Question

我正在以编程方式创建一个永远不会被绘制到屏幕上的view（view不会从XML中膨胀或在onCreate期间在屏幕上设置。相反，我想创建一个用于图像的视图位图。但是，我无法获得位图/正确的位图。

我查看了网站，并使用了各种问题，例如：Converting a view to Bitmap without displaying it in Android?。最初，我使用了以下代码：

public Bitmap loadBitmapFromView(View v)
{
    Bitmap bitmap = Bitmap.createBitmap(v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888); //v.getWidth() and v.getHeight() are 0 since view isn't drawn
    Canvas canvas = new Canvas(bitmap);
    v.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
    v.layout(0, 0, v.getLayoutParams().width, v.getLayoutParams().height); //v.getMeasuredHeight() and v.getMeasuredWidth() are zero --- not sure why?
    v.draw(canvas);
    return bitmap;
}

此代码创建了一个位图，但它始终为空，并且没有view作为图像。然后我尝试了第三个答案（@Dwivedi Ji），为方便起见：

private Bitmap getViewBitmap(View v) {
    v.clearFocus();
    v.setPressed(false);
    v.setDrawingCacheEnabled(true);

    boolean willNotCache = v.willNotCacheDrawing();
    v.setWillNotCacheDrawing(false);

    int color = v.getDrawingCacheBackgroundColor();
    v.setDrawingCacheBackgroundColor(0);

    if (color != 0) {
        v.destroyDrawingCache();
    }
    v.buildDrawingCache();
    Bitmap cacheBitmap = v.getDrawingCache(); //This was always null
    if (cacheBitmap == null) { 
        Log.e(TAG, "failed getViewBitmap(" + v + ")", new RuntimeException());
        return null;
    }

    Bitmap bitmap = Bitmap.createBitmap(cacheBitmap);

    // Restore the view
    v.destroyDrawingCache();
    v.setWillNotCacheDrawing(willNotCache);
    v.setDrawingCacheBackgroundColor(color);
    v.setDrawingCacheEnabled(false);

    return bitmap;
}

v.getDrawingCache()调用始终返回null，这使我没有位图。

如何使用view图像获取此位图？我为这个冗长的问题道歉（有点新发布在这里，如果您需要其他信息/说明，请告诉我）。

提前致谢！

修改

我尝试在位图中创建的类如下：

public class CircleView extends View
{
    ... //Constructors - Nothing special here

    @Override protected void onDraw(Canvas canvas)
    {
        canvas.drawColor(0x00000000);

        if(m_lineWidthPx == 0) //Previously set
            return;

        float centerX = getMeasuredHeight() / 2.f;
        float centerY = getMeasuredHeight() / 2.f;
        float radius = getMeasuredWidth() / 2.f - (m_lineWidthPx) / 2.f;
        m_paint.setStrokeWidth(m_lineWidthPx); //m_paint is instantiated in the constructors
        m_paint.setStyle(Paint.Style.STROKE);
        m_paint.setAntiAlias(true);
        canvas.drawCircle(centerX, centerY, radius, m_paint);
    }
}

课堂上没有太多，基本上画一个圆圈。我省略了构造函数，因为那里没有特殊的东西。他们只需设置m_lineWidthPx变量并实例化m_paint变量。

Answer 1

检查你的位图的大小，是不是0x0 pt？

我使用这种方法来做到这一点：

public static Bitmap getBitmapFromView(View view){

    view.measure(LinearLayout.LayoutParams.WRAP_CONTENT,
                 LinearLayout.LayoutParams.WRAP_CONTENT);

    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());

    Bitmap bitmap = Bitmap.createBitmap(view.getWidth(),
                                        view.getHeight(),
                                        Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(bitmap);
    view.draw(c);
    return bitmap;
}

Answer 2

我需要在一段时间之前从View创建一个位图。经过大量的测试/失败后，我终于开始使用这种方法：

public static Bitmap getBitmapFromView(View view) {
    view.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
    Bitmap bitmap = Bitmap.createBitmap(view.getMeasuredWidth(), view.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
    view.draw(canvas);
    return bitmap;
}

创建一个永远不会被绘制的视图的位图

2 个答案: