ImageView的加載動畫自定義

要為ImageView添加自定義的加載動畫，可以通過創(chuàng)建一個自定義的Drawable類來實現(xiàn)。下面是一個簡單的示例代碼：

public class LoadingAnimationDrawable extends Drawable {

    private static final int ROTATION_SPEED = 180; // 旋轉(zhuǎn)速度，單位為度/秒
    private int mDegrees = 0;
    private boolean mIsRunning = false;

    private final Handler mHandler = new Handler();
    private final Runnable mUpdateFrameRunnable = new Runnable() {
        @Override
        public void run() {
            invalidateSelf();
            if (mIsRunning) {
                mHandler.postDelayed(this, 1000 / ROTATION_SPEED);
            }
        }
    };

    @Override
    public void draw(@NonNull Canvas canvas) {
        int width = getBounds().width();
        int height = getBounds().height();
        int centerX = width / 2;
        int centerY = height / 2;
        canvas.save();
        canvas.rotate(mDegrees, centerX, centerY);
        // 在畫布上繪制加載動畫
        // 這里以繪制一個旋轉(zhuǎn)的圓圈為例
        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(5);
        canvas.drawCircle(centerX, centerY, 50, paint);
        canvas.restore();
        mDegrees = (mDegrees + 1) % 360;
    }

    @Override
    public void setAlpha(int alpha) {
        // do nothing
    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {
        // do nothing
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }

    @Override
    public void start() {
        if (!mIsRunning) {
            mIsRunning = true;
            mHandler.post(mUpdateFrameRunnable);
        }
    }

    @Override
    public void stop() {
        if (mIsRunning) {
            mIsRunning = false;
            mHandler.removeCallbacks(mUpdateFrameRunnable);
        }
    }
}

然后，在使用ImageView時，可以通過設(shè)置該自定義的Drawable來顯示加載動畫：

LoadingAnimationDrawable loadingDrawable = new LoadingAnimationDrawable();
imageView.setImageDrawable(loadingDrawable);
loadingDrawable.start();

// 加載完成后停止動畫
loadingDrawable.stop();

通過以上方式，可以實現(xiàn)一個簡單的自定義加載動畫，并將其應(yīng)用到ImageView中。如果需要更復(fù)雜的加載動畫，可以在自定義Drawable中實現(xiàn)更多的繪制邏輯。