import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.os.Build;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.View;

import com.example.admin.listviewdemo.R;

public class newCircle extends View {

    private Bitmap mSourceBitmap;

    PorterDuffXfermode xfermode;
    private Paint paint;

    public newCircle(Context context) {
        this(context, null);
        init();
    }

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

    public newCircle(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {

        paint=new Paint();
        paint.setAntiAlias(true);//設(shè)置抗鋸齒
        paint.setStyle(Paint.Style.FILL);//設(shè)置填充樣式
        paint.setDither(true);//設(shè)定是否使用圖像抖動(dòng)處理，會(huì)使繪制出來(lái)的圖片顏色更加平滑和飽滿樊展，圖像更加清晰
        paint.setFilterBitmap(true);//加快顯示速度蓝厌，本設(shè)置項(xiàng)依賴于dither和xfermode的設(shè)置
        xfermode=new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);//繪制交集脖旱，顯示上層
    }

    @Override
    protected void onDraw(Canvas canvas) {

        // 生成圓形Bitmap過(guò)程
        mSourceBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.yyy);//從資源文件中解析獲取Bitmap
        /**
         * 設(shè)置View的離屏緩沖蛹锰。在繪圖的時(shí)候新建一個(gè)“層”泥兰，所有的操作都在該層而不會(huì)影響該層以外的圖像
         * 必須設(shè)置叉趣，否則設(shè)置的PorterDuffXfermode會(huì)無(wú)效
         */
        int sc=canvas.saveLayer(0,0,getWidth()*2,getHeight()*2,paint,Canvas.ALL_SAVE_FLAG);

        Matrix matrix = new Matrix();
        float xscal = getWidth()/(1.0f*mSourceBitmap.getWidth());
        float yscal = getHeight()/(1.0f*mSourceBitmap.getHeight());
        float scal = xscal<yscal?yscal:xscal;
        matrix.setScale(scal, scal);

        canvas.drawCircle(getWidth()/2,getHeight()/2,getWidth(),paint);
        paint.setXfermode(xfermode);
        canvas.translate(-(mSourceBitmap.getWidth()*scal - getWidth())/2,-(mSourceBitmap.getHeight()*scal - getHeight())/2);
        canvas.drawBitmap(mSourceBitmap,matrix,paint);
        paint.setXfermode(null);
        /**
         * 還原畫(huà)布貌虾，與canvas.saveLayer配套使用
         */
        canvas.restoreToCount(sc);
    }
}