Android之自定义View：圆形ImageView实现可暂停的旋转动画效果

最近，虽然公司的安卓开发相对还是挺多，依旧在学习自定义View。不怕实现的简单，慢慢做、慢慢理解。

效果图：

1.先实现自定义圆形ImageView：

需要了解上一篇：Android之Canvas绘图中PorterDuffXfermode

首先获取到图片的Bitmap，然后进行裁剪圆形的bitmap，然后在onDraw（）进行绘制圆形图片输出。

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;

/**
 * Created by zachary on 2019/04/08.
 * 圆形ImageView
 */
public class MusicView extends AppCompatImageView {

    private Paint paint;

    public MusicView(Context context) {
        this(context,null);
    }

    public MusicView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public MusicView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        paint = new Paint();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //获取图像资源
        Drawable drawable = getDrawable();
        if (null != drawable) {
            Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
            Bitmap b = getCircleBitmap(bitmap);
            //上层
            final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
            //下层
            final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
            paint.reset();
            canvas.drawBitmap(b, rectSrc, rectDest, paint);
        } else {
            super.onDraw(canvas);
        }
    }

    /**
     * 获取圆形图片方法
     * @param bitmap
     * @return Bitmap
     */
    private Bitmap getCircleBitmap(Bitmap bitmap) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        final int color = 0xffffffff;

        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        //设置抗锯齿
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        int x = bitmap.getWidth();
        //圆形的大小
        canvas.drawCircle(x / 2, x / 2, x / 2, paint);
        //PorterDuff.Mode.SRC_IN模式组合效果
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }
}

2.实现可暂停的旋转效果

因为补间动画（RotateAnimation）只有开始和结束的方法，实现暂停与开始需要记录旋转的角度，而使用属性动画（ObjectAnimator）则可以使用已经封装好的方法，比较适合我们的需求。

import android.animation.ObjectAnimator;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;
import android.view.animation.LinearInterpolator;

/**
 * Created by zachary on 2019/04/08.
 * 圆形ImageView，旋转操作（属性动画ObjectAnimator）
 */
public class MusicView extends AppCompatImageView {

    private ObjectAnimator objectAnimator;

    public static final int STATE_PLAYING = 1;     //正在播放
    public static final int STATE_PAUSE = 2;       //暂停
    public static final int STATE_STOP = 3;        //停止
    public int state;

    private Paint paint;

    public MusicView(Context context) {
        this(context,null);
    }

    public MusicView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public MusicView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        paint = new Paint();
        init();
    }

    private void init(){
        state = STATE_STOP;
        //添加旋转动画，旋转中心默认为控件中点
        objectAnimator = ObjectAnimator.ofFloat(this, "rotation", 0f, 360f);
        //设置动画时间：3s
        objectAnimator.setDuration(3000);
        //动画：时间线性渐变
        objectAnimator.setInterpolator(new LinearInterpolator());
        objectAnimator.setRepeatCount(ObjectAnimator.INFINITE);
        objectAnimator.setRepeatMode(ObjectAnimator.RESTART);
    }

    /**
     * 绘制圆形图片
     */
    @Override
    protected void onDraw(Canvas canvas) {
        Drawable drawable = getDrawable();
        if (null != drawable) {
            Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
            Bitmap b = getCircleBitmap(bitmap);
            //上层
            final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
            //下层
            final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
            paint.reset();
            canvas.drawBitmap(b, rectSrc, rectDest, paint);
        } else {
            super.onDraw(canvas);
        }
    }

    /**
     * 获取圆形图片方法
     * @param bitmap
     * @return Bitmap
     */
    private Bitmap getCircleBitmap(Bitmap bitmap) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        final int color = 0xff424242;

        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        int x = bitmap.getWidth();

        canvas.drawCircle(x / 2, x / 2, x / 2, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    public void playMusic(){
        if(state == STATE_STOP){
            objectAnimator.start();    //动画开始
            state = STATE_PLAYING;
        }else if(state == STATE_PAUSE){
            objectAnimator.resume();   //动画重新开始
            state = STATE_PLAYING;
        }else if(state == STATE_PLAYING){
            objectAnimator.pause();    //动画暂停
            state = STATE_PAUSE;
        }
    }

    public void stopMusic(){
        objectAnimator.end();         //动画结束
        state = STATE_STOP;
    }
}