直播帶貨APP開發，圓形旋轉動畫

import android.animation.ObjectAnimator;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
 
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.support.annotation.Nullable;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;
import android.view.animation.LinearInterpolator;
 
/**
 * Created AY 2018-11-26 設定圓形ImageView以及旋轉動畫
 */
public class CircleImageView extends AppCompatImageView {
    private ObjectAnimator objectAnimator;
 
    public static final int STATE_PLAYING = 1;//正在播放
    public static final int STATE_PAUSE = 2;//暫停
    public static final int STATE_STOP = 3;//停止
    public int state;
 
    private float width;
    private float height;
    private float radius;
    private Paint paint;
    private Matrix matrix;
 
    public CircleImageView(Context context) {
        this(context, null);
    }
 
    public CircleImageView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }
 
    public CircleImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        paint = new Paint();
        paint.setAntiAlias(true);   //設定抗鋸齒
        matrix = new Matrix();      //初始化縮放矩陣
        init();
    }
 
    private void init() {
        state = STATE_STOP;
        objectAnimator = ObjectAnimator.ofFloat(this, "rotation", 0f, 359f);//添加旋轉動畫，旋轉中心預設為控件中點
        objectAnimator.setDuration(36000);//設定動畫時間
        objectAnimator.setInterpolator(new LinearInterpolator());//動畫時間線性漸變
        objectAnimator.setRepeatCount(ObjectAnimator.INFINITE);
        objectAnimator.setRepeatMode(ObjectAnimator.RESTART);
 
    }
 
    public void playAnim() {
        if (state == STATE_STOP) {
            objectAnimator.start();//動畫開始
            state = STATE_PLAYING;
        } else if (state == STATE_PAUSE) {
            objectAnimator.resume();//動畫重新開始
            state = STATE_PLAYING;
        }
    }
 
    public void pauseAnim(){
        if(state == STATE_PLAYING){
            objectAnimator.pause();//動畫暫停
            state = STATE_PAUSE;
        }
 
    }
 
    public void stopAnim() {
        objectAnimator.end();//動畫結束
        state = STATE_STOP;
    }
 
 
 
    /**
     * 測量控件的寬高，并擷取其内切圓的半徑
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width = getMeasuredWidth();
        height = getMeasuredHeight();
        radius = Math.min(width, height) / 2;
    }
 
    @Override
    protected void onDraw(Canvas canvas) {
        paint.setShader(initBitmapShader());//将着色器設定給畫筆
        canvas.drawCircle(width / 2, height / 2, radius, paint);//使用畫筆在畫布上畫圓
    }
 
    /**
     * 擷取ImageView中資源圖檔的Bitmap，利用Bitmap初始化圖檔着色器,通過縮放矩陣将原資源圖檔縮放到鋪滿整個繪制區域，避免邊界填充
     */
    private BitmapShader initBitmapShader() {
        Bitmap bitmap = ((BitmapDrawable) getDrawable()).getBitmap();
        BitmapShader bitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        float scale = Math.max(width / bitmap.getWidth(), height / bitmap.getHeight());
        matrix.setScale(scale, scale);//将圖檔寬高等比例縮放，避免拉伸
        bitmapShader.setLocalMatrix(matrix);
        return bitmapShader;
    }
 
}           

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