c# - 将布局保存到位图(Xamarin)

Question

我有布局，需要将它保存到位图

这是代码

public void Save()
{
    LinearLayout view = FindViewById<LinearLayout>(Resource.Id.badge);

    view.DrawingCacheEnabled = true;
    view.BuildDrawingCache();
    Bitmap layout = view.GetDrawingCache(true);

}

我将断点设置为 Bitmap layout = view.GetDrawingCache(true);，我发现它的布局为空。

我的错误在哪里，如何将布局保存为位图？

更新

我尝试像这样将 View 保存为位图

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        var bitmap2 = view.GetDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        return bitmap2;

    }

一切正常，bitmap2 正在返回。

但我还需要将它保存到 SD

我是这样写的

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        var bitmap2 = view.GetDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        var sdCardPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        var filePath = System.IO.Path.Combine(sdCardPath, "test.png");
        var stream = new FileStream(filePath, FileMode.Create);
        bitmap2.Compress(Bitmap.CompressFormat.Png, 100, stream);
        return bitmap2;

    }

并且有这个错误。

Object reference not set to an instance of an object.

Answer 1

把它改成这样:

public Bitmap CreateBitmapFromView(View view, bool autoScale = true)
{
    var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
    view.DrawingCacheEnabled = true;
    view.BuildDrawingCache(autoScale);
    var bitmap = view.GetDrawingCache(autoScale);
    view.DrawingCacheEnabled = wasDrawingCacheEnabled;
    return bitmap;
}

更新

尝试将var bitmap2定义为全局变量

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        var sdCardPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        var filePath = System.IO.Path.Combine(sdCardPath, "test.png");
        var stream = new FileStream(filePath, FileMode.Create);
        bitmap2.Compress(Bitmap.CompressFormat.Png, 100, stream);
        return bitmap2;
    }