iPhone SDK：透明视图中的非透明子视图

Question

我有一个已添加到我的UIView的子视图。 想法是子视图是带有uibutton的悬停面板。 子视图的alpha值为0.2，因为用户需要能够看到其背后的内容。

问题是，当我将uibuttons添加到子视图时，它们从子视图继承了alpha（我希望按钮是不透明的，并且alpha为1.0）。 我试图通过遍历uibutton并将其alpha设置回1.0来解决此问题，但没有成功。 解决方案？

    // Create the subview and add it to the view
    topHoverView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 50)];
    topHoverView.backgroundColor = [UIColor blackColor];
    [topHoverView setAlpha:0.2];
    [self.view addSubview:topHoverView];

    // Add button 1
    button1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button1 setFrame:CGRectMake(20, 10, 80, 30)];
    [button1 setTitle:@"New" forState:UIControlStateNormal];
    [button1 addTarget:self action:@selector(button1Action:) forControlEvents:UIControlEventTouchUpInside];
    [topHoverView addSubview:button1];

    // Add button 2
    button2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button2 setFrame:CGRectMake(120, 10, 80, 30)];
    [button2 setTitle:@"Clear" forState:UIControlStateNormal];
    [button2 addTarget:self action:@selector(button2Action:) forControlEvents:UIControlEventTouchUpInside];
    [topHoverView addSubview:button2];

    // Add button 3
    button3 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button3 setFrame:CGRectMake(220, 10, 80, 30)];
    [button3 setTitle:@"Delete" forState:UIControlStateNormal];
    [button3 addTarget:self action:@selector(button3Action:) forControlEvents:UIControlEventTouchUpInside];
    [topHoverView addSubview:d button3];

    // Attempt to iterate through the subviews (buttons) to set their transparency back to 1.0
    for (UIView *subView in topHoverView.subviews) {
        subView.alpha = 1.0;
    }

Answer 1

您应该使用alpha 1.0和透明的背景色创建topHoverView。 然后添加一个黑色背景的子视图，该子视图用alpha 0.2覆盖整个视图，然后将按钮添加到pHoverView：

// Create the subview and add it to the view
topHoverView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 50)];
topHoverView.backgroundColor = [UIColor transparentColor];
[topHoverView setAlpha:1.0];
[self.view addSubview:topHoverView];

canvasView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 50)];
canvasView.backgroundColor = [UIColor blackColor];
[canvasViewView setAlpha:0.2];
[topHoverView.view addSubview:canvasView];

// Add button 1
button1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button1 setFrame:CGRectMake(20, 10, 80, 30)];
[button1 setTitle:@"New" forState:UIControlStateNormal];
[button1 addTarget:self action:@selector(button1Action:) forControlEvents:UIControlEventTouchUpInside];
[topHoverView addSubview:button1];

// Add button 2
button2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button2 setFrame:CGRectMake(120, 10, 80, 30)];
[button2 setTitle:@"Clear" forState:UIControlStateNormal];
[button2 addTarget:self action:@selector(button2Action:) forControlEvents:UIControlEventTouchUpInside];
[topHoverView addSubview:button2];

// Add button 3
button3 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button3 setFrame:CGRectMake(220, 10, 80, 30)];
[button3 setTitle:@"Delete" forState:UIControlStateNormal];
[button3 addTarget:self action:@selector(button3Action:) forControlEvents:UIControlEventTouchUpInside];
[topHoverView addSubview:d button3];

// Attempt to iterate through the subviews (buttons) to set their transparency back to 1.0
for (UIView *subView in topHoverView.subviews) {
    subView.alpha = 1.0;
}

Answer 2

代替

topHoverView.backgroundColor = [UIColor transparentColor];

，以下代码正确。

topHoverView.backgroundColor = [UIColor clearColor];