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RxPermissions 源码解析

简介

RxPermissions 是基于 RxJava 开发的用于帮助在Android 6.0 中处理运行时权限检测的框架。在 Android 6.0 中增加了对危险权限的动态申请，而不是像 Android 6.0 之前的默认全部获取的方式。

原始动态权限的获取

如果按照以往的获取权限方式的话，那么我们获取权限一般需要有 3 个步骤，第一步是先判断当前是否已经获取到该权限了；第 2 步申请对应的权限；第 3 步在 Activity 或者 Fragment 中处理获取权限的结果。具体的实现步骤如下：

step 1：判断权限是否已经获取。

if (ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.CAMERA)) {//用于开发者提示用户权限的用途} else {//申请权限}
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step 2:申请权限

ActivityCompat.requestPermissions(MainActivity.this,new String[]{Manifest.permission.CAMERA},REQUEST_CAMERA);
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step 3:结果处理

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,@NonNull int[] grantResults) {// 判断请求码，确定当前申请的权限if (requestCode == REQUEST_CAMERA) {//判断权限是否申请通过if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {//授权成功} else {//授权失败}} else {super.onRequestPermissionsResult(requestCode, permissions, grantResults);}
}复制代码

RxPermissions 的简单使用

其实 RxPermissions 的使用方式有两种

方式 1：

RxPermissions rxPermissions = new RxPermissions(MainActivity.this);rxPermissions.request(Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE)//这里填写所需要的权限.subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Exception {if (aBoolean) {// 通过}else{// 拒绝}}});
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方式 2：结合 RxBinding 来使用

RxPermissions rxPermissions = new RxPermissions(MainActivity.this);
// Must be done during an initialization phase like onCreate
RxView.clicks(findViewById(R.id.enableCamera)).compose(rxPermissions.ensure(Manifest.permission.CAMERA)).subscribe(granted -> {// R.id.enableCamera has been clicked});复制代码

源码分析

整体介绍

接着我们来对这个 RxPermissions 进行一个源码的解析，但是打开源码的时候，我们可以发现，这个库里面，其实就只有 3 个类：RxPermissions、RxPermissionsFragment、Permission

RxPermissions
- 最主要的实现类，利用 rxjava，为我们提供了方便权限申请的类
RxPermissionsFragment
- 是一个 fragment，主要的动态权限获取类
Permission
- 定义的权限的 model 类

源码分析

RxPermissions 实例创建

对于源码的分析，我们应该先从简单的使用入手。下面我们可以先看看实例化 RxPermissionsFragment 的时候是做了什么？

    RxPermissionsFragment mRxPermissionsFragment;public RxPermissions(@NonNull Activity activity) {mRxPermissionsFragment = getRxPermissionsFragment(activity);}复制代码

我们可以看到，上面的代码中，实例化 RxPermissionsFragment 的时候，里面先创建了一个 RxPermissionsFragment 的实例。我们再接着看 getRxPermissionsFragment 这个方法的实现。

    private RxPermissionsFragment getRxPermissionsFragment(Activity activity) {//  查找 RxPermissionsFragment 是否已经被添加了RxPermissionsFragment rxPermissionsFragment = findRxPermissionsFragment(activity);boolean isNewInstance = rxPermissionsFragment == null;if (isNewInstance) {rxPermissionsFragment = new RxPermissionsFragment();FragmentManager fragmentManager = activity.getFragmentManager();fragmentManager.beginTransaction().add(rxPermissionsFragment, TAG).commitAllowingStateLoss();fragmentManager.executePendingTransactions();}return rxPermissionsFragment;}复制代码

在 getRxPermissionsFragment() 这个方法中，首先是先查找当前是否已经添加了这个 rxPermissionsFragment 的实例，如果已经添加，那么直接返回已经添加的实例，如果没有添加过的话，那么就重新再创建一个 RxPermissionsFragment 实例并提交；

    private RxPermissionsFragment findRxPermissionsFragment(Activity activity) {return (RxPermissionsFragment) activity.getFragmentManager().findFragmentByTag(TAG);}
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到此，rxPermissionsFragment 的实例化已经完成，接着我们需要看看 request 这个方法中实现了什么。

