Android_手机桌面开发

public class LiveWallpaper extends WallpaperService
{
	// 记录用户触碰点的位图
	private Bitmap heart;
	// 实现WallpaperService必须实现的抽象方法
	@Override
	public WallpaperService.Engine onCreateEngine()
	{
		// 加载心形图片
		heart = BitmapFactory.decodeResource(getResources(), R.drawable.heart);
		// 返回自定义的Engine
		return new MyEngine();
	}

	class MyEngine extends WallpaperService.Engine
	{
		// 记录程序界面是否可见
		private boolean mVisible;
		// 记录当前当前用户动作事件的发生位置
		private float mTouchX = -1f;
		private float mTouchY = -1f;
		// 记录当前需要绘制的矩形的数量
		private int count = 1;
		// 记录绘制第一个矩形所需坐标变换的X、Y坐标的偏移
		private float originX = 0f;
		private float originY = 100f;
		private float cubeHeight = 0f;
		private float cubeWidth = 0f;
		// 定义画笔
		private Paint mPaint = new Paint();
		// 定义一个Handler
		private Handler mHandler = new Handler();
		// 用于记录屏幕大小
		private DisplayMetrics dis = new DisplayMetrics();
		// 定义一个周期性执行的任务
		private Runnable drawTarget = this::drawFrame;

		@Override
		public void onCreate(SurfaceHolder surfaceHolder)
		{
			super.onCreate(surfaceHolder);
			// 初始化画笔
			mPaint.setARGB(76, 0, 0, 255);
			mPaint.setAntiAlias(true);
			mPaint.setStyle(Paint.Style.FILL);
			// 根据屏幕宽度设置动态壁纸的起点位置的X坐标
			WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
			wm.getDefaultDisplay().getMetrics(dis);
			originX = dis.widthPixels / 3;
			originY = dis.heightPixels / 10;
			cubeHeight = dis.widthPixels / 4;
			cubeWidth = dis.widthPixels / 8;
			// 设置处理触摸事件
			setTouchEventsEnabled(true);
		}

		@Override
		public void onDestroy()
		{
			super.onDestroy();
			// 删除回调
			mHandler.removeCallbacks(drawTarget);
		}

		@Override
		public void onVisibilityChanged(boolean visible)
		{
			mVisible = visible;
			// 当界面可见时，执行drawFrame()方法
			if (visible)
			{
				// 动态地绘制图形
				drawFrame();
			}
			else
			{
				// 如果界面不可见，删除回调
				mHandler.removeCallbacks(drawTarget);
			}
		}

		@Override
		public void onOffsetsChanged(float xOffset, float yOffset,
									 float xStep, float yStep, int xPixels, int yPixels)
		{
			drawFrame();
		}

		@Override
		public void onTouchEvent(MotionEvent event)
		{
			// 如果检测到滑动操作
			if (event.getAction() == MotionEvent.ACTION_MOVE)
			{
				mTouchX = event.getX();
				mTouchY = event.getY();
			}
			else
			{
				mTouchX = -1f;
				mTouchY = -1f;
			}
			super.onTouchEvent(event);
		}

		// 定义绘制图形的工具方法
		private void drawFrame()
		{
			// 获取该壁纸的SurfaceHolder
			SurfaceHolder holder = getSurfaceHolder();
			Canvas c = null;
			try
			{
				// 对画布加锁
				c = holder.lockCanvas();
				if (c != null)
				{
					// 绘制背景色
					c.drawColor(-0x1);
					// 在触碰点绘制心形
					drawTouchPoint(c);
					// 设置画笔的透明度
					mPaint.setAlpha(76);
					c.translate(originX, originY);
					// 采用循环绘制count个矩形
					for (int i = 0; i < count; i++) // ①
					{
						c.translate((cubeHeight * 2 / 3), 0f);
						c.scale(0.95f, 0.95f);
						c.rotate(20f);
						c.drawRect(0f, 0f, cubeHeight, cubeWidth, mPaint);
					}
				}
			}
			finally
			{
				if (c != null) holder.unlockCanvasAndPost(c);
			}
			mHandler.removeCallbacks(drawTarget);
			// 调度下一次重绘
			if (mVisible)
			{
				count++;
				if (count > 50)
				{
					originX = new Random().nextInt(dis.heightPixels * 2 / 3);
					originY = new Random().nextInt(dis.heightPixels / 5);
					count = 1;
					try
					{
						Thread.sleep(500);
					}
					catch (InterruptedException e)
					{
						e.printStackTrace();
					}
				}
				// 指定0.1秒后重新执行drawTarget一次
				mHandler.postDelayed(drawTarget, 100);  // ②
			}
		}

		// 在屏幕触碰点绘制位图
		private void drawTouchPoint(Canvas c)
		{
			if (mTouchX >= 0 && mTouchY >= 0)
			{
				// 设置画笔的透明度
				mPaint.setAlpha(255);
				c.drawBitmap(heart, mTouchX, mTouchY, mPaint);
			}
		}
	}
}