public abstract class BaseView extends View {  private control thread;  public BaseView(Context context, AttributeSet attrs) {    super(context, attrs);  }  public BaseView(Context context) {    super(context);  }  //封裝,構造畫面,子類繼承后需要重寫  protected abstract void drawsub(Canvas canvas);  //封裝移動方法,子類繼承后需要重寫  protected abstract void move();  //封裝的初始化方法  protected abstract void init();  @Override  protected final void onDraw(Canvas canvas) {    //啟動線程    if (thread ==null) {      thread = new control();      thread.start();    }else {      drawsub(canvas);    }  }  public class control extends Thread{    @Override    public void run() {      init();      while(true){        move();        //相當于刷新畫布        postInvalidate();        try {          sleep(30);        } catch (InterruptedException e) {          e.printStackTrace();        }      }    }  }}

public class RainItem {  private int height;  private int width;  private float startX;  private float startY;  private float stopX;  private float stopY;  private float sizeX;  private float sizeY;  private float of = 0.5f;  private Paint paint;  private Random random = new Random();  public RainItem(int height,int width) {    this.height = height;    this.width = width;    init();  }  public void init() {    //startx和y對應的分別是起止位置    sizeX = 1 + random.nextInt(10);    sizeY = 10 + random.nextInt(20);    startX = random.nextInt(width);    startY = random.nextInt(height);    stopX = startX + sizeX;    stopY = startY + sizeY;    of = (float) (0.2 + random.nextFloat());    paint = new Paint();  }  /**   * 繪畫雨滴   * @param canvas   */  public void draw(Canvas canvas) {    paint.setARGB(255, random.nextInt(255), random.nextInt(255), random.nextInt(255));    canvas.drawLine(startX, startY, stopX, stopY, paint);  }  /**   * 雨滴的移動行為   */  public void movestep() {    //size*of這個是用來控制速度,所謂的速度就是線條增加的速度    startX += sizeX*of;    stopX += sizeX*of;    startY += sizeY*of;    stopY += sizeY*of;    //如果超出邊界則重新運行    if (startY>height) {      init();    }  }}

public class Rainplay extends BaseView {  List<RainItem> list = new ArrayList<RainItem>();  //控制雨滴的數量  private int num = 80;  public Rainplay(Context context) {    super(context);  }  public Rainplay(Context context, AttributeSet attrs) {    super(context, attrs);    //與xml鏈接起來    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.RainView);    num = ta.getInteger(R.styleable.RainView_rainnum,80);    ta.recycle();  }  @Override  protected void drawsub(Canvas canvas) {    for (RainItem item : list) {      item.draw(canvas);    }  }  @Override  protected void move() {    for (RainItem item : list) {      item.movestep();    }  }  /**   * 因為獲取長寬是放在layout之后才可以獲取,所以需要   * 放在線程里面初始化   */  @Override  protected void init() {    for (int i = 0; i < num; i++) {      RainItem item = new RainItem(getHeight(), getWidth());      list.add(item);    }      }}

<?xml version="1.0" encoding="utf-8"?><resources>  <declare-styleable name = "RainView">    <attr name="rainnum" format="integer"/>   </declare-styleable></resources>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  xmlns:an="http://schemas.android.com/apk/res/com.niuli.Rain"  android:layout_width="match_parent"  android:layout_height="match_parent"   >  <com.niuli.Rain.Rainplay     android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="#ff000000"    an:rainnum = "100"/></FrameLayout>