[移动开发]Android 简单快速 实现 满天星辰

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.util.AttributeSet;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import androidx.annotation.NonNull;
import java.util.Random;

public class MySurfaceView extends SurfaceView implements Runnable, SurfaceHolder.Callback {
    private final String TAG = this.getClass().getName();
    private final SurfaceHolder mHolder;

    Star[] stars = new Star[200];
    Paint paint = new Paint();
    Random random = new Random();

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

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

    public MySurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        mHolder = getHolder();
        mHolder.addCallback(this);

        paint.setAntiAlias(true);
        paint.setTextSize(80);
        paint.setColor(Color.WHITE);

        //初始化 星星
        for (int i = 0; i < stars.length; i++) {
            stars[i] = new Star();
        }
    }

    private void drawStar(Canvas canvas) {
        for (Star s : stars) {
            if (s.x == 0) {
                s.x = random.nextInt(getWidth());
                s.y = random.nextInt(getHeight());
            }

            s.smoothTwinkle();

            canvas.drawCircle(s.x, s.y, s.r, paint);
        }
    }

    @Override
    public void surfaceCreated(@NonNull SurfaceHolder holder) {
        Log.i(TAG, "surfaceCreated=");
        setWillNotDraw(false);
        new Thread(this).start();
    }

    @Override
    public void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {
        Log.i(TAG, "surfaceChanged=");
    }

    @Override
    public void surfaceDestroyed(@NonNull SurfaceHolder holder) {
        Log.i(TAG, "surfaceDestroyed=");
    }

    //第一种方法 使用surfaceview 绘制
    @Override
    public void run() {
        try {//try catch 用途：home键 或 息屏 时 ，mHolder 和 canvas 会报错

            Canvas canvas = mHolder.lockCanvas();
            //SurfaceView 清屏
            canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);

            drawStar(canvas);

            mHolder.unlockCanvasAndPost(canvas);
   
            postDelayed(this, 50);
        }catch (Exception e){
            Log.e(TAG,"run-ex="+e.getMessage());
        }
    }

    //第二种方法 使用 view 本身绘制
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        // drawStar(canvas);
        //postInvalidateDelayed(50);
    }

    class Star {
        int x, y;
        float r = new Random().nextInt(5) + 1;

        float fixR = 0.5f;
        float maxR = 5;
        float minR = 1;
        boolean isRadd = false;

        //闪烁
        public void twinkle(){
            r=random.nextInt(5)+1;
        }

        //平滑闪烁
        public void smoothTwinkle(){
            if (isRadd) {
                r += fixR;
                if (r > maxR) {
                    r = maxR;
                    isRadd = false;
                }
            } else {
                r -= fixR;
                if (r < minR) {
                    r = minR;
                    isRadd = true;
                }
            }
        }
    }
}

demo 下载地址：https://download.csdn.net/download/qq_29364417/80805271