request 方法

    public Observable<Boolean> request(final String... permissions) {return Observable.just(TRIGGER).compose(ensure(permissions));}
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    static final Object TRIGGER = new Object();
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从上面的代码中，我们可以看到，request 方法中需要传入的参数是一个权限的数组，返回值是 Observable 对象。Observable.just(TRIGGER) 是快捷创建一个 Observable 的方式，由于 TRIGGER 是一个空的 Object 对象，所以 TRIGGER 就是一个占位符而已，Observable.just(TRIGGER) 创建的是一个 Observable,之后通过 compose 将 Observable 转化为 Observable 并返回。在 compose 中需要的参数是一个 ObservableTransformer，那么我们接着看 ensure() 这个方法。

ensure(permissions);

public <T> ObservableTransformer<T, Boolean> ensure(final String... permissions) {// 创建一个Transformer对象返回return new ObservableTransformer<T, Boolean>() {@Overridepublic ObservableSource<Boolean> apply(Observable<T> o) {//request(o, permissions) 方法返回 Observable<Permission> 对象return request(o, permissions)// 将 Observable<Permission> 转换为 Observable<Boolean>，在这里会等待所有的权限都返回了一次性发射数据。.buffer(permissions.length).flatMap(new Function<List<Permission>, ObservableSource<Boolean>>() {@Overridepublic ObservableSource<Boolean> apply(List<Permission> permissions) throws Exception {// 如果permissions为空那么直接返回Observable.empty();if (permissions.isEmpty()) {// Occurs during orientation change, when the subject receives onComplete.// In that case we don't want to propagate that empty list to the// subscriber, only the onComplete.return Observable.empty();}// Return true if all permissions are granted.for (Permission p : permissions) {if (!p.granted) {return Observable.just(false);}}return Observable.just(true);}});}};}复制代码

在 ensure 的这个方法中，最终会返回的是 ObservableTransformer<T, Boolean> 对象。接着我们看看 ObservableTransformer 的匿名实现类里面的 apply 方法，这里实现的就是将 Observable 转换为 Observable 的操作。我们对 apply 这个方法里面的代码进行简化一下。

return request(o,permissions).buffer(permissions.length).flatMap(new Function<List<Permission>, ObservableSource<Boolean>>{});
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request() 方法返回 Observable 对象
buffer(len) 操作符将一个 Observable 变换为 Observable<List>，原来的 Observable 正常发射数据，变换产生的 Observable 发射这些数据的缓存集合。buffer 将数据缓存到一个集合当中，然后在适当(比如：所有请求的权限结果都返回了）的时机一起发送。
flatMap() 方法将 Observable<List> 转化为 Observable

request(o, permissions);

    private Observable<Permission> request(final Observable<?> trigger, final String... permissions) {if (permissions == null || permissions.length == 0) {throw new IllegalArgumentException("RxPermissions.request/requestEach requires at least one input permission");}return oneOf(trigger, pending(permissions)).flatMap(new Function<Object, Observable<Permission>>() {@Overridepublic Observable<Permission> apply(Object o) throws Exception {return requestImplementation(permissions);}});}复制代码

在 request 这个方法里面，其实 oneOf() 和 pending() 方法我们可以忽略的，主要的话，我们应该关注 requestImplementation(final String... permissions) 这个方法，在这个方法里面，主要实现了权限的请求。

requestImplementation

@TargetApi(Build.VERSION_CODES.M)private Observable<Permission> requestImplementation(final String... permissions) {List<Observable<Permission>> list = new ArrayList<>(permissions.length);List<String> unrequestedPermissions = new ArrayList<>();// In case of multiple permissions, we create an Observable for each of them.// At the end, the observables are combined to have a unique response.for (String permission : permissions) {mRxPermissionsFragment.log("Requesting permission " + permission);if (isGranted(permission)) {// Already granted, or not Android M// Return a granted Permission object.// 权限已经被同意或者不是 Android 6.0 以上版本，创建一个 同意的 Permission 对象。list.add(Observable.just(new Permission(permission, true, false)));continue;}if (isRevoked(permission)) {// 权限被拒绝，返回一个 拒绝的 Permission 对象。list.add(Observable.just(new Permission(permission, false, false)));continue;}PublishSubject<Permission> subject = mRxPermissionsFragment.getSubjectByPermission(permission);// 如果 subject 不存在，那么创建一个 subject。if (subject == null) {unrequestedPermissions.add(permission);subject = PublishSubject.create();mRxPermissionsFragment.setSubjectForPermission(permission, subject);}list.add(subject);}// 还未提起申请的权限进行申请if (!unrequestedPermissions.isEmpty()) {String[] unrequestedPermissionsArray = unrequestedPermissions.toArray(new String[unrequestedPermissions.size()]);requestPermissionsFromFragment(unrequestedPermissionsArray);}// 严格按照顺序发射数据return Observable.concat(Observable.fromIterable(list));}复制代码

onRequestPermissionsResult()

