Google 2018 I/O大会上,谷歌隆重推出一个新的架构组件:Navigation，它提供了多Fragment之间的转场，栈管理，帮助你更轻松的使用Fragment；
简单使用：
下面的例子采用androidx+java的形式书写：
- build.gradle
dependencies {
implementation "androidx.navigation:navigation-fragment:2.0.0"
implementation "androidx.navigation:navigation-ui:2.0.0"
}
2.新建两个fragment
fragment_first.xml
fragment_second.xml
- 创建导航视图文件
在res目录下新建navigation文件夹，然后新建一个navigation资源文件nav_fragment.xml,
app:startDestination：默认的起始位置
- 在activity布局中添加fragment组件
android:name：值必须是androidx.navigation.fragment.NavHostFragment，声明这是一个NavHostFragment
app:navGraph：存放的是第3步建好导航的资源文件
app:defaultNavHost="true"：与系统的返回按钮相关联
MainActivity.java
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onSupportNavigateUp() {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment);
return NavHostFragment.findNavController(fragment).navigateUp();
}
}
重写onSupportNavigateUp（）方法，目的是将back事件委托出去。若栈中有两个以上Fragment，点击back键就会返回到上一个Fragment。
- 在Fragment中设置相应的跳转事件
public class FirstFragment extends Fragment {
public FirstFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btnNext = view.findViewById(R.id.btn_next);
btnNext.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Navigation.findNavController(v).navigate(R.id.action_firstFragment_to_secondFragment);
}
});
}
}
public class SecondFragment extends Fragment {
public SecondFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_second, container, false);
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btnBack = view.findViewById(R.id.btn_back);
btnBack.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Navigation.findNavController(v).navigateUp();
}
});
}
}
跳转到activity
修改nav_fragment.xml
FirstFragment.xml
增加跳转到activity的操作，并在跳转到fragment的操作中传值
public class FirstFragment extends Fragment {
public FirstFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
//跳转到下一个fragment, 并传值
Button btnNext = view.findViewById(R.id.btn_next);
btnNext.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Bundle bundle = new Bundle();
bundle.putString("name","from firstFragment");
Navigation.findNavController(v).navigate(R.id.action_firstFragment_to_secondFragment,bundle);
}
});
//跳转到activity
Button btnJumpA = view.findViewById(R.id.btn_jumpA);
btnJumpA .setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Navigation.findNavController(v).navigate(R.id.action_firstFragment_to_activity);
}
});
}
}
SecondFragment接收传来的值
public class SecondFragment extends Fragment {
public SecondFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_second, container, false);
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btnBack = view.findViewById(R.id.btn_back);
btnBack.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Navigation.findNavController(v).navigateUp();
}
});
TextView tv_tip = view.findViewById(R.id.tv_tip);
Bundle bundle = getArguments();
if(bundle.getString("name") != null) {
String name = bundle.getString("name");
tv_tip.setText("This is secondFragment, "+name);
}
}
}