这篇文章主要介绍“Android动态权限申请功能怎么实现”,在日常操作中,相信很多人在Android动态权限申请功能怎么实现问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”Android动态权限申请功能怎么实现”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
使用
为了解决这个痛点,我封装出了两个方法,用于随时随地快速的动态申请权限,我们先来看看我们的封装方法是如何调用的:
activity.requestPermission(Manifest.permission.CAMERA, onPermit = { //申请权限成功 Do something }, onDeny = { shouldShowCustomRequest -> //申请权限失败 Do something if (shouldShowCustomRequest) { //用户选择了拒绝并且不在询问,此时应该使用自定义弹窗提醒用户授权(可选) } })
这样是不是非常的简单便捷?申请和结果回调都在一个方法内处理,并且支持随用随调。
方案
那么,这么方便好用的方法是怎么实现的呢?不知道小伙伴们在平时开发中有没有注意到过,当你调用
startActivityForResult时,AS会提示你该方法已被弃用,点进去看会告诉你应该使用
registerForActivityResult方法替代。没错,这就是
androidx给我们提供的
ActivityResult功能,并且这个功能不仅支持
ActivityResult回调,还支持打开文档,拍摄照片,选择文件等各种各样的回调,同样也包括我们今天要说的权限申请
其实Android在官方文档 请求运行时权限 中就已经将其作为动态权限申请的推荐方法了,如下示例代码所示:
val requestPermissionLauncher = registerForActivityResult(RequestPermission() ) { isGranted: Boolean -> if (isGranted) { // Permission is granted. Continue the action or workflow in your // app. } else { // Explain to the user that the feature is unavailable because the // feature requires a permission that the user has denied. At the // same time, respect the user's decision. Don't link to system // settings in an effort to convince the user to change their // decision. } } when { ContextCompat.checkSelfPermission( CONTEXT, Manifest.permission.REQUESTED_PERMISSION ) == PackageManager.PERMISSION_GRANTED -> { // You can use the API that requires the permission. } shouldShowRequestPermissionRationale(...) -> { // In an educational UI, explain to the user why your app requires this // permission for a specific feature to behave as expected, and what // features are disabled if it's declined. In this UI, include a // "cancel" or "no thanks" button that lets the user continue // using your app without granting the permission. showInContextUI(...) } else -> { // You can directly ask for the permission. // The registered ActivityResultCallback gets the result of this request. requestPermissionLauncher.launch( Manifest.permission.REQUESTED_PERMISSION) } }
如果你遵照以上方法这么写的话,在实际调用的时候会直接发生崩溃:
java.lang.IllegalStateException: LifecycleOwner Activity is attempting to register while current state is RESUMED. LifecycleOwners must call register before they are STARTED.
这段报错很明显的告诉我们,我们的注册工作必须要在
Activity声明周期
STARTED之前进行(也就是
onCreate时和
onStart完成前),但这样我们就必须要事先注册好所有可能会用到的权限,没办法做到随时随地有需要时再申请权限了,有办法解决这个问题吗?答案是肯定的。
绕过生命周期检测
想解决这个问题,我们必须要知道问题的成因,让我们带着问题进到源码中一探究竟:
public final <I, O> ActivityResultLauncher<I> registerForActivityResult( @NonNull ActivityResultContract<I, O> contract, @NonNull ActivityResultCallback<O> callback) { return registerForActivityResult(contract, mActivityResultRegistry, callback); } public final <I, O> ActivityResultLauncher<I> registerForActivityResult( @NonNull final ActivityResultContract<I, O> contract, @NonNull final ActivityResultRegistry registry, @NonNull final ActivityResultCallback<O> callback) { return registry.register( "activity_rq#" + mNextLocalRequestCode.getAndIncrement(), this, contract, callback); } public final <I, O> ActivityResultLauncher<I> register( @NonNull final String key, @NonNull final LifecycleOwner lifecycleOwner, @NonNull final ActivityResultContract<I, O> contract, @NonNull final ActivityResultCallback<O> callback) { Lifecycle lifecycle = lifecycleOwner.getLifecycle(); if (lifecycle.getCurrentState().isAtLeast(Lifecycle.State.STARTED)) { throw new IllegalStateException("LifecycleOwner " + lifecycleOwner + " is " + "attempting to register while current state is " + lifecycle.getCurrentState() + ". LifecycleOwners must call register before " + "they are STARTED."); } registerKey(key); LifecycleContainer lifecycleContainer = mKeyToLifecycleContainers.get(key); if (lifecycleContainer == null) { lifecycleContainer = new LifecycleContainer(lifecycle); } LifecycleEventObserver observer = new LifecycleEventObserver() { ... }; lifecycleContainer.addObserver(observer); mKeyToLifecycleContainers.put(key, lifecycleContainer); return new ActivityResultLauncher<I>() { ... }; }
我们可以发现,
registerForActivityResult实际上就是调用了
ComponentActivity内部成员变量的
mActivityResultRegistry.register方法,而在这个方法的一开头就检查了当前
Activity的生命周期,如果生命周期位于
STARTED后则直接抛出异常,那我们该如何绕过这个限制呢?