@TargetApi(Build.VERSION_CODES.M)public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[], @NonNull int[] grantResults) {super.onRequestPermissionsResult(requestCode, permissions, grantResults);if (requestCode != PERMISSIONS_REQUEST_CODE) return;boolean[] shouldShowRequestPermissionRationale = new boolean[permissions.length];for (int i = 0; i < permissions.length; i++) {shouldShowRequestPermissionRationale[i] = shouldShowRequestPermissionRationale(permissions[i]);}onRequestPermissionsResult(permissions, grantResults, shouldShowRequestPermissionRationale);}void onRequestPermissionsResult(String permissions[], int[] grantResults, boolean[] shouldShowRequestPermissionRationale) {for (int i = 0, size = permissions.length; i < size; i++) {log("onRequestPermissionsResult  " + permissions[i]);// Find the corresponding subjectPublishSubject<Permission> subject = mSubjects.get(permissions[i]);if (subject == null) {// No subject foundLog.e(RxPermissions.TAG, "RxPermissions.onRequestPermissionsResult invoked but didn't find the corresponding permission request.");return;}// 发射权限申请结果mSubjects.remove(permissions[i]);boolean granted = grantResults[i] == PackageManager.PERMISSION_GRANTED;subject.onNext(new Permission(permissions[i], granted, shouldShowRequestPermissionRationale[i]));subject.onComplete();}}复制代码

RxJava 操作符

Observable.just()

just 操作符是将一个对象转化为 Observable 的操作符。这个对象可以是一个数字、字符串或者是数组对象等，是 RxJava 中快速创建一个 Observable 对象的操作符。如果有 subscriber 订阅的话，那么会依次调用 onNext() 和 OnComplete() 方法。所以这里只是创建了一个 Observable 对象，方便后续的调用。

compose(Transformer)操作符

compose 操作符是对 Observable 对象的整体转化。例如：通过 Transformer，我们可以将 Observable 对象转换成 Observable 对象了。

    public static ObservableTransformer<String,Boolean> getTransformer(){return new ObservableTransformer<String, Boolean>() {@Overridepublic ObservableSource<Boolean> apply(Observable<String> upstream) {return upstream.flatMap(new Function<String, ObservableSource<Boolean>>() {@Overridepublic ObservableSource<Boolean> apply(String s) throws Exception {return Observable.just(true);}});}};}
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/*** 线程切换* @return*/public static <T> ObservableTransformer<T,T> getScheduler(){return new ObservableTransformer<T, T>() {@Overridepublic ObservableSource<T> apply(Observable<T> upstream) {return upstream.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());}};}复制代码

buffer 操作符

buffer 操作符将一个 Observable 变换为另一个，原来的 Observable 正常发射数据，变换产生的 Observable 发射这些数据的缓存集合。buffer将数据缓存到一个集合当中，然后在适当的时机一起发送。 buffer(count) 以列表(List)的形式发射非重叠的缓存，每一个缓存至多包含来自原始Observable的count项数据（最后发射的列表数据可能少于count项）

例如：缓存 2 个数据之后，再发送数据（调用 buffer(count) 函数）

                Observable.just(1,2,3,4,5,6).buffer(2).subscribe(integers -> {Log.i(TAG, "accept size: "+integers.size());for (Integer integer : integers) {Log.i(TAG, "accept: "+integer);}});
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输出结果

2018-12-14 11:16:28.452 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept size: 2
2018-12-14 11:16:28.452 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 1
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 2
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept size: 2
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 3
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 4
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept size: 2
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 5
2018-12-14 11:16:28.453 28126-28126/com.luwei.lwbaselib I/LwBaseActivity: accept: 6
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例如：缓存 3 个数据，再发送数据，每次移动 1 步

                Observable.just(1,2,3,4).buffer(3,1).subscribe(integers -> {Log.i(TAG, "accept size: "+integers.size());for (Integer integer : integers) {Log.i(TAG, "accept: "+integer);}});
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输出结果

