Fragment的切换

实现Frament的动态切换有两种方式

1.切换的时候重新创建Fragment

public void changeFragment(final int id){
	Fragment currentFragment=new PopularFragment();
	FragmentManager fragmentManager = getSupportFragmentManager();
	fragmentManager.beginTransaction()
				.replace(R.id.content_frame, currentFragment).commit();
	}

2.将需要的Frament放进一个数组里面，把这个数组里面不需要的显示的Fragment隐藏，把需要的显示的Fragment展现出来，这样每次切换的时候就不需要重新创建Fragment了，而且，通过这样方式，还能添加切换的Fragment的动画。

实例化Fragment数组

Fragment[] mFragments = new Fragment[3]

mFragments[0] = PopularFragment.newInstance(Category.popular);
<span style="font-family: Arial, Helvetica, sans-serif;">mFragments[1] = PopularFragment.newInstance(Category.everyone);</span>

mFragments[2] = PopularFragment.newInstance(Category.debuts);

FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
		for (Fragment fragment : mFragments) {
			ft.add(R.id.content_frame, fragment);
			ft.hide(fragment);
		}
		ft.commit();

切换方法

private void showOrHideFragments(final int id) {
		FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
		// define replace fragment animation
		ft.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out,
				android.R.anim.fade_in, android.R.anim.fade_out);
		// show or hide fragment
		for (int i = 0; i < mFragments.length; i++) {
			Fragment fragment = mFragments[i];
			if (fragment != null) {
				if (id != i) {
					ft.hide(fragment);
				} else {
					ft.show(fragment);
				}
			}
		}
		ft.commit();
	}

如果遇到Fragment重叠显示的问题，可以这样解决，详见http://typeblog.net/tech/2014/08/22/fix-duplicate-menu.html

         /**
	 * not calling the superclass method doesn't allow the fragment manager to save its state
	 * 解决Fragment和菜单项重叠显示问题
	 */
	@Override
	protected void onSaveInstanceState(Bundle outState) {
		//Empty 
	}