文章目錄
- 1導包
- 2 navigation導航檔案
- 3 首頁面
- 4 三個Fragment
- 5 遺留問題
參考:
https://developer.android.google.cn/guide/navigation/
https://developer.android.google.cn/guide/navigation/navigation-getting-started
https://www.jianshu.com/p/0bb65607bdf8
闡述Navigation如何管理MainActivity中的MainPage1Fragment、MainPage2Fragment、MainPage3Fragment三個fragment。
1導包
def nav_version = "2.1.0"
// Java language implementation
implementation "androidx.navigation:navigation-fragment:$nav_version"
implementation "androidx.navigation:navigation-ui:$nav_version"
2 navigation導航檔案
在app的res目錄下,建立一個navigation檔案夾,在此檔案夾下新增一個navigation的xml檔案,此處新增一個 nav_graph_main.xml,内容如下:
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/nav_graph_main.xml"
app:startDestination="@id/page1Fragment">
<fragment
android:id="@+id/page1Fragment"
android:name="com.hongx.navigation.MainPage1Fragment"
android:label="fragment_page1"
tools:layout="@layout/fragment_main_page1">
<!--
action:程式中使用id跳到destination對應的類
-->
<action
android:id="@+id/action_page2"
app:destination="@id/page2Fragment" />
</fragment>
<fragment
android:id="@+id/page2Fragment"
android:name="com.hongx.navigation.MainPage2Fragment"
android:label="fragment_page2"
tools:layout="@layout/fragment_main_page2">
<action
android:id="@+id/action_page1"
app:destination="@id/page1Fragment" />
<action
android:id="@+id/action_page3"
app:destination="@id/page3Fragment" />
</fragment>
<!-- <navigation-->
<!-- android:id="@+id/nav_graph_page3"-->
<!-- app:startDestination="@id/page3Fragment">-->
<fragment
android:id="@+id/page3Fragment"
android:name="com.hongx.navigation.MainPage3Fragment"
android:label="fragment_page3"
tools:layout="@layout/fragment_main_page3">
<action
android:id="@+id/action_page2"
app:destination="@id/page2Fragment" />
</fragment>
<!-- </navigation>-->
</navigation>
在Design中可以看到非常直覺的fragment切換流程,如下:
![](https://img.laitimes.com/img/__Qf2AjLwojIjJCLyojI0JCLiAzNfRHLGZkRGZkRfJ3bs92YsYTMfVmepNHL0cGRPRTVXRGNk1mY2hmMMBjVtJWd0ckW65UbM5WOHJWa5kHT20ESjBjUIF2X0hXZ0xCMx81dvRWYoNHLrdEZwZ1Rh5WNXp1bwNjW1ZUba9VZwlHdssmch1mclRXY39CXldWYtlWPzNXZj9mcw1ycz9WL49zZuBnLyYzNzUTNzgDM0IjMxkTMwIzLc52YucWbp5GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.png)
3 首頁面
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<!--
android:name="androidx.navigation.fragment.NavHostFragment"
name 必須指定,表示這是一個可以切換fragment的控件
app:defaultNavHost="true"
攔截系統back鍵,在fragment中就可以用back回退上一個fragment
app:navGraph="@navigation/nav_graph_main"
連接配接使用nav_graph_main.xml,擷取fragment之間的導航結構
-->
<fragment
android:id="@+id/my_nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph_main" />
</androidx.constraintlayout.widget.ConstraintLayout>
-
app:defaultNavHost=“true”
攔截系統back鍵,在fragment中就可以用back回退上一個fragment
-
app:navGraph="@navigation/nav_graph_main"
連接配接使用nav_graph_main.xml,擷取fragment之間的導航結構
-
android:name=“androidx.navigation.fragment.NavHostFragment”
name 必須指定,表示這是一個可以切換fragment的控件
4 三個Fragment
public class MainPage1Fragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main_page1, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btn = view.findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Navigation.findNavController(view).navigate(R.id.action_page2);
}
});
}
}
public class MainPage2Fragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main_page2, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btn = view.findViewById(R.id.btn);
//傳回MainPage1Fragment
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Navigation.findNavController(view).navigate(R.id.action_page1);
}
});
Button btn2 = view.findViewById(R.id.btn2);
//前往MainPage3Fragment
btn2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Navigation.findNavController(view).navigate(R.id.action_page3);
}
});
}
}
public class MainPage3Fragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main_page3, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btn = view.findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Navigation.findNavController(view).navigate(R.id.action_page2);
//回退上一步
// Navigation.findNavController(view).navigateUp();
}
});
}
}
-
Navigation.findNavController(view).navigate(R.id.action_page2);
實作了點選按鈕後Fragment頁面的跳轉
5 遺留問題
盡管通過Navigation方式管理Fragment的代碼簡潔而且直覺,但是有一個非常緻命的問題,就是同一個Fragment會被重複建立,這樣會導緻每次切換fragment的時候都會重新去請求資料,非常浪費系統資源,而且降低了APP的使用者體驗。
解決辦法:https://blog.csdn.net/hongxue8888/article/details/103677070
Github:
https://github.com/345166018/HxJetpack/tree/master/HxNavigation