Android问题将带有子项的ViewGroup转换为位图

Question

我正在使用Canvas将ViewGroup(RelativeLayout)成功转换为Bitmap.但是,当绘制发生时,我只看到ViewGroup的背景可绘制而不是它的子(两个TextViews)应该使用像FILL_PARENT这样的规则在RelativeLayout中布局.

RelativeLayout使用以下静态函数创建:

public static RelativeLayout createProgrammeView(Context context, int width, int height, String title, String time) {
    RelativeLayout.LayoutParams params;

    // Layout Root View (RelativeLayout)
    RelativeLayout rlv = new RelativeLayout(context);
    params = new RelativeLayout.LayoutParams(width, height);
    rlv.setLayoutParams(params);
    rlv.setPadding(3, 3, 3, 3);
    rlv.setBackgroundResource(R.drawable.background);

    // Layout Title
    TextView tv = new TextView(context);
    params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.FILL_PARENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
    params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
    params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
    tv.setId(R.id.title);
    tv.setLayoutParams(params);
    tv.setGravity(Gravity.CENTER_VERTICAL);
    tv.setSingleLine(true);
    tv.setEllipsize(TruncateAt.END);
    tv.setTextColor(Color.parseColor("#fff"));
    tv.setTextSize(11);
    tv.setText(title);
    rlv.addView(tv);

    // Layout Start Time
    tv = new TextView(context);
    params = new RelativeLayout.LayoutParams(16, RelativeLayout.LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.BELOW, R.id.title);
    params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
    params.setMargins(0, 4, 0, 0);
    tv.setId(R.id.time);
    tv.setLayoutParams(params);
    tv.setGravity(Gravity.CENTER_VERTICAL);
    tv.setSingleLine(true);
    tv.setEllipsize(null);
    tv.setTextColor(Color.parseColor("#fff"));
    tv.setTextSize(10);
    tv.setText(time);
    rlv.addView(tv);
    }

    return rlv;
}

然后我使用以下内容将RelativeLayout转换为位图:

public static Bitmap loadBitmapFromView(RelativeLayout v) {
    Bitmap b = Bitmap.createBitmap(v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.RGB_565);
    Canvas c = new Canvas(b);
    v.draw(c);
    return b;
}

正如预期的那样,这给了我一个很好的Bitmap,我需要的背景是drawable,但是孩子们不在位图中.我将这些函数称为构建一个大图像,然后将其绘制到我的活动中的自定义视图中.

这是调用静态函数的循环:

public static void renderViews(final Context context) {
    largeBitmap = Bitmap.createBitmap(largeWidth, largeHeight, Bitmap.Config.RGB_565);
    Canvas largeCanvas = new Canvas(largeBitmap);

    for (int i = 0; i < items.size(); i++) {
        int leftMargin = ...SOME CALCULATIONS...;

        RelativeLayout newView = createProgrammeView(context, width, rowHeight, "Title", "21:00");
        Bitmap newViewBitmap = loadBitmapFromView(newView);

        largeCanvas.drawBitmap(newViewBitmap, leftMargin, 0, new Paint());
    }

    myCustomView.invalidate();
}

我的自定义视图会覆盖onDraw()函数:

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawBitmap(largeBitmap, 0, 0, null);
}

从我所看到的,我相信这是因为Android没有在子视图上调用measure().我试过手动调用它,但这并没有解决问题.

所以,我想我想知道的是,我如何实现将带孩子的RelativeLayout转换为Bitmap并让Android测量孩子,以便他们尊重他们的相对布局规则.

非常感谢能够帮助我解决这个问题的人.

抢

Answer 1

问题是您没有测量和布局容器.你必须打电话v.measure(widthSpec, heightSpec),然后v.layout(left, top, right, bottom)在绘图之前可以工作.第一种方法将确保视图知道您希望它有多大,第二种方法将确保子项正确定位.

在你的情况下,你会做:

v.measure(MeasureSpec.makeMeasureSpec(v.getLayoutParams().width, MeasureSpec.EXACTLY),
        MeasureSpec.makeMeasureSpec(v.getLayoutParams().height, MeasureSpec.EXACTLY));
v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());

Bitmap b = Bitmap.createBitmap(v.getWidth(), v.getHeight(), Bitmap.Config.RGB_565);
Canvas c = new Canvas(b);
v.draw(c);