MainActivity.java

package com.msh_n.myp.customview1;

public class MainActivity extends AppCompatActivity {

    Button button;
   
    float newAngle;
    float oldAngle;
    ObjectAnimator animatorX;
    ValueAnimator.AnimatorUpdateListener mListener;

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

        button = (Button) findViewById(R.id.button1);
        pieView = (PieView) findViewById(R.id.pieView2);

        animatorX = ObjectAnimator.ofFloat(pieView, "angle", 0, 180);
        animatorX.setDuration(4000);

        mListener = new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                pieView.invalidate();
            }
        };

        animatorX.addUpdateListener(mListener);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                animatorX.start();
            }
        });
    }    

}