android桌面动态时钟

您可以使用Android中的`SurfaceView`和`Canvas`来创建动态时钟。

首先，您需要创建一个`SurfaceView`并将其添加到您的布局中。然后，您可以使用`Canvas`在`SurfaceView`上绘制时钟的各个部分，例如时针、分针和秒针。

以下是一个简单的示例代码：

public class ClockView extends SurfaceView implements SurfaceHolder.Callback, Runnable {

    private Thread thread;
    private boolean isRunning;

    private Paint paint;
    private RectF rect;

    public ClockView(Context context) {
        super(context);
        init();
    }

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

    public ClockView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        getHolder().addCallback(this);

        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setStrokeCap(Paint.Cap.ROUND);

        rect = new RectF();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        isRunning = true;
        thread = new Thread(this);
        thread.start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // Do nothing
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        isRunning = false;

        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        while (isRunning) {
            if (!getHolder().getSurface().isValid()) {
                continue;
            }

            Canvas canvas = getHolder().lockCanvas();

            // Clear canvas
            canvas.drawColor(Color.BLACK);

            // Draw clock
            drawClock(canvas);

            getHolder().unlockCanvasAndPost(canvas);

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private void drawClock(Canvas canvas) {
        int width = canvas.getWidth();
        int height = canvas.getHeight();
        int cx = width / 2;
        int cy = height / 2;

        // Draw hour hand
        paint.setStrokeWidth(10);
        int hours = Calendar.getInstance().get(Calendar.HOUR);
        int minutes = Calendar.getInstance().get(Calendar.MINUTE);
        float hourAngle = ((hours * 60) + minutes) / 2f;
        float hourRadians = (float) Math.toRadians(hourAngle - 90);
        float hourX = (float) (cx + (100 * Math.cos(hourRadians)));
        float hourY = (float) (cy + (100 * Math.sin(hourRadians)));
        canvas.drawLine(cx, cy, hourX, hourY, paint);

        // Draw minute hand
        paint.setStrokeWidth(6);
        float minuteAngle = minutes * 6f;
        float minuteRadians = (float) Math.toRadians(minuteAngle - 90);
        float minuteX = (float) (cx + (150 * Math.cos(minuteRadians)));
        float minuteY = (float) (cy + (150 * Math.sin(minuteRadians)));
        canvas.drawLine(cx, cy, minuteX, minuteY, paint);

        // Draw second hand
        paint.setStrokeWidth(2);
        paint.setColor(Color.RED);
        float seconds = Calendar.getInstance().get(Calendar.SECOND);
        float secondAngle = seconds * 6f;
        float secondRadians = (float) Math.toRadians(secondAngle - 90);
        float secondX = (float) (cx + (200 * Math.cos(secondRadians)));
        float secondY = (float) (cy + (200 * Math.sin(secondRadians)));
        canvas.drawLine(cx, cy, secondX, secondY, paint);

        // Draw ticks
        paint.setStrokeWidth(3);
        paint.setColor(Color.WHITE);
        for (int i = 0; i < 60; i++) {
            float tickAngle = i * 6f;
            float tickRadians = (float) Math.toRadians(tickAngle - 90);
            float tickX1 = cx + (190 * (float) Math.cos(tickRadians));
            float tickY1 = cy + (190 * (float) Math.sin(tickRadians));
            float tickX2 = cx + (200 * (float) Math.cos(tickRadians));
            float tickY2 = cy + (200 * (float) Math.sin(tickRadians));
            canvas.drawLine(tickX1, tickY1, tickX2, tickY2, paint);
        }

        // Draw center circle
        paint.setColor(Color.WHITE);
        canvas.drawCircle(cx, cy, 10, paint);
    }
}

在这个例子中，我们创建了一个名为`ClockView`的自定义`SurfaceView`，并实现了`SurfaceHolder.Callback`和`Runnable`接口。`SurfaceHolder.Callback`用于在`SurfaceView`被创建、改变和销毁时进行处理，而`Runnable`用于在后台线程中更新时钟。

`init()`方法用于初始化一些变量，包括`Paint`对象和一个`RectF`对象，后者用于绘制圆形。

`surfaceCreated()`方法用于启动后台线程，从而开始更新时钟。`surfaceChanged()`方法不执行任何操作，而`surfaceDestroyed()`方法用于停止后台线程。

`run()`方法是后台线程的主要逻辑。在其中，我们使用`lockCanvas()`方法获取一个`Canvas`对象，并在其中绘制时钟。最后，我们使用`unlockCanvasAndPost()`方法将`Canvas`对象提交给`SurfaceView`以进行显示。

`drawClock()`方法用于绘制时钟的各个部分，包括时针、分针、秒针、刻度和中心圆。

最后，在您的布局中添加`ClockView`即可显示动态时钟。