一个类快速实现 Android 6.0 运行时权限适配

前言

现在来谈 Android 6.0 运行时权限适配，可以说是很过时了，可是为什么还要写呢？一是试用了目前 GitHub 上排名比较靠前的开源项目，确实都很棒，但是在易用性还是难以令人满意，便萌生了自己撸一个的想法。二是看了下目前国内主流的应用，发现很多都还没有适配 Android 6.0 ，因此觉得这篇文章还有它的意义。

使用

既然上面说到了易用性，那我们先来看看使用方法在需要申请权限的地方调用

PermissionReq.with(this) // Activity or Fragment
        .permissions(Manifest.permission.CAMERA,
                Manifest.permission.WRITE_EXTERNAL_STORAGE) // 需要申请的权限
        .result(new PermissionReq.Result() { // 申请结果回调
            @Override
            public void onGranted() { // 申请成功
                // do something
            }
            @Override
            public void onDenied() { // 申请失败
                // do something
            }
        })
        .request();
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在 Activity 基类和 Fragment 基类中添加以下代码

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    PermissionReq.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
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API 设计采用了比较流行的流式调用，不知道大家看了是什么感觉，我觉得使用起来比较简单，而且不会破坏原来的代码结构。说到这里，我多说一句，现在有很多开源框架都是使用注解的方式来回调申请结果的，我觉得用这种方式虽然代码层次变少了，但是可读性变差了，而且可能会破坏原来代码结构。

这里还有个亮点不知道大家注意到没，我们没有用到 RequestCode ，那 RequestCode 哪里去了呢，在接下来的内容中我会告诉大家。这也是我最喜欢的地方，不需要在每个申请权限的地方定义一个 RequestCode ，更不用担心 RequestCode 会重复，因为 PermissionReq 已经帮大家处理好了。

源码解析

看完使用方式后我们来看下内部实现，我们按照流程来看

首先我们要检查 App 注册了哪些权限，如果要申请的权限压根就没有在 Manifest 中注册，那么肯定会失败的

initManifestPermission(activity);
for (String permission : mPermissions) {
    if (!sManifestPermissionSet.contains(permission)) {
        if (mResult != null) {
            mResult.onDenied();
        }
        return;
    }
}

private static Set<String> sManifestPermissionSet;
private static synchronized void initManifestPermission(Context context) {
    if (sManifestPermissionSet == null) {
        sManifestPermissionSet = new HashSet<>();
        try {
            PackageInfo packageInfo = context.getPackageManager().getPackageInfo(context.getPackageName(), PackageManager.GET_PERMISSIONS);
            String[] permissions = packageInfo.requestedPermissions;
            Collections.addAll(sManifestPermissionSet, permissions);
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
    }
}
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为了线程安全我们添加了 synchronized 修饰符。

如果要申请的权限已经在 Manifest 中注册了，我们接下来就要区分下系统版本了，如果系统版本低于 26 直接返回成功，否则才需要申请权限这段代码比较简单，我就不贴了

如果系统版本 >= 26 ，那么才开始我们真正的申请流程检查要申请的权限是否已经被允许，如果已经被允许，那么就没必要再申请了

List<String> deniedPermissionList = getDeniedPermissions(activity, mPermissions);
if (deniedPermissionList.isEmpty()) {
    if (mResult != null) {
        mResult.onGranted();
    }
    return;
}

private static List<String> getDeniedPermissions(Context context, String[] permissions) {
    List<String> deniedPermissionList = new ArrayList<>();
    for (String permission : permissions) {
        if (ContextCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
            deniedPermissionList.add(permission);
        }
    }
    return deniedPermissionList;
}
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如果要申请的权限没有全部被允许，那么我们就需要向系统发送申请了生成 RequestCode

int requestCode = genRequestCode();

private static AtomicInteger sRequestCode = new AtomicInteger(0);
private static int genRequestCode() {
    return sRequestCode.incrementAndGet();
}
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还记得上面说我们在使用时不需要定义 RequestCode 吗，至此，RequestCode 终于浮出水面我们在内部使用一个静态自增的 AtomicInteger 作为 RequestCode ，保证 RequestCode 不会重复，使用 AtomicInteger 而不直接使用 int 是为了线程安全

向系统发送申请

String[] deniedPermissions = deniedPermissionList.toArray(new String[deniedPermissionList.size()]);
requestPermissions(mObject, deniedPermissions, requestCode);
sResultArray.put(requestCode, mResult);

