Android动态权限申请功能怎么实现寻技术

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)
}

本文地址：https://www.xunjs.com/android/view_17735.html

Tags：请功申请动态 Android 权限功能

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