Setting a Button’s Image

本文介绍如何为不同类型的按钮设置正常和交替图像,并提供了具体的代码示例。还详细说明了如何在XIB视图中设置定制按钮及各状态下的图像。

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A button can have two images associated with it: normal and alternate. If the button type is NSMomentaryPushInButton , NSPushOnPushOffButton , NSMomentaryLightButton , or NSOnOffButton , only the normal image is ever displayed. If the button type is NSMomentaryChangeButton or NSToggleButton , the normal image is displayed when the button’s state is off (NSOffState ) and the alternate image is displayed when the button’s state is on or mixed (NSOnState . or NSMixedState ). If you want a button to display different image for all three states, you must subclass NSButton . (Although switch and radio buttons can display different images for all three states, there is no public interface for this feature.)

To set the normal image, use setImage: . To set the alternate image, use setAlternateImage: .

Note:  If a button is a checkbox or a radio button, do not change its images. The images for these buttons are system-defined and changing them could lead to unpredictable results. If you want a switch or radio button with a customized appearance, either customize a toggle button (a button whose type is NSToggleButton ) or subclass NSButton .

 

Example:

NSButton *btn = [[NSButton alloc] initWithFrame: frame];

btn.setImage:[UIImage imageWithContentOfFile:path];

btn.setAlternateImage:[UIImage imageWithContentOfFile:path1];

 

Open the XIB view. Double click on the view (it will be a xib file) to open it up.

Add UIButton. Drag an UIButton from the library onto your view.

Change the button’s type to custom. Select the UIButton and then use the attributes applet to change the button type to “custom”.

Add images to button. Use the drop down box a near the top of the applet to change the attributes for each button state. Assign a different image to correspond to each state.

 

 

To set the position for a button’s image, use setImagePosition: , with one of the following values below. The default is NSNoImage

NSNoImage NSNoImage

NSImageOnly NSImageOnly

NSImageOverlaps NSImageOverlaps

 

 

NSImageLeft NSImageLeft

NSImageRight NSImageRight

 

NSImageBelow NSImageBelow

NSImageAbove NSImageAbove

### ImagePreview 功能介绍 ImagePreview 是一种用于展示图片预览的功能,在现代移动开发框架中广泛应用。对于 Android 平台而言,Jetpack Compose 提供了一个简洁高效的 API 来实现这一功能[^2]。 通过 `rememberImagePicker` 和其他辅助函数可以轻松集成图片选择器,并且能够快速构建一个响应式的界面来显示所选图片。下面是一个简单的例子说明如何创建一个基本的 ImagePreview 组件: ```kotlin import androidx.compose.foundation.Image import androidx.compose.foundation.clickable import androidx.compose.foundation.layout.* import androidx.compose.material.Button import androidx.compose.material.Text import androidx.compose.runtime.* import androidx.compose.ui.Modifier import androidx.compose.ui.unit.dp import coil.compose.rememberAsyncImagePainter import android.Manifest.permission.READ_EXTERNAL_STORAGE import com.google.accompanist.permissions.* @Composable fun ImagePreviewExample() { var imageUri by remember { mutableStateOf<String?>(null) } PermissionRequired( permission = READ_EXTERNAL_STORAGE, rational = { Text("Need storage access to pick an image") }, deniedContent = { Text("Permission Denied!") }) { Column(modifier = Modifier.padding(16.dp)) { Button(onClick = { // Here you would open the gallery or camera using some library like PhotoView. // For simplicity, we're just setting a dummy URI here. imageUri = "content://dummy/image" }) { Text(text = "Pick Image") } Spacer(modifier = Modifier.height(16.dp)) if (imageUri != null) { Box(modifier = Modifier.size(200.dp).clickable {}) { Image( painter = rememberAsyncImagePainter(imageUri), contentDescription = null, modifier = Modifier.fillMaxSize() ) } } else { Text("No image selected.") } } } } ``` 此代码片段展示了如何使用 Jetpack Compose 创建一个带有按钮触发的选择图片操作的应用程序。当用户点击“Pick Image”按钮时,理论上应该打开相册或相机选取一张照片;为了简化示例,这里只是模拟设置了 Uri 地址。一旦选择了图片,则会在界面上呈现该图片作为预览。
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