我在用
implementation 'androidx.activity:activity-ktx:1.2.0-alpha07'
implementation 'androidx.fragment:fragment-ktx:1.3.0-alpha07'
这是我的完整示例代码，展示了如何使用内置的 Android 结果合约从应用程序中拍摄照片并将其显示在 ImageView 中。
Note:我的解决方案使用视图绑定 https://developer.android.com/topic/libraries/view-binding
MainActivity的布局 XML 包括 (1) 定义按钮onTakePhotoClick as the onClick事件和（2）和ImageView来显示拍摄的照片。
<Button
android:id="@+id/take_photo_button"
style="@style/Button"
android:drawableStart="@drawable/ic_camera_on"
android:onClick="onTakePhotoClick"
android:text="@string/button_take_photo"
app:layout_constraintTop_toBottomOf="@id/request_all_button" />
...
<ImageView
android:id="@+id/photo_preview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
app:layout_constraintTop_toBottomOf="@id/take_video_button" />
In my MainActivity我做了以下事情：
- Defined
imageUri: Uri?它将被设置为所拍摄图像的 uriTakePicture()合同。
- 实施的
onTakePhotoClick()在启动之前检查必要的相机权限TakePicture()合同。
- Defined
takePictureRegistration: ActivityResultLauncher这实际上会启动在设备上拍照的请求。什么时候isSuccess返回为true然后我知道imageUri我之前定义的现在引用了我刚刚拍摄的照片。
- 定义了一个
takePicture: Runnable只是为了代码重用。请注意，第 2 个String参数传递给FileProvider.getUriForFile(context, authority, file)方法需要匹配authorities属性提供给<provider>在你的应用程序中AndroidManifest.xml.
- 为了完全透明，我还添加了显示如何使用的代码ActivityResultContracts.RequestPermission() https://developer.android.com/reference/androidx/activity/result/contract/ActivityResultContracts.RequestPermission请求用户访问相机的运行时权限。
private var imageUri: Uri? = null
/**
* Function for onClick from XML
*
* Check if camera permission is granted, and if not, request it
* Once permission granted, launches camera to take photo
*/
fun onTakePhotoClick(view: View) {
if (!checkPermission(Manifest.permission.CAMERA)) {
// request camera permission first
onRequestCameraClick(callback = takePicture)
} else {
takePicture.run()
}
}
private val takePicture: Runnable = Runnable {
ImageUtils.createImageFile(applicationContext)?.also {
imageUri = FileProvider.getUriForFile(
applicationContext,
BuildConfig.APPLICATION_ID + ".fileprovider",
it
)
takePictureRegistration.launch(imageUri)
}
}
private val takePictureRegistration =
registerForActivityResult(ActivityResultContracts.TakePicture()) { isSuccess ->
if (isSuccess) {
mBinding.photoPreview.setImageURI(imageUri)
}
}
/**
* Function for onClick from XML
*
* Launches permission request for camera
*/
fun onRequestCameraClick(view: View? = null, callback: Runnable? = null) {
registerForActivityResult(ActivityResultContracts.RequestPermission()) { isGranted: Boolean ->
// update image
mBinding.iconCameraPermission.isEnabled = isGranted
val message = if (isGranted) {
"Camera permission has been granted!"
} else {
"Camera permission denied! :("
}
Toast.makeText(this, message, Toast.LENGTH_SHORT).show()
if (isGranted) {
callback?.run()
}
}.launch(Manifest.permission.CAMERA)
}
为了完全透明ImageUtils实用程序类有createImageFile()方法定义如下并返回一个File?当给定上下文时。请注意，我使用外部文件目录作为 FileProvider 的存储目录。
object ImageUtils {
lateinit var currentPhotoPath: String
@Throws(IOException::class)
fun createImageFile(context: Context): File? {
// Create an image file name
val timeStamp: String = SimpleDateFormat("yyyyMMdd_HHmmss", Locale.US).format(Date())
val storageDir: File? = context.getExternalFilesDir(Environment.DIRECTORY_PICTURES)
return File.createTempFile(
"JPEG_${timeStamp}_", /* prefix */
".jpg", /* suffix */
storageDir /* directory */
).apply {
// Save a file: path for use with ACTION_VIEW intents
currentPhotoPath = absolutePath
}
}
}
不要忘记添加uses-permission, uses-feature and provider标签到AndroidManifest.
还要确保authorities属性提供给<provider>匹配传递给的第二个字符串参数FileProvider.getUriForFile(context, authority, file)方法。在我的示例中，我已将权限设置为包名称+“.fileprovider”。阅读更多关于FileProvider来自谷歌的文档 https://developer.android.com/reference/androidx/core/content/FileProvider.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.captech.android_activity_results">
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.camera" />
<application
...
<provider
android:name="androidx.core.content.FileProvider"
android:authorities="com.captech.android_activity_results.fileprovider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/file_paths" />
</provider>
</application>
</manifest>
My res/xml/file_paths如下所示。因为我正在使用getExternalFilesDir()，我正在使用<external-files-path>XML 中的标签。
Note:如果您不使用外部文件目录，您可能需要查找要在 XML 标记中指定的 FileProvider 存储目录.
<?xml version="1.0" encoding="utf-8"?>
<paths>
<external-files-path
name="my_images"
path="/" />
</paths>
结果将显示imageUri在图像视图中：
