Android: 使离屏位图在移动时可见

Question

我需要开始 activity 中间有两个圆形位图，它们应该立即动画并稍微移动到一边，这样一个位图的一部分就在屏幕外并且不可见。稍后，当用户离开 activity 时，它应该以相同的方式但向后动画（从一侧移动到中心）。

所以我实现了一个 class 将这些位图绘制在它们的主要位置（侧面），我现在遇到的问题是，当我为它们制作动画时，屏幕外的部分位图从未显示，所以在我的屏幕上我看到一个丑陋的移动位图，缺少一块。

位图是这样绘制的：

public class MyImageView extends ImageView {

    private Canvas offscreen;

    private static Bitmap pattern;
    private static Bitmap logo;

    private static int screenWidth, screenHeight; //The real size of the screen
    private static int patternDiameter, logoDiameter; //bitmaps' dimensions, both images are circles 

    private static float topPatternMargin, leftPatternMargin;
    private static float topLogoMargin, leftLogoMargin;

    public MyImageView (Context context, AttributeSet attrs) {
        super(context, attrs);

        screenWidth = getSize(context)[0];
        screenHeight = getSize(context)[1];

        patternDiameter = (int)(screenWidth * (1005.0/1280.0));
        logoDiameter = (int)(patternDiameter * (230.0/502.5));

        pattern = BitmapFactory.decodeResource(context.getResources(), R.drawable.start_pattern);
        pattern = Bitmap.createScaledBitmap(pattern, patternDiameter, patternDiameter, false);
        logo = BitmapFactory.decodeResource(context.getResources(), R.drawable.start_logo);
        logo = Bitmap.createScaledBitmap(logo, logoDiameter, logoDiameter, false);

        leftPatternMargin = (float) ((screenWidth) * (430.0/1280.0) - (patternDiameter/2.0));
        topPatternMargin = (float) ((screenHeight - patternDiameter)/2.0);
        leftLogoMargin = (float) (leftPatternMargin + patternDiameter/2.0 - logoDiameter/2.0);
        topLogoMargin = (float)(topPatternMargin + patternDiameter/2.0 - logoDiameter/2.0);

        offscreen = new Canvas(pattern);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        if(canvas==offscreen)
            super.onDraw(offscreen);

        else {

            super.draw(offscreen);

            canvas.drawBitmap(pattern, leftPatternMargin, topPatternMargin, null);
            canvas.drawBitmap(logo, leftLogoMargin, topLogoMargin, null);

        }

    }
}

所以我的问题是如何更改此代码（或可能是其他代码），以便当我创建此 class 的实例时，它的所有部分都对用户可见？

Answer 1

我在这里找到了答案：

When drawing outside the view clip bounds with Android: how do I prevent underling views from drawing on top of my custom view?

解决方案是将这一行添加到布局中：

android:clipChildren="false"

Android: 使离屏位图在移动时可见

Android: making offscreen bitmap visible when moved

java

android

android-animation

android-bitmap