@TargetApi(Build.VERSION_CODES.M)
private static void requestPermissions(Object object, String[] permissions, int requestCode) {
    if (object instanceof Activity) {
        ((Activity) object).requestPermissions(permissions, requestCode);
    } else if (object instanceof Fragment) {
        ((Fragment) object).requestPermissions(permissions, requestCode);
    }
}
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申请时区分来源，申请后把 Result 放入 Array 中保存起来，等待申请结果到达

申请结果到达后通知申请者

public static void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    Result result = sResultArray.get(requestCode);
    if (result == null) {
        return;
    }
    sResultArray.remove(requestCode);
    for (int grantResult : grantResults) {
        if (grantResult != PackageManager.PERMISSION_GRANTED) {
            result.onDenied();
            return;
        }
    }
    result.onGranted();
}
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到这里我们的申请权限流程已经走完了，源码也看完了。

完整代码

为了方便大家使用，我贴一下完整代码

public class PermissionReq {
    private static AtomicInteger sRequestCode = new AtomicInteger(0);
    private static SparseArray<Result> sResultArray = new SparseArray<>();
    private static Set<String> sManifestPermissionSet;

    public interface Result {
        void onGranted();

        void onDenied();
    }

    private Object mObject;
    private String[] mPermissions;
    private Result mResult;

    private PermissionReq(Object object) {
        mObject = object;
    }

    public static PermissionReq with(@NonNull Activity activity) {
        return new PermissionReq(activity);
    }

    public static PermissionReq with(@NonNull Fragment fragment) {
        return new PermissionReq(fragment);
    }

    public PermissionReq permissions(@NonNull String... permissions) {
        mPermissions = permissions;
        return this;
    }

    public PermissionReq result(@Nullable Result result) {
        mResult = result;
        return this;
    }

    public void request() {
        Activity activity = getActivity(mObject);
        if (activity == null) {
            throw new IllegalArgumentException(mObject.getClass().getName() + " is not supported");
        }

        initManifestPermission(activity);
        for (String permission : mPermissions) {
            if (!sManifestPermissionSet.contains(permission)) {
                if (mResult != null) {
                    mResult.onDenied();
                }
                return;
            }
        }

        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            if (mResult != null) {
                mResult.onGranted();
            }
            return;
        }

        List<String> deniedPermissionList = getDeniedPermissions(activity, mPermissions);
        if (deniedPermissionList.isEmpty()) {
            if (mResult != null) {
                mResult.onGranted();
            }
            return;
        }

        int requestCode = genRequestCode();
        String[] deniedPermissions = deniedPermissionList.toArray(new String[deniedPermissionList.size()]);
        requestPermissions(mObject, deniedPermissions, requestCode);
        sResultArray.put(requestCode, mResult);
    }

    public static void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        Result result = sResultArray.get(requestCode);

        if (result == null) {
            return;
        }

        sResultArray.remove(requestCode);

        for (int grantResult : grantResults) {
            if (grantResult != PackageManager.PERMISSION_GRANTED) {
                result.onDenied();
                return;
            }
        }
        result.onGranted();
    }

    @TargetApi(Build.VERSION_CODES.M)
    private static void requestPermissions(Object object, String[] permissions, int requestCode) {
        if (object instanceof Activity) {
            ((Activity) object).requestPermissions(permissions, requestCode);
        } else if (object instanceof Fragment) {
            ((Fragment) object).requestPermissions(permissions, requestCode);
        }
    }

    private static List<String> getDeniedPermissions(Context context, String[] permissions) {
        List<String> deniedPermissionList = new ArrayList<>();
        for (String permission : permissions) {
            if (ContextCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                deniedPermissionList.add(permission);
            }
        }
        return deniedPermissionList;
    }

    private static synchronized void initManifestPermission(Context context) {
        if (sManifestPermissionSet == null) {
            sManifestPermissionSet = new HashSet<>();
            try {
                PackageInfo packageInfo = context.getPackageManager().getPackageInfo(context.getPackageName(), PackageManager.GET_PERMISSIONS);
                String[] permissions = packageInfo.requestedPermissions;
                Collections.addAll(sManifestPermissionSet, permissions);
            } catch (PackageManager.NameNotFoundException e) {
                e.printStackTrace();
            }
        }
    }

    private static Activity getActivity(Object object) {
        if (object != null) {
            if (object instanceof Activity) {
                return (Activity) object;
            } else if (object instanceof Fragment) {
                return ((Fragment) object).getActivity();
            }
        }
        return null;
    }

    private static int genRequestCode() {
        return sRequestCode.incrementAndGet();
    }
}
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