2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept size: 3
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 1
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 2
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 3
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept size: 3
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 2
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 3
2018-12-14 11:24:31.455 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 4
2018-12-14 11:24:31.456 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept size: 2
2018-12-14 11:24:31.456 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 3
2018-12-14 11:24:31.456 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 4
2018-12-14 11:24:31.456 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept size: 1
2018-12-14 11:24:31.456 29164-29164/com.luwei.lwbaselib I/LwBaseActivity: accept: 4
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concat 操作符

是接收若干个Observables，发射数据是有序的，不会交叉。

Subject

作为 Observable 和 Observer 之间的桥梁
可以当做 Observable
可以当做 Observer

PublishSubject

继承至 Subject，它的 Observer 只会接收到 PublishSubject 被订阅之后发送的数据。示例代码如下；我们只会接收到 publishSubject3 和 publishSubject4；

                PublishSubject<String> publishSubject = PublishSubject.create();publishSubject.onNext("publishSubject1");publishSubject.onNext("publishSubject2");publishSubject.subscribe(new Consumer<String>() {@Overridepublic void accept(String s) throws Exception {Log.i(TAG, "accept: "+s);}});publishSubject.onNext("publishSubject3");publishSubject.onNext("publishSubject4");复制代码

执行结果

2018-12-14 11:33:18.168 29916-29916/com.luwei.lwbaselib I/LwBaseActivity: accept: publishSubject3
2018-12-14 11:33:18.168 29916-29916/com.luwei.lwbaselib I/LwBaseActivity: accept: publishSubject4
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举一反三

可以看到，在 RxPermissions 这个获取权限的开源框架中，往 Activity 中添加了一个空的 Fragment，这个 fragment 才是用来发起申请权限和处理权限的请求，最后再将结果返回，这样子就避免了我们发送请求之后，还需要在 onRequestPermissionsResult 中进行处理，并判断 requestCode 等繁琐操作。想到这里，我们平时使用 startActivityForResult 时，我们也可以同样采用这样的思路来简化我们的请求。

同样的，我们采用添加空白的 fragment，来做 startActivityForResult 请求，主要的实现类有 SimpleForResult 和 SimpleOnResultFragment，ActivityResultInfo 是请求 model，接下我们先看代码。

SimpleForResult


/*** @Author: chenjianrun* @Time: 2018/12/7* @Description:   避免调用 startActivity 时，需要 onActivityResult 处理的类*/
public class SimpleForResult {private static final String TAG = "SimpleForResult";private SimpleOnResultFragment mSimpleOnResultFragment;public SimpleForResult(AppCompatActivity activity) {mSimpleOnResultFragment = getOnResultFragment(activity.getSupportFragmentManager());}public SimpleForResult(Fragment fragment){mSimpleOnResultFragment = getOnResultFragment(fragment.getChildFragmentManager());}private SimpleOnResultFragment getOnResultFragment(FragmentManager fragmentManager) {SimpleOnResultFragment simpleOnResultFragment = findSimpleOnResultFragment(fragmentManager);if (simpleOnResultFragment == null) {simpleOnResultFragment = new SimpleOnResultFragment();fragmentManager.beginTransaction().add(simpleOnResultFragment, TAG).commitAllowingStateLoss();fragmentManager.executePendingTransactions();}return simpleOnResultFragment;}private SimpleOnResultFragment findSimpleOnResultFragment(FragmentManager fragmentManager) {return (SimpleOnResultFragment) fragmentManager.findFragmentByTag(TAG);}public Observable<ActivityResultInfo> startForResult(Intent intent) {return mSimpleOnResultFragment.startForResult(intent);}public Observable<ActivityResultInfo> startForResult(Class<?> clazz) {Intent intent = new Intent(mSimpleOnResultFragment.getActivity(), clazz);return startForResult(intent);}public void startForResult(Intent intent, Callback callback) {mSimpleOnResultFragment.startForResult(intent, callback);}public void startForResult(Class<?> clazz, Callback callback) {Intent intent = new Intent(mSimpleOnResultFragment.getActivity(), clazz);startForResult(intent, callback);}public interface Callback {void onActivityResult(int requestCode, int resultCode, Intent data);}
}复制代码

