小白搞了一天fragment未能动态加载

walkuere 2019-06-20 02:45:47

静态加载发现照抄的可以了
fragment: https://www.cnblogs.com/linfenghp/p/5560015.html

AS 3.3.1
gradle
android.enableJetifier=true
android.useAndroidX=true

compileSdkVersion 28
defaultConfig {
applicationId "com.example.cd2"
minSdkVersion 22
targetSdkVersion 28

动态加载

API28 用androidX
MainActivity.java:





import Fragments.FW_EntryLobby;

import androidx.appcompat.app.AppCompatActivity;

import androidx.fragment.app.FragmentActivity;

import androidx.fragment.app.FragmentManager;

import androidx.fragment.app.FragmentTransaction;





public class MainActivity extends AppCompatActivity {

	public static MainActivity mainstance;

	ViewGroup vg_mainframe;

	FragmentActivity fa;//replaces FragmentManager

	FragmentManager fm;

	FragmentTransaction ft;//FragmentTransaction事务对象

	@Override

	protected void onCreate(Bundle savedInstanceState)

	{

		super.onCreate(savedInstanceState);

		requestWindowFeature(android.view.Window.FEATURE_NO_TITLE);

		setContentView(R.layout.activity_main);

		mainstance=this;

		init_fragments();

		loadWhole();

		init_entrylobby();



	}



	private void init_fragments()//fragment is deprecated since API28

	{

		//https://stackoverflow.com/questions/51737667/since-the-android-getfragmentmanager-api-is-deprecated-is-there-any-alternati

		fa=new FragmentActivity();

		fm = fa.getSupportFragmentManager();

		ft = fm.beginTransaction();

	}

	public void loadWhole()

	{

		vg_mainframe= (ViewGroup) MainActivity.mainstance.findViewById(R.id.fl_am);



	}

	FW_EntryLobby flayout_entrylobby;

	public void init_entrylobby()

	{

		if(flayout_entrylobby==null)

			flayout_entrylobby = new FW_EntryLobby();

		ft.replace(R.id.fl_am,flayout_entrylobby);

		ft.addToBackStack(null);

		ft.commitAllowingStateLoss();//用commit()就报错啊

	}

activity_main.xml:



<?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:layout_width="match_parent"

    android:layout_height="match_parent"

    >

    <FrameLayout

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:id="@+id/fl_am">

    </FrameLayout>



</RelativeLayout>



<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout class="Fragments.FW_EntryLobby"

    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:background="#0000ff"

    >



    <Button

        android:id="@+id/b_entrylobby_fetch"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="0px"

        android:layout_marginTop="0px"

        

        android:text="enter" />



</RelativeLayout>

Fragment类





package Fragments;



import android.os.Bundle;



import androidx.annotation.Nullable;

import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;



import com.example.cd2.R;



public class FW_EntryLobby extends Fragment {

	@Nullable

	@Override

	public View onCreateView(LayoutInflater inflater, ViewGroup container,

	                         Bundle savedInstanceState)

	{



		View rootView = inflater.inflate(R.layout.lf_entrylobby, null);

		return rootView;

	}





}

开始运行就一片白，什么也没有
如果用commit()就是闪退
报错信息
Unable to start activity ComponentInfo{com.example.cd2/com.example.cd2.MainActivity}: java.lang.IllegalStateException: Activity has been destroyed

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