前言

权限是绝大多数App必不可少的部分，不管你仍在用原生的方式，还是其他的开源库，AndPermission绝对是值得学习的一个开源库，今天，我们就来学习下它的设计思想。

AndPermission

思路

权限库的思路大体上都如下图所示，也玩不出太复杂的花样。

使用

1.添加引用 implementation 'com.yanzhenjie.permission2.0.1'

2.请求权限

AndPermission.with(this)

        .runtime()
        .permission(permissions)
        .rationale(new RuntimeRationale())
        .onGranted(new Action<List<String>>() {
            @Override
            public void onAction(List<String> permissions) {
                toast(R.string.successfully);
            }
        })
        .onDenied(new Action<List<String>>() {
            @Override
            public void onAction(@NonNull List<String> permissions) {
                toast(R.string.failure);
                if (AndPermission.hasAlwaysDeniedPermission(MainActivity.this, permissions)) {
                    showSettingDialog(MainActivity.this, permissions);
                }
            }
        })
        .start();

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3.安装应用

private void installPackage() {

    AndPermission.with(this)
        .install()
        .file(new File(Environment.getExternalStorageDirectory(), "android.apk"))
        .rationale(new InstallRationale())
        .onGranted(new Action<File>() {
            @Override
            public void onAction(File data) {
                // Installing.
                toast(R.string.successfully);
            }
        })
        .onDenied(new Action<File>() {
            @Override
            public void onAction(File data) {
                // The user refused to install.
                toast(R.string.failure);
            }
        })
        .start();
}

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4.应用上显示（悬浮窗）

private void requestPermissionForAlertWindow() {

    AndPermission.with(this).overlay().rationale(new OverlayRationale()).onGranted(new Action<Void>() {
        @Override
        public void onAction(Void data) {
            toast(R.string.successfully);
            showAlertWindow();
        }
    }).onDenied(new Action<Void>() {
        @Override
        public void onAction(Void data) {
            toast(R.string.failure);
        }
    }).start();
}

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5.修改系统设置

private void requestWriteSystemSetting() {

    AndPermission.with(this).setting().write().rationale(new WriteSettingRationale()).onGranted(new Action<Void>() {
        @Override
        public void onAction(Void data) {
            toast(R.string.successfully);
        }
    }).onDenied(new Action<Void>() {
        @Override
        public void onAction(Void data) {
            toast(R.string.failure);
        }
    }).start();
}

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6.通知

private void requestNotificationListener() {

    AndPermission.with(this)
        .notification()
        .listener()
        .rationale(new NotifyListenerRationale())
        .onGranted(new Action<Void>() {
            @Override
            public void onAction(Void data) {
                toast(R.string.successfully);
            }
        })
        .onDenied(new Action<Void>() {
            @Override
            public void onAction(Void data) {
                toast(R.string.failure);
            }
        })
        .start();
}

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源码分析

1.with方法

public static Option with(Context context) {

    return new Boot(getContextSource(context));
}

public static Option with(Fragment fragment) {

    return new Boot(new SupportFragmentSource(fragment));
}

public static Option with(android.app.Fragment fragment) {

    return new Boot(new FragmentSource(fragment));
}

public static Option with(Activity activity) {

    return new Boot(new ActivitySource(activity));
}

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with方法可以传入Context、Fragment、android.app.Fragment fragment、Activity，返回的都是Option对象，而它是个接口，我们来看看Option的实现类Boot

public class Boot implements Option {
    public Boot(Source source) {
        this.mSource = source;
    }
    @Override
    public RuntimeOption runtime() {
        return new Runtime(mSource);
    }
    @Override
    public InstallRequest install() {
        return INSTALL_REQUEST_FACTORY.create(mSource);
    }
    @Override
    public OverlayRequest overlay() {
        return OVERLAY_REQUEST_FACTORY.create(mSource);
    }
    @Override
    public NotifyOption notification() {
        return new Notify(mSource);
    }
    @Override
    public Setting setting() {
        return new Setting(mSource);
    }
}
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可以看到，这里对不同的Request做了封装，对以后的扩展非常有利，这也是AndPermission的亮点之一。

之前传入的Context、Fragment、android.app.Fragment fragment、Activity只影响的startActivity、startActivityForResult、isShowRationalePermission方法

Source相关代码

public abstract void startActivity(Intent intent);
    public abstract void startActivityForResult(Intent intent, int requestCode);
    public abstract boolean isShowRationalePermission(String permission);
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ActivitySource相关代码

public class ActivitySource extends Source {
    @Override
    public void startActivity(Intent intent) {
        mActivity.startActivity(intent);
    }
    @Override
    public void startActivityForResult(Intent intent, int requestCode) {
        mActivity.startActivityForResult(intent, requestCode);
    }
    @Override
    public boolean isShowRationalePermission(String permission) {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) return false;
        return mActivity.shouldShowRequestPermissionRationale(permission);
    }
}
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2.permission

@Override

public PermissionRequest permission(@NonNull String... permissions) {
    //是否在`manifest.xml`中注册
    checkPermissions(permissions);
    return FACTORY.create(mSource).permission(permissions);
}

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这里首先对传入的权限做了检查，是否在manifest.xml中注册，然后调用FACTORY.create创建了一个PermissionRequest

static {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            FACTORY = new MRequestFactory();
        } else {
            FACTORY = new LRequestFactory();
        }
    }
    public interface PermissionRequestFactory {
        PermissionRequest create(Source source);
    }
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3.rationale相当于是个拦截器，当没有权限时会执行。

