android开发笔记之多媒体—Canvas的相关方法

末蓝、 2022-07-24 05:27 210阅读 0赞

——Canvas相关方法

——画线：canvas.drawLine(20, 20, 200, 200, paint)
    
       ——画矩形：canvas.drawRect(20, 20, 200, 200, paint)
    
       ——画圆：canvas.drawCircle(250, 250, 250, paint);
    
       ——画扇形：canvas.drawArc(rectF, 0, 90, true, paint)
    
       ——画三角形：Path path = new Path();
                   path.moveTo(250, 0);
                path.lineTo(150, 300);
                   path.arcTo(new RectF(150, 200, 350, 400), 0, 180);
                    path.lineTo(350, 300);
                path.lineTo(250, 0);
                   path.close();
                   canvas.drawPath(path, paint);

效果图：

![这里写图片描述][20160514204626031]

核心代码：

public class MainActivity extends Activity { 
    
        private ImageView iv;
        private Bitmap bitmap;//画纸
        private Canvas canvas;//画布
        private Paint paint;//画笔
        private float radius = 60;
        private final static float DEGREE = 36; //五角星角度 
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            iv = (ImageView) findViewById(R.id.iv);
        }
        //画一条线
        public void drawLine(View view){
            init();
            //第一二参数表示直线的起始点坐标
            //第三四参数表示直线的终点坐标
            canvas.drawLine(20, 20, 200, 200, paint);
            iv.setImageBitmap(bitmap);
        }
        //画一个矩形
        public void drawRect(View view) {
            init();
            //第一个参数表示矩形左边距离画布左边的距离
            //第二个参数表示矩形上边距离画布上边的距离
            //第三个参数表示矩形右边距离画布左边的距离
            //第四个参数表示矩形下边距离画布上边的距离
            canvas.drawRect(20, 20, 300, 200, paint);
            iv.setImageBitmap(bitmap);
        }
        //画一个圆
        public void drawCircle(View view) {
            init();
            //第一二参数表示圆心的坐标
            //第三个参数表示圆的半径
            canvas.drawCircle(250, 250, 250, paint);
            iv.setImageBitmap(bitmap);
        }
        //画一个扇形
        public void drawArc(View view) {
            init();
            RectF rectF = new RectF(20, 20, 500, 500);
            //第一个参数表示矩形
            //第二个参数为起始角度
            //第三参数表示扫过的角度
            //第四个参数表示扇形是否含有矩形的中线
            canvas.drawArc(rectF, -90, 180, true, paint);
            iv.setImageBitmap(bitmap);
        }
        //画一个多边形
        public void drawPath(View view) {
            init();
            Path path = new Path();
            //先移动到三角形的第一个点
            path.moveTo(250, 10);
            //再连线到第二个点
            path.lineTo(100, 300);
            //在第二、三个点之间画了一个扇形（以二三点之间连线为轴）
            RectF rectF = new RectF(100, 250, 400, 350);
            path.arcTo(rectF, 0, 180);
            //连线到第三个点
            path.lineTo(400, 300);
            //最后连线回第一个点
            path.lineTo(250, 10);
    
            canvas.drawPath(path, paint);
            iv.setImageBitmap(bitmap);
        }
        //画一个五角星
        public void drawStar(View view) {
            init();
            paint.setAntiAlias(true);
            Path path = new Path(); 
            float radian = degree2Radian(DEGREE);
            float radius_in = (float) (radius * Math.sin(radian / 2) / Math.cos(radian)); //中间五边形的半径
    
            path.moveTo((float) (radius * Math.cos(radian / 2)), 0);
            path.lineTo((float) (radius * Math.cos(radian / 2) + radius_in * Math.sin(radian)), (float) (radius - radius * Math.sin(radian / 2)));
            path.lineTo((float) (radius * Math.cos(radian / 2) * 2), (float) (radius - radius * Math.sin(radian / 2)));
            path.lineTo((float) (radius * Math.cos(radian / 2) + radius_in * Math.cos( radian /2)),(float) (radius + radius_in * Math.sin( radian /2)));
            path.lineTo((float) (radius * Math.cos(radian / 2) + radius * Math.sin(radian)), (float) (radius + radius * Math.cos(radian)));
            path.lineTo((float) (radius * Math.cos(radian / 2)), (float) (radius + radius_in));
            path.lineTo((float) (radius * Math.cos(radian / 2) - radius * Math.sin(radian)), (float) (radius + radius * Math.cos(radian)));
            path.lineTo((float) (radius * Math.cos(radian / 2) - radius_in * Math.cos( radian /2)), (float) (radius + radius_in * Math.sin(radian / 2)));
            path.lineTo(0, (float) (radius - radius * Math.sin(radian /2)));
            path.lineTo((float) (radius * Math.cos(radian / 2) - radius_in * Math.sin(radian)) , (float) (radius - radius * Math.sin(radian /2)));
    
            path.close();
            canvas.drawPath(path, paint); 
            iv.setImageBitmap(bitmap);
        }
        //初始化画布和画布的一些设置
        private void init() {
            bitmap = bitmap.createBitmap(500, 500, Config.ARGB_8888);
            canvas = new Canvas(bitmap);
            //设置画板的颜色
            canvas.drawColor(Color.BLACK);
            paint = new Paint();
    // paint.setStyle(Style.STROKE); //设置画笔风格为空心
            paint.setColor(Color.RED); //设置画笔的颜色
            paint.setStrokeWidth(5);    //设置画笔的粗细
            paint.setAntiAlias(true);   //抗锯齿
        }
        /** * 角度转弧度 * @param degree * @return */
        private float degree2Radian(float degree){
            return (float) (Math.PI * degree / 180);
        }
    }

[20160514204626031]: /images/20220722/e453af3fa08b4f289c996e768c1718f3.png