清除onNavigationItemSelectedListener中的缓存

Question

根据这个post，我想通过点击导航抽屉中的一些元素来删除程序的缓存。

我已在MainActivity.java上尝试使用此代码段来删除onNavigationItemSelectedListener中的缓存，但它无效。

onNavigationItemSelectedListener方法中的onCreate()

 //-------------------------------------- find navigation view
    NavigationView navigationView = (NavigationView)findViewById(R.id.xmlNavigation);
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {
            int itemId = menuItem.getItemId();
            if(itemId == R.id.star){

                  ===>  deleteCache(MainActivity.this);
                  ===>   deleteDir(MainActivity.this.getCacheDir());

               Toast.makeText(MainActivity.this , "cache is deleted!" , Toast.LENGTH_SHORT).show();
            }
            menuItem.setChecked(true);
            mDrawerLayout.closeDrawers();
            //Toast.makeText(MainActivity.this , menuItem.getTitle() , Toast.LENGTH_SHORT).show();
            return true;
        }
    });


}

此代码段来自onCreate()和MainActivity.java：

///====================================================== snippet for deleting the cache

public static void deleteCache(Context context) {
    try {
        File dir = context.getCacheDir();
        if (dir != null && dir.isDirectory()) {
            deleteDir(dir);
        }
    } catch (Exception e) {}
}

public static boolean deleteDir(File dir) {
    if (dir != null && dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            boolean success = deleteDir(new File(dir, children[i]));
            if (!success) {
                return false;
            }
        }
    }
    return dir.delete();
}

///====================================================== #snippet for deleting the cache