativeLayout) findViewById(R.id.circle);
    mCircle.setOnTouchListener(this); // Your activity should implement
                                        // OnTouchListener
}

@Override
public boolean onTouch(View v, MotionEvent event) {
    final float xc = mCircle.getWidth() / 2;
    final float yc = mCircle.getHeight() / 2;

    final float x = event.getX();
    final float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN: {
        mCircle.clearAnimation();
        mCurrAngle = Math.toDegrees(Math.atan2(x - xc, yc - y));
        break;
    }
    case MotionEvent.ACTION_MOVE: {
        mPrevAngle = mCurrAngle;
        mCurrAngle = Math.toDegrees(Math.atan2(x - xc, yc - y));
        mCircle.setRotation((float) (mPrevAngle - mCurrAngle));         

        animate(mPrevAngle, mCurrAngle, 0);
        break;
    }
    case MotionEvent.ACTION_UP: {
        mPrevAngle = mCurrAngle = 0;
        break;
    }
    }

    return true;
}

private void animate(double fromDegrees, double toDegrees,
        long durationMillis) {
    final RotateAnimation rotate = new RotateAnimation((float) fromDegrees,
            (float) toDegrees, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
            RotateAnimation.RELATIVE_TO_SELF, 0.5f);
    rotate.setDuration(durationMillis);
    rotate.setFillEnabled(true);
    rotate.setFillAfter(true);
    mCircle.startAnimation(rotate);
}

但不顺畅，因此，不能实施。

But it is not smooth and thus can't be implemented.

感谢。

推荐答案

首先，不要用动画，只要你想直接更改视图手指移动。

First, do not use animation, as you want to directly change the view as the finger moves.

然后，对于计算，它是一个更容易的OnTouchListener连接到要旋转视图的父视图，这样就不会被旋转本身进行修改。您的触摸事件的坐标

Then, for the computations, it is a lot easier to attach the OnTouchListener to a parent view of the view you want to rotate, so that the coordinate of your touch event is not modified by the rotation itself.

下面是code，如果你有ID的父视图@ + ID /根：

Here is the code if you have a parent view with id "@+id/root":

private RelativeLayout mRoot;
private RelativeLayout mCircle;
int i = 0;
float viewRotation;
double fingerRotation;
double newFingerRotation;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mRoot = (RelativeLayout)findViewById(R.id.root);
     mCircle = (RelativeLayout) findViewById(R.id.circle);
     mRoot.setOnTouchListener(this);
}

@Override
public boolean onTouch(View v, MotionEvent event) {

    final float x = event.getX();
    final float y = event.getY();

    final float xc = mRoot.getWidth()/2;
    final float yc = mRoot.getHeight()/2;

    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            viewRotation = mCircle.getRotation();
            fingerRotation = Math.toDegrees(Math.atan2(x - xc, yc - y));
            break;
        case MotionEvent.ACTION_MOVE:
            newFingerRotation = Math.toDegrees(Math.atan2(x - xc, yc - y));
            mCircle.setRotation((float)(viewRotation + newFingerRotation - fingerRotation));
            break;
        case MotionEvent.ACTION_UP:
            fingerRotation = newFingerRotation = 0.0f;
            break;
    }

    return true;
}

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