54、Android 粒子效果之雨（下雨的效果）

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;

/**
 * 基类
 */
public abstract class BaseView extends View {
    private MyThread thread;
    private boolean running = true;

    public BaseView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public BaseView(Context context) {
        super(context);
    }

    protected abstract void drawSub(Canvas canvas);
    protected abstract void logic();
    protected abstract void init();
    
    class MyThread extends Thread {
        @Override
        public void run() {
            init();
            while (running) {
                logic();
                postInvalidate();
                try {
                    Thread.sleep(30);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Override
    protected final void onDraw(Canvas canvas) {
        if (thread == null) {
            thread = new MyThread();
            thread.start();
        } else {
            drawSub(canvas);
        }
    }

    @Override
    protected void onDetachedFromWindow() {
        running = false;
        super.onDetachedFromWindow();
    }

}

 1   import android.content.Context;
 2 import android.graphics.Canvas;
 3 import android.graphics.Paint;
 4 import android.util.AttributeSet;
 5 
 6 public class RainView extends BaseView {
 8     private float startX;
 9     private float startY;
10     private float stopX;
11     private float stopY;
12     private float sizeX;
13     private float sizeY;
14     private Paint paint;
15 
16     public RainView(Context context, AttributeSet attrs) {
17         super(context, attrs);
19         // 角度。
20         sizeX = 10;
21         sizeY = 30;
22         // 以下是 初始化直线的坐标。
23         startX = 100;
24         startY = 0;
25         // 改变 角度的直线。
26         stopX = startX + sizeX;
27         stopY = startY + sizeY;
28 
29         paint = new Paint();
30         // 把直线 设置成白色。
31         paint.setColor(0xffffffff);
32     }
33 
34     public RainView(Context context) {
35         super(context);
36     }
37 
38     @Override
39     protected void drawSub(Canvas canvas) {
40         // 绘制一条直线
41         canvas.drawLine(startX, startY, stopX, stopY, paint);
42     }
43 
44     @Override   /* 让直线动起来 **/ 
45     protected void logic() {
46 
47         //倍率，通过倍率来改变速度。
48         float opt = 0.5f;
49 
50         startX += sizeX * opt;
51         stopX += sizeX * opt;
52 
53         startY += sizeY * opt;
54         stopY += sizeY * opt;
55 
56         // 当直线走出屏幕的时候，变为初始位置。
57         if (startY > getHeight()) {
58             startX = 100;
59             startY = 0;
60             stopX = startX + 10;
61             stopY = startY + 30;
62         }
63     }
64 
65 }