android:fragment的生命周期

一，fragment生命周期以及和activity生命周期的关系

和activity生命周期的关系

二，代码：

viewpager2的两个fragment

cate1

package com.example.okdemo1.fragment;

import android.app.Activity;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.okdemo1.R;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link Cate1Fragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class Cate1Fragment extends Fragment {

    private final String TAG = "Cate1碎片";

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public