SimpleOnResultFragment


/*** @Author: chenjianrun* @Time: 2018/12/7* @Description:    真正调用 startActivity 和处理 onActivityResult 的类。*/
public class SimpleOnResultFragment extends Fragment {private static Map<Integer, PublishSubject<ActivityResultInfo>> mSubjects = new HashMap<>();private static Map<Integer, SimpleForResult.Callback> mCallbacks = new HashMap<>();public SimpleOnResultFragment() {}@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setRetainInstance(true);}public Observable<ActivityResultInfo> startForResult(final Intent intent) {int requestCode = generateRequestCode();PublishSubject<ActivityResultInfo> subject = PublishSubject.create();mSubjects.put(requestCode, subject);startActivityForResult(intent, requestCode);return subject;}public void startForResult(Intent intent, SimpleForResult.Callback callback) {int requestCode = generateRequestCode();mCallbacks.put(requestCode, callback);startActivityForResult(intent, requestCode);}@Overridepublic void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);//rxjava方式的处理PublishSubject<ActivityResultInfo> subject = mSubjects.remove(requestCode);if (subject != null) {subject.onNext(new ActivityResultInfo(requestCode, resultCode, data));subject.onComplete();}//callback方式的处理SimpleForResult.Callback callback = mCallbacks.remove(requestCode);if (callback != null) {callback.onActivityResult(requestCode, resultCode, data);}}private int generateRequestCode(){Random random = new Random();for (;;){int code = random.nextInt(65536);if (!mSubjects.containsKey(code) && !mCallbacks.containsKey(code)){return code;}}}
}
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ActivityResultInfo

package com.luwei.util.forresult;import android.content.Intent;/*** @Author: chenjianrun* @Time: 2018/12/7* @Description:*/
public class ActivityResultInfo {private int requestCode;private int resultCode;private Intent data;public ActivityResultInfo(int requestCode, int resultCode, Intent data) {this.requestCode = requestCode;this.resultCode = resultCode;this.data = data;}public int getRequestCode() {return requestCode;}public void setRequestCode(int requestCode) {this.requestCode = requestCode;}public ActivityResultInfo(int resultCode, Intent data) {this.resultCode = resultCode;this.data = data;}public int getResultCode() {return resultCode;}public void setResultCode(int resultCode) {this.resultCode = resultCode;}public Intent getData() {return data;}public void setData(Intent data) {this.data = data;}
}复制代码

简单使用示例

简单的 Activity 调用

// 简化调用 startActivityForResult 及避免在 onActivityResult 中处理繁琐的结果SimpleForResult simpleForResult = new SimpleForResult(this);simpleForResult.startForResult(ToastActivity.class).subscribe((resultInfo) -> {if (resultInfo.getData() != null) {ToastUtils.showLong(resultInfo.getData().getStringExtra("result"));}});
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调用摄像头

    /*** 打开摄像头*/private void openCamera() {try {mTmpFile = FileUtils.createTmpFile(this);} catch (IOException e) {e.printStackTrace();}simpleForResult.startForResult(getOpenCameraIntent(this, mTmpFile)).subscribe((resultInfo -> {if (resultInfo.getResultCode() == RESULT_OK) {mHeadUrl = mTmpFile.getAbsolutePath();ImageLoaderUtils.loadCircleImage(this, ivHeader, mHeadUrl);// 裁剪(如果没有要求可裁剪，也可以不要）startPictureZoom(mTmpFile);}}));}/*** 获取打开照相机的 intent，适配 Android 7.0* @param activity* @param mTmpFile* @return*/public static Intent getOpenCameraIntent(Activity activity,File mTmpFile){Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);if (intent.resolveActivity(activity.getPackageManager()) != null) {if (mTmpFile != null && mTmpFile.exists()) {if (Build.VERSION.SDK_INT >= 24) {// 适配 Android 7.0intent.putExtra(MediaStore.EXTRA_OUTPUT,FileProvider.getUriForFile(activity, activity.getPackageName()+".provider",mTmpFile));} else {intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(mTmpFile));}} else {Toast.makeText(activity, me.nereo.image_selector.R.string.error_image_not_exist, Toast.LENGTH_SHORT).show();}} else {Toast.makeText(activity, me.nereo.image_selector.R.string.msg_no_camera, Toast.LENGTH_SHORT).show();}return intent;}复制代码