试图在android中旋转布局，画布似乎不会旋转

Question

我已经学习了教程here（它在触摸/拖动时动态旋转图像）并试图用整个布局而不是仅仅一个图像重构它，所以我从TutorialActivity改变了rotateDialer（）方法，如下所示：

private void rotateDialer(float degrees) {
    //matrix.postRotate(degrees, dialerWidth / 2, dialerHeight / 2);
    //dialer.setImageMatrix(matrix);
    dialer.setNextRotation(degrees, dialerWidth / 2, dialerHeight  / 2);
    dialer.invalidate();
    info.setText("Current Quadrant Touched = "+currentQuadrantTouched
            +"
Angle = "+degrees);
}

其中dialer是一个自定义布局我用一个重写的onDraw（）方法创建，该方法旋转画布但在setNextRotation（）方法中设置了多个度数，但画布似乎没有旋转！这是我的自定义布局：

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.RelativeLayout;

public class DialView extends FrameLayout {
public static final String LOG_TAG = "DialView";
RelativeLayout dialView;
float degrees;
float px;
float py;

public DialView(Context context) {
    super(context);
    init();
    // TODO Auto-generated constructor stub
}

public DialView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
    // TODO Auto-generated constructor stub
}
public DialView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
    init();
}


private void init()
{
    //initialise rotation
    this.degrees = 0;
    this.px = 0;
    this.py = 0;
    LayoutInflater inflator = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    dialView = (RelativeLayout) inflator.inflate(R.layout.dial_view, this,false);
    addView(dialView);
    Log.d(LOG_TAG, "DialView: init() "+ degrees+"degrees around ("+getWidth() / 2+","+getHeight() / 2+")");

}



public void setNextRotation(float degrees, float px, float py)
{
    this.degrees = degrees;
    this.px = px;
    this.py = py;
    Log.d(LOG_TAG, "Next Rotation = "+ degrees+"degrees around ("+px+","+py+")");
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.save();
    // canvas.rotate(45,<appropriate x pivot value>,<appropriate y pivot value>);
     canvas.rotate(degrees, px, py);
     Log.d(LOG_TAG, "onDraw: Rotation = "+ degrees+"degrees around ("+px+","+py+")");
     super.onDraw(canvas);
     canvas.restore();

}


}

这是dial_view.xml：

<ImageView
    android:id="@+id/topLeftImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginLeft="38dp"
    android:clickable="true"
    android:layout_marginTop="28dp"
    android:src="@drawable/icon" />

<ImageView
    android:id="@+id/topRightImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:clickable="true"
    android:layout_alignParentRight="true"
    android:layout_marginRight="50dp"
    android:src="@drawable/icon" />

<ImageView
    android:id="@+id/bottomLeftImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:clickable="true"
    android:layout_marginBottom="24dp"
    android:layout_marginLeft="22dp"
    android:src="@drawable/icon" />

<ImageView
    android:id="@+id/bottomRightImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:clickable="true"
    android:layout_alignParentRight="true"
    android:layout_marginRight="28dp"
    android:src="@drawable/icon" />

</RelativeLayout>

为什么画布不会明显旋转？在计算度数后，我在onTouch（）中使拨号器无效，并且计算工作正常（我正在更改日志中的值）但视图似乎没有旋转，我在做什么错误？