XAML=网格中的对象不可见

我现在正在学习XAML，我想创建一个简单的音乐播放器，但我有一个小问题。如果我定义第二，第三。。。栅格，此栅格中的对象不可见（仅第一个栅格中的对象可见）。你能帮我吗

<StackPanel>
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition></ColumnDefinition>
      </Grid.ColumnDefinitions>
      <Grid.RowDefinitions>
        <RowDefinition Height="53"></RowDefinition>
        <RowDefinition Height="75"></RowDefinition>
      </Grid.RowDefinitions>
      <Rectangle Fill="#333333"
                 HorizontalAlignment="Left"
                 Height="128"
                 Grid.RowSpan="2"
                 VerticalAlignment="Top"
                 Width="480"
                 Grid.ColumnSpan="4" />
      <Button CommandParameter="alarm"
              Click="PlaySound"
              VerticalContentAlignment="Center"
              Grid.Column="0"
              Grid.Row="1"
              Content="►"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="20" />
      <Button VerticalContentAlignment="Center"
              Grid.Column="1"
              Grid.Row="1"
              Content=" ▌▌"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="15" />
      <Button VerticalContentAlignment="Center"
              Grid.Column="2"
              Grid.Row="1"
              Content="■"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="25" />
      <TextBlock Grid.Row="0"
                 HorizontalAlignment="Left"
                 TextWrapping="Wrap"
                 Text="song_name"
                 VerticalAlignment="Top"
                 Grid.ColumnSpan="3"
                 Height="53"
                 Width="auto"
                 FontSize="30"
                 Margin="12,0,0,0" />
    </Grid>
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition Width="75"></ColumnDefinition>
        <ColumnDefinition></ColumnDefinition>
      </Grid.ColumnDefinitions>
      <Grid.RowDefinitions>
        <RowDefinition Height="53"></RowDefinition>
        <RowDefinition Height="75"></RowDefinition>
      </Grid.RowDefinitions>
      <Rectangle Fill="#333333"
                 HorizontalAlignment="Left"
                 Height="128"
                 Grid.RowSpan="2"
                 VerticalAlignment="Top"
                 Width="480"
                 Grid.ColumnSpan="4" />
      <Button CommandParameter="alarm"
              Click="PlaySound"
              VerticalContentAlignment="Center"
              Grid.Column="0"
              Grid.Row="1"
              Content="►"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="20" />
      <Button VerticalContentAlignment="Center"
              Grid.Column="1"
              Grid.Row="1"
              Content=" ▌▌"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="15" />
      <Button VerticalContentAlignment="Center"
              Grid.Column="2"
              Grid.Row="1"
              Content="■"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Width="75"
              Height="75"
              Style="{StaticResource Rounded}"
              FontFamily="Arial"
              FontSize="25" />
      <TextBlock Grid.Row="0"
                 HorizontalAlignment="Left"
                 TextWrapping="Wrap"
                 Text="song_name"
                 VerticalAlignment="Top"
                 Grid.ColumnSpan="3"
                 Height="53"
                 Width="auto"
                 FontSize="30"
                 Margin="12,0,0,0" />
    </Grid>
  </StackPanel>

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屏幕：

您的网格位置分配不明确

网格行和网格列在哪里

<Rectangle Fill="#333333" HorizontalAlignment="Left" Height="128" Grid.RowSpan="2" VerticalAlignment="Top" Width="480" Grid.ColumnSpan="4"/>

Grid.RowSpan=“2”Grid.columnsspan=“4”我添加了Grid.Row和Column。。。但还是一样的问题。第二个网格中的对象不显示您是否也使用更改更新了第二个网格？什么类型的XAML项目；WPF、Windows Phone、Silverlight？