位运算的简单应用-权限管理，

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位运算的简单应用-权限管理

位运算在实际的开发中，有很多巧妙的应用场景。如：

    public void setFlags(int flags, int mask) {
        final WindowManager.LayoutParams attrs = getAttributes();
        attrs.flags = (attrs.flags&~mask) | (flags&mask);
        mForcedWindowFlags |= mask;
        dispatchWindowAttributesChanged(attrs);
    }

下面利用位运算来简单模拟权限管理

权限管理类

public class PermissionManager {

    public static final int PERMISSION_NONE = 1;

    public static final int PERMISSION_A = 1 << 1;

    public static final int PERMISSION_B = 1 << 2;

    public static final int PERMISSION_C = 1 << 3;

    public static final int PERMISSION_D = 1 << 4;

    private int mPermission = PERMISSION_NONE;

    private static class PermissionManagerHolder {
        static PermissionManager sPermissionManager = new PermissionManager();
    }

    private PermissionManager() {

    }

    public static PermissionManager getInstance() {
        return PermissionManagerHolder.sPermissionManager;
    }

    /**
     * 添加权限
     * @param permission
     */
    public void addPermission(int permission) {
        if (hasPermission(permission)) {
            return;
        }
        mPermission |= permission;
    }

    /**
     * 移除权限
     * @param permission
     */
    public void removePermission(int permission) {
        if (!hasPermission(permission)) {
            return;
        }
        mPermission &= ~permission;
    }

    /**
     * 判断是否有权限
     * @param permission
     * @return
     */
    public boolean hasPermission(int permission) {
        return (mPermission & permission) != 0;
    }

}

使用

public static void main(String[] args) {
        System.out.println("没有添加任何权限----------");
        PermissionManager permissionManager = PermissionManager.getInstance();
        checkPermission(permissionManager);
        System.out.println("添加权限A----------");
        System.out.println("添加权限B----------");
        System.out.println("添加权限C----------");
        permissionManager.addPermission(PermissionManager.PERMISSION_A);
        permissionManager.addPermission(PermissionManager.PERMISSION_B);
        permissionManager.addPermission(PermissionManager.PERMISSION_C);
        checkPermission(permissionManager);
        System.out.println("删除权限C----------");
        permissionManager.removePermission(PermissionManager.PERMISSION_C);
        checkPermission(permissionManager);
    }

    public static void checkPermission(PermissionManager permissionManager) {
        System.out.println("PERMISSION_A exist:" + permissionManager.hasPermission(PermissionManager.PERMISSION_A));
        System.out.println("PERMISSION_B exist:" + permissionManager.hasPermission(PermissionManager.PERMISSION_B));
        System.out.println("PERMISSION_C exist:" + permissionManager.hasPermission(PermissionManager.PERMISSION_C));
        System.out.println("PERMISSION_D exist:" + permissionManager.hasPermission(PermissionManager.PERMISSION_D));
    }

输出结果:

没有添加任何权限----------
PERMISSION_A exist:false
PERMISSION_B exist:false
PERMISSION_C exist:false
PERMISSION_D exist:false
添加权限A----------
添加权限B----------
添加权限C----------
PERMISSION_A exist:true
PERMISSION_B exist:true
PERMISSION_C exist:true
PERMISSION_D exist:false
删除权限C----------
PERMISSION_A exist:true
PERMISSION_B exist:true
PERMISSION_C exist:false
PERMISSION_D exist:false

位运算并不限于权限管理，具有多个状态的应用场景，都可以用到。