其实在
register方法的下面就有一个同名重载方法,这个方法并没有做生命周期的检测:
public final <I, O> ActivityResultLauncher<I> register( @NonNull final String key, @NonNull final ActivityResultContract<I, O> contract, @NonNull final ActivityResultCallback<O> callback) { registerKey(key); mKeyToCallback.put(key, new CallbackAndContract<>(callback, contract)); if (mParsedPendingResults.containsKey(key)) { @SuppressWarnings("unchecked") final O parsedPendingResult = (O) mParsedPendingResults.get(key); mParsedPendingResults.remove(key); callback.onActivityResult(parsedPendingResult); } final ActivityResult pendingResult = mPendingResults.getParcelable(key); if (pendingResult != null) { mPendingResults.remove(key); callback.onActivityResult(contract.parseResult( pendingResult.getResultCode(), pendingResult.getData())); } return new ActivityResultLauncher<I>() { ... }; }
找到这个方法就简单了,我们将
registerForActivityResult方法调用替换成
activityResultRegistry.register调用就可以了
当然,我们还需要注意一些小细节,检查生命周期的
register方法同时也会注册生命周期回调,当
Activity被销毁时会将我们注册的
ActivityResult回调移除,我们也需要给我们封装的方法加上这个逻辑,最终实现就如下所示。
最终实现
private val nextLocalRequestCode = AtomicInteger() private val nextKey: String get() = "activity_rq#${nextLocalRequestCode.getAndIncrement()}" fun ComponentActivity.requestPermission( permission: String, onPermit: () -> Unit, onDeny: (shouldShowCustomRequest: Boolean) -> Unit ) { if (ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED) { onPermit() return } var launcher by Delegates.notNull<ActivityResultLauncher<String>>() launcher = activityResultRegistry.register( nextKey, ActivityResultContracts.RequestPermission() ) { result -> if (result) { onPermit() } else { onDeny(!ActivityCompat.shouldShowRequestPermissionRationale(this, permission)) } launcher.unregister() } lifecycle.addObserver(object : LifecycleEventObserver { override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) { if (event == Lifecycle.Event.ON_DESTROY) { launcher.unregister() lifecycle.removeObserver(this) } } }) launcher.launch(permission) } fun ComponentActivity.requestPermissions( permissions: Array<String>, onPermit: () -> Unit, onDeny: (shouldShowCustomRequest: Boolean) -> Unit ) { var hasPermissions = true for (permission in permissions) { if (ContextCompat.checkSelfPermission( this, permission ) != PackageManager.PERMISSION_GRANTED ) { hasPermissions = false break } } if (hasPermissions) { onPermit() return } var launcher by Delegates.notNull<ActivityResultLauncher<Array<String>>>() launcher = activityResultRegistry.register( nextKey, ActivityResultContracts.RequestMultiplePermissions() ) { result -> var allAllow = true for (allow in result.values) { if (!allow) { allAllow = false break } } if (allAllow) { onPermit() } else { var shouldShowCustomRequest = false for (permission in permissions) { if (!ActivityCompat.shouldShowRequestPermissionRationale(this, permission)) { shouldShowCustomRequest = true break } } onDeny(shouldShowCustomRequest) } launcher.unregister() } lifecycle.addObserver(object : LifecycleEventObserver { override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) { if (event == Lifecycle.Event.ON_DESTROY) { launcher.unregister() lifecycle.removeObserver(this) } } }) launcher.launch(permissions) }