一、Fragment与Activity的生命周期
Fragment生命周期：
Fragment生命周期.jpg
二、Fragment的使用，实现底部菜单切换
(一)、先介绍两个使用Fragment的两个类：
1. FragmentManager manager
getSupportFragmentManager()：用于管理FragmentManager
2. FragmentTransaction ：用于管理事务的处理
FragmentTransacion ft=manager.beginTransaction();
- 能对Fragment进行增加、删除、替换等操作。replace()会将fragment重新创建和销毁。
- 每个事务可保存在Activity的后退栈中,如此用户能在fragment之间导航。
- 切换Fragment时，Fragment被切换时，Fragment被销毁和重新创建；
(二)、实现底部菜单切换
有两种方式：
1. 第一种是使用FragmentTransaction的replace()方法
Activity布局：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="cn.ucai.dayfragment_activity.MainActivity">
<FrameLayout
android:id="@+id/fragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@+id/linear"
/>
<LinearLayout
android:id="@+id/linear"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_alignParentBottom="true"
>
<TextView
android:id="@+id/tvNewGoods"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dp"
android:layout_weight="1"
android:onClick="onClick"
android:text="新品"
/>
<TextView
android:id="@+id/tvBoutique"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dp"
android:layout_weight="1"
android:onClick="onClick"
android:text="精选"
/>
<TextView
android:id="@+id/tvCategory"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dp"
android:layout_weight="1"
android:onClick="onClick"
android:text="分类"
/>
<TextView
android:id="@+id/tvCart"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dp"
android:onClick="onClick"
android:layout_weight="1"
android:text="购物车"
/>
<TextView
android:id="@+id/tvMine"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dp"
android:onClick="onClick"
android:layout_weight="1"
android:text="我"
/>
</LinearLayout>
</RelativeLayout>
2、实现的点击方法
public class MainActivity extends AppCompatActivity {
NewsGoodsFragment newsGoodsFragment;
BoutiqueFragment boutiqueFragment;
CategoryFragment categoryFragment;
CartFragment cartFragment;
MineFragment mineFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onClick(View view){
FragmentManager manager=getSupportFragmentManager();
FragmentTransaction fragmentTransaction=manager.beginTransaction();
switch (view.getId()){
case R.id.tvNewGoods:
if(newsGoodsFragment==null){
newsGoodsFragment=new NewsGoodsFragment();
fragmentTransaction.replace(R.id.fragment,newsGoodsFragment);
fragmentTransaction.commit();
}else{
fragmentTransaction.replace(R.id.fragment,newsGoodsFragment);
fragmentTransaction.commit();
}
break;
case R.id.tvBoutique:
if(boutiqueFragment==null){
boutiqueFragment=new BoutiqueFragment();
fragmentTransaction.replace(R.id.fragment,boutiqueFragment);
fragmentTransaction.commit();
}else{
fragmentTransaction.replace(R.id.fragment,boutiqueFragment);
fragmentTransaction.commit();
}
break;
case R.id.tvCategory:
if(categoryFragment==null){
categoryFragment=new CategoryFragment();
fragmentTransaction.replace(R.id.fragment,categoryFragment);
fragmentTransaction.commit();
}else{
fragmentTransaction.replace(R.id.fragment,categoryFragment);
fragmentTransaction.commit();
}
break;
case R.id.tvCart:
if (cartFragment==null){
cartFragment=new CartFragment();
fragmentTransaction.replace(R.id.fragment,cartFragment);
fragmentTransaction.commit();
}else{
fragmentTransaction.replace(R.id.fragment,cartFragment);
fragmentTransaction.commit();
}
break;
case R.id.tvMine:
if (mineFragment==null){
mineFragment=new MineFragment();
fragmentTransaction.replace(R.id.fragment,mineFragment);
fragmentTransaction.commit();
}else{
fragmentTransaction.replace(R.id.fragment,mineFragment);
fragmentTransaction.commit();
}
break;
}
}
}
2. 第二种是先初始化fragment，将fragment添加到该Activity的FragmentManager管理器中，
再记录当前点击的位置进行切换fragment；
public class MainActivity extends AppCompatActivity {
NewsGoodsFragment newsGoodsFragment;
BoutiqueFragment boutiqueFragment;
CategoryFragment categoryFragment;
CartFragment cartFragment;
MineFragment mineFragment;
Fragment fragment[];
int currentIndex = 0;
int index = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addFragment();
}
private void addFragment() {
newsGoodsFragment = new NewsGoodsFragment();
boutiqueFragment = new BoutiqueFragment();
cartFragment = new CartFragment();
categoryFragment = new CategoryFragment();
mineFragment = new MineFragment();
fragment = new Fragment[5];
fragment[0] = newsGoodsFragment;
fragment[1] = boutiqueFragment;
fragment[2] = categoryFragment;
fragment[3] = cartFragment;
fragment[4] = mineFragment;
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.fragment, newsGoodsFragment);
transaction.add(R.id.fragment, boutiqueFragment);
transaction.add(R.id.fragment, categoryFragment);
transaction.add(R.id.fragment, cartFragment);
transaction.add(R.id.fragment, mineFragment);
transaction.show(newsGoodsFragment);
transaction.hide(boutiqueFragment);
transaction.hide(cartFragment);
transaction.hide(categoryFragment);
transaction.hide(mineFragment);
transaction.commit();
}
public void onClick(View view) {
switch (view.getId()) {
case R.id.tvNewGoods:
index = 0;
break;
case R.id.tvBoutique:
index = 1;
break;
case R.id.tvCategory:
index = 2;
break;
case R.id.tvCart:
index = 3;
break;
case R.id.tvMine:
index = 4;
break;
}
if (currentIndex != index) {
setFragment();
}
}
private void setFragment() {
getSupportFragmentManager().beginTransaction().
hide(fragment[currentIndex]).show(fragment[index]).commit();
currentIndex = index;
}
}
三、FragmentActivity
FragmentActivity用来解决android3.0之前没有fragment的API
通过继承 FragmentActivity，在Android3之前的手机中的Activity中就能使用Fragment
四、Fragment的startActivityForResult
- 若调用Fragment.startActivityForActivity方法，则返回的结果首先被Fragment.onActivityResult方法处理，然后传递到宿主Activity的onActivityResult方法.
- 若在Fragment中调用的是宿主Activity的startActivityForActivity，则返回的结果被苏浙Activity.onActivityResult()方法处理
五、Fragment与Activity的通信