这个有什么用呢？比如说，App需要申请全局悬浮窗权限，相比直接跳到授权页，弹个提示框由用户选择是否去授权就显得友好的多。当showRationale()被回调后说明没有权限，此时开发者必须回调RequestExecutor#execute()来启动设置或者RequestExecutor#cancel()来取消启动设置，否则将不会回调onGranted()或者onDenied()中的任何一个，也就是说AndPermission将不会有任何响应。

4.onGranted同意授权时调用，onDenied拒绝授权时调用
5.start开始授权

MRequest相关代码如下

@Override
    public void start() {
        List<String> deniedList = getDeniedPermissions(STANDARD_CHECKER, mSource, mPermissions);
        mDeniedPermissions = deniedList.toArray(new String[deniedList.size()]);
        if (mDeniedPermissions.length > 0) {
            List<String> rationaleList = getRationalePermissions(mSource, mDeniedPermissions);
            if (rationaleList.size() > 0) {
                mRationale.showRationale(mSource.getContext(), rationaleList, this);
            } else {
                execute();
            }
        } else {
            onCallback();
        }
    }
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首先，判断传递进来的权限有哪些是没有已授权，如都已授权，直接回调成功；如有未授权的，先判断是否有需要拦截的，如没有，则调用execute方法

public void execute() {
        BridgeRequest request = new BridgeRequest(mSource);
        request.setType(BridgeRequest.TYPE_PERMISSION);
        request.setPermissions(mDeniedPermissions);
        request.setCallback(this);
        RequestManager.get().add(request);
    }
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RequestManager 它的核心是个线程池

相关方法

private RequestManager() {
        this.mQueue = new LinkedBlockingQueue<>();
        new RequestExecutor(mQueue).start();
    }
    public void add(BridgeRequest request) {
        mQueue.add(request);
    }
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RequestExecutor相关方法

public void run() {
        while (true) {
            synchronized (this) {
                try {
                    mRequest = mQueue.take();
                } catch (InterruptedException e) {
                    continue;
                }
                mMessenger = new Messenger(mRequest.getSource().getContext(), this);
                mMessenger.register();
                executeCurrent();
                try {
                    wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    private void executeCurrent() {
            ...省略...
            case BridgeRequest.TYPE_PERMISSION: 
                BridgeActivity.requestPermission(mRequest.getSource(), mRequest.getPermissions());
                break;
            ...省略...
    }
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再来看看 BridgeActivity.requestPermission

static void requestPermission(Source source, String[] permissions) {
        Intent intent = new Intent(source.getContext(), BridgeActivity.class);
        intent.putExtra(KEY_TYPE, BridgeRequest.TYPE_PERMISSION);
        intent.putExtra(KEY_PERMISSIONS, permissions);
        source.startActivity(intent);
    }
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BridgeActivity相关代码

@Override
    protected void onCreate(Bundle savedInstanceState) {
                 ...省略...
                 String[] permissions = intent.getStringArrayExtra(KEY_PERMISSIONS);
                requestPermissions(permissions, BridgeRequest.TYPE_PERMISSION);
                 ...省略...
     }
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看到这里大家就比较熟悉了，最后我们在看看授权的回调处理

@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        Messenger.send(this);
        finish();
    }
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Messenger相关代码

public static void send(Context context) {
        Intent broadcast = new Intent(ACTION);
        context.sendBroadcast(broadcast);
    }
    @Override
    public void onReceive(Context context, Intent intent) {
        mCallback.onCallback();
    }
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这里回调到了RequestExecutor#onCallback方法，而其又回调到了MRequest#onCallback方法

MRequest相关代码

@Override
    public void onCallback() {
        new AsyncTask<Void, Void, List<String>>() {
            @Override
            protected List<String> doInBackground(Void... voids) {
                return getDeniedPermissions(DOUBLE_CHECKER, mSource, mPermissions);
            }
            @Override
            protected void onPostExecute(List<String> deniedList) {
                if (deniedList.isEmpty()) {
                    callbackSucceed();
                } else {
                    callbackFailed(deniedList);
                }
            }
        }.execute();
    }
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这里再次对传入的权限做检查，如果没有未授权，则回调成功，否则回调失败。

6.用户拒绝授权时提示

if (AndPermission.hasAlwaysDeniedPermission(MainActivity.this, permissions)) {

                    showSettingDialog(MainActivity.this, permissions);
                }

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最终调用的逻辑是在SettingPage#start方法，这里对不同的机型做了适配

public void start(int requestCode) {
        Intent intent;
        if (MARK.contains("huawei")) {
            intent = huaweiApi(mSource.getContext());
        } else if (MARK.contains("xiaomi")) {
            intent = xiaomiApi(mSource.getContext());
        } else if (MARK.contains("oppo")) {
            intent = oppoApi(mSource.getContext());
        } else if (MARK.contains("vivo")) {
            intent = vivoApi(mSource.getContext());
        } else if (MARK.contains("meizu")) {
            intent = meizuApi(mSource.getContext());
        } else {
            intent = defaultApi(mSource.getContext());
        }
        try {
            mSource.startActivityForResult(intent, requestCode);
        } catch (Exception e) {
            intent = defaultApi(mSource.getContext());
            mSource.startActivityForResult(intent, requestCode);
        }
    }
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