是否将视图转换为位图而不在Android中显示？

我将尝试解释我到底需要做什么。

我有3个独立的屏幕，分别是A，B，C。还有一个名为“主屏幕”的屏幕，其中所有三个屏幕的位图都应在“图库”视图中显示，并且用户可以选择要进入的视图。

通过将所有代码仅放置在HomeScreen Activity中，我已经能够获取所有3个屏幕的位图并将其显示在Gallery视图中。现在，这使代码变得非常复杂，我想简化一下。

因此，我可以从HomeScreen调用另一个Activity而不显示它，而只是获取该屏幕的位图。例如，假设我只调用HomeScreen，它调用了活动A，B，C，则没有显示来自A，B，C的活动。它只是通过getDrawingCache（）给出了该屏幕的位图。然后我们可以在HomeScreen的Gallery视图中显示这些位图。

我希望我已经很清楚地解释了这个问题。

请让我知道这是否确实可行。

有一种方法可以做到这一点。您必须创建一个位图和一个画布并调用view.draw（canvas）;

这是代码：

public static Bitmap loadBitmapFromView(View v) {
    Bitmap b = Bitmap.createBitmap( v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888);                
    Canvas c = new Canvas(b);
    v.layout(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());
    v.draw(c);
    return b;
}

如果在大小之前未显示该视图，则该视图将为零。可以这样测量：

if (v.getMeasuredHeight() <= 0) {
    v.measure(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    Bitmap b = Bitmap.createBitmap(v.getMeasuredWidth(), v.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(b);
    v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
    v.draw(c);
    return b;
}

编辑：根据这篇文章，作为值传递不会做任何事情WRAP_CONTENTmakeMeasureSpec()（尽管对于某些视图类它确实起作用），并且推荐的方法是：

// Either this
int specWidth = MeasureSpec.makeMeasureSpec(parentWidth, MeasureSpec.AT_MOST);
// Or this
int specWidth = MeasureSpec.makeMeasureSpec(0 /* any */, MeasureSpec.UNSPECIFIED);
view.measure(specWidth, specWidth);
int questionWidth = view.getMeasuredWidth();

这是我的解决方案：

public static Bitmap getBitmapFromView(View view) {
    Bitmap returnedBitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(),Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(returnedBitmap);
    Drawable bgDrawable =view.getBackground();
    if (bgDrawable!=null) 
        bgDrawable.draw(canvas);
    else 
        canvas.drawColor(Color.WHITE);
    view.draw(canvas);
    return returnedBitmap;
}

请享用 ：）

试试这个，

/**
 * Draw the view into a bitmap.
 */
public static Bitmap getViewBitmap(View v) {
    v.clearFocus();
    v.setPressed(false);

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

    // Reset the drawing cache background color to fully transparent
    // for the duration of this operation
    int color = v.getDrawingCacheBackgroundColor();
    v.setDrawingCacheBackgroundColor(0);

    if (color != 0) {
        v.destroyDrawingCache();
    }
    v.buildDrawingCache();
    Bitmap cacheBitmap = v.getDrawingCache();
    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);

    return bitmap;
}

我知道这可能是一个过时的问题，但是我在获取任何一种适用于我的解决方案时遇到了问题。具体来说，我发现，如果在对视图进行夸大之后对视图进行了任何更改，则这些更改将不会合并到渲染的位图中。

这是最终为我的案例工作的方法。但是，请注意。在打电话之前，getViewBitmap(View)我夸大了视图并要求它以已知的尺寸进行布局。这是必需的，因为我的视图布局将使其高度/宽度为零，直到将内容放入内部为止。

View view = LayoutInflater.from(context).inflate(layoutID, null);
//Do some stuff to the view, like add an ImageView, etc.
view.layout(0, 0, width, height);

Bitmap getViewBitmap(View view)
{
    //Get the dimensions of the view so we can re-layout the view at its current size
    //and create a bitmap of the same size 
    int width = view.getWidth();
    int height = view.getHeight();

    int measuredWidth = View.MeasureSpec.makeMeasureSpec(width, View.MeasureSpec.EXACTLY);
    int measuredHeight = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.EXACTLY);

    //Cause the view to re-layout
    view.measure(measuredWidth, measuredHeight);
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());

    //Create a bitmap backed Canvas to draw the view into
    Bitmap b = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(b);

    //Now that the view is laid out and we have a canvas, ask the view to draw itself into the canvas
    view.draw(c);

    return b;
}

在这里找到了我的“魔法酱”：https : //groups.google.com/forum/#!topic/android-developers/BxIBAOeTA1Q

干杯，

李维

Android KTX中有一个很棒的Kotlin扩展功能： View.drawToBitmap(Bitmap.Config)

希望这可以帮助

View view="some view instance";        
view.setDrawingCacheEnabled(true);
Bitmap bitmap=view.getDrawingCache();
view.setDrawingCacheEnabled(false);

getDrawingCache()在API级别28中不推荐使用更新方法。因此，请针对API级别> 28寻找其他替代方法。

我认为这会更好一些：

/**
 * draws the view's content to a bitmap. code initially based on :
 * http://nadavfima.com/android-snippet-inflate-a-layout-draw-to-a-bitmap/
 */
@Nullable
public static Bitmap drawToBitmap(final View viewToDrawFrom, int width, int height) {
    boolean wasDrawingCacheEnabled = viewToDrawFrom.isDrawingCacheEnabled();
    if (!wasDrawingCacheEnabled)
        viewToDrawFrom.setDrawingCacheEnabled(true);
    if (width <= 0 || height <= 0) {
        if (viewToDrawFrom.getWidth() <= 0 || viewToDrawFrom.getHeight() <= 0) {
            viewToDrawFrom.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
            width = viewToDrawFrom.getMeasuredWidth();
            height = viewToDrawFrom.getMeasuredHeight();
        }
        if (width <= 0 || height <= 0) {
            final Bitmap bmp = viewToDrawFrom.getDrawingCache();
            final Bitmap result = bmp == null ? null : Bitmap.createBitmap(bmp);
            if (!wasDrawingCacheEnabled)
                viewToDrawFrom.setDrawingCacheEnabled(false);
            return result;
        }
        viewToDrawFrom.layout(0, 0, width, height);
    } else {
        viewToDrawFrom.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY));
        viewToDrawFrom.layout(0, 0, viewToDrawFrom.getMeasuredWidth(), viewToDrawFrom.getMeasuredHeight());
    }
    final Bitmap drawingCache = viewToDrawFrom.getDrawingCache();
    final Bitmap bmp = ThumbnailUtils.extractThumbnail(drawingCache, width, height);
    final Bitmap result = bmp == null || bmp != drawingCache ? bmp : Bitmap.createBitmap(bmp);
    if (!wasDrawingCacheEnabled)
        viewToDrawFrom.setDrawingCacheEnabled(false);
    return result;
}

使用上面的代码，如果要使用视图本身之一，则不必指定位图的大小（宽度和高度使用0）。

另外，如果希望将特殊视图（例如，SurfaceView，Surface或Window）转换为位图，则应考虑使用PixelCopy类。不过，它需要API 24及更高版本。我以前不知道该怎么做。

布局或视图到位图：

 private Bitmap createBitmapFromLayout(View tv) {      
    int spec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
    tv.measure(spec, spec);
    tv.layout(0, 0, tv.getMeasuredWidth(), tv.getMeasuredHeight());
    Bitmap b = Bitmap.createBitmap(tv.getMeasuredWidth(), tv.getMeasuredWidth(),
            Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(b);
    c.translate((-tv.getScrollX()), (-tv.getScrollY()));
    tv.draw(c);
    return b;
}

调用方法：

Bitmap src = createBitmapFromLayout(View.inflate(this, R.layout.sample, null)/* or pass your view object*/);

view.setDrawingCacheEnabled(true);
Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache());
view.setDrawingCacheEnabled(false);