Question

我正在尝试使用缩放功能创建一个自定义视图，但它在我的下面的代码中没有显示任何内容。因为这里请求的是我当前如何缩放位图，请注意我正在寻找另一种缩放方法整个画布。这是我的onDraw（）方法的细节，但是完整的方法在项目放置方面有更多的逻辑，在缩放之前我检查一个布尔标志，如果用户选择了缩放但我想你不想筛选那么多代码，所以我只是把相关的东西放在这里。

private final int bgColor = 8355711;
private Paint paint;
private Bitmap bgBitmap;
private float scaleFactor = 1;
private final float minScaleFactor = 0.25f, maxScaleFactor = 10f;
private ScaleGestureDetector scaleDetector;

public OratorView(Context context) {
    super(context, null, 0);
//  init(context);
}

public OratorView(Context context, AttributeSet set) {
    super(context, set, 0);
    init(context);
}

public OratorView(Context context, AttributeSet set, int defStyle) {
    super(context, set, defStyle);
    init(context);
}

private void init(Context context) {
    if (null == scaleDetector)
        this.scaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    this.paint = new Paint();
    this.paint.setColor(bgColor);
}

public void setBackground(Bitmap bitmap) {
    this.bgBitmap = bitmap;
    bgScaled = false;
}

private boolean bgScaled = false;

private void scaleBg() {
    if (null != bgBitmap) {
        if (bgBitmap.getWidth() > 0 && bgBitmap.getHeight() > 0) {
            float widthFactor = (float) bgBitmap.getWidth() / (float) getWidth();
            float heightFactor = (float) bgBitmap.getHeight() / (float) getHeight();
            float scale = widthFactor > heightFactor ? widthFactor : heightFactor;
            bgBitmap = Bitmap.createScaledBitmap(bgBitmap, (int) (bgBitmap.getWidth() / scale), (int) (bgBitmap.getHeight() / scale),
                    true);
            bgScaled = true;
        }
        invalidate();
    }
}

@Override
public void onDraw(Canvas c) {
    super.onDraw(c);
    c.save();
    c.scale(scaleFactor, scaleFactor);
    // fill background with solid color
    c.drawColor(bgColor);

    if (!bgScaled) {
        scaleBg();
    }
    // draw background image if any
    if (null != bgBitmap) {
        c.drawBitmap(bgBitmap, (getWidth() - bgBitmap.getWidth()) / 2, (getHeight() - bgBitmap.getHeight()) / 2, paint);
    }
    c.restore();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    scaleDetector.onTouchEvent(ev);
    return true;
}

private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scaleFactor *= detector.getScaleFactor();
        Log.d("OratorView", "onScale - scaleFactor=" + scaleFactor);
        if (scaleFactor >= maxScaleFactor && scaleFactor <= maxScaleFactor) {
            scaleFactor = Math.max(0.1f, Math.min(scaleFactor, 5.0f));
            invalidate();
        }
        return true;
    }
}

Answer 1

我认为问题出在您的ScaleListener.onScale方法中。这是我正在讨论的代码块：

 if (scaleFactor >= maxScaleFactor && scaleFactor <= maxScaleFactor) {
          scaleFactor = Math.max(0.1f, Math.min(scaleFactor, 5.0f));
          invalidate();
 }

只有scaleFactor == maxScaleFactor才会出现这种情况。由于如果此条件为真，您只是使视图无效，只要您没有将scaleFactor设置为10f，就不会重绘您的视图。

顺便说一句，我不明白为什么要将当前的比例因子乘以所选的比例因子。我建议将此作业更改为：

scaleFactor = detector.getScaleFactor();

Android上的自定义视图，缩放功能无效

1 个答案: