Android Fragment 从源码的角度去解析（上）

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public static class ExampleFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.example_fragment,
container, false);
}
}

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment android:name="com.example.news.ExampleFragment"
android:id="@+id/list"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent" />
</LinearLayout>

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/root_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
android:fitsSystemWindows="true"
android:orientation="vertical">
<FrameLayout

android:id="@+id/main_tab_fl"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1" />
<RadioGroup

android:background="@color/title_bar_bg_day"
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="@dimen/tab_height"
android:layout_alignParentBottom="true"
android:gravity="bottom"
android:orientation="horizontal">
<RadioButton

android:id="@+id/home_rb"
style="@style/home_bottom_tab_style"
android:drawableTop="@drawable/ic_tab_home"
android:text="首页" />
<RadioButton

android:id="@+id/find_rb"
style="@style/home_bottom_tab_style"
android:drawableTop="@drawable/ic_tab_discovery"
android:text="发现" />
<RadioButton

android:id="@+id/new_rb"
style="@style/home_bottom_tab_style"
android:drawableTop="@drawable/ic_tab_fresh"
android:text="新鲜" />
<RadioButton

android:id="@+id/message_rb"
style="@style/home_bottom_tab_style"
android:drawableTop="@drawable/ic_tab_msg"
android:text="消息" />
</RadioGroup>
</LinearLayout>

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FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

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HomeFragment fragment = new HomeFragment();
fragmentTransaction.add(R.id.main_tab_fl, fragment);
fragmentTransaction.commit();

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public class FindFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(
R.layout.fragment_layout, null);
TextView contentTv = (TextView)
rootView.findViewById(R.id.content_tv);
contentTv.setText("发现");
return rootView;
}
}

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public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private HomeFragment mHomeFragment;
private FindFragment mFindFragment;
private NewFragment mNewFragment;
private MessageFragment mMessageFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.home_rb).setOnClickListener(this);
findViewById(R.id.find_rb).setOnClickListener(this);
findViewById(R.id.new_rb).setOnClickListener(this);
findViewById(R.id.message_rb).setOnClickListener(this);
// 默认一进入页面就添加主Fragment
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
mHomeFragment = new HomeFragment();
fragmentTransaction.add(R.id.main_tab_fl, mHomeFragment);
// 最后记得提交
fragmentTransaction.commit();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.home_rb:
homeRbClick();
break;
case R.id.find_rb:
findRbClick();
break;
case R.id.new_rb:
newRbClick();
break;
case R.id.message_rb:
messageRbClick();
break;
}
}
private void homeRbClick() {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
// 替换成当前页面
fragmentTransaction.replace(R.id.main_tab_fl, mHomeFragment);
fragmentTransaction.commit();
}
private void findRbClick() {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
if (mFindFragment == null) {
mFindFragment = new FindFragment();
}
fragmentTransaction.replace(R.id.main_tab_fl, mFindFragment);
fragmentTransaction.commit();
}
private void newRbClick() {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
if (mNewFragment == null) {
mNewFragment = new NewFragment();
}
fragmentTransaction.replace(R.id.main_tab_fl, mNewFragment);
fragmentTransaction.commit();
}
private void messageRbClick() {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
if (mMessageFragment == null) {
mMessageFragment = new MessageFragment();
}
fragmentTransaction.replace(R.id.main_tab_fl, mMessageFragment);
fragmentTransaction.commit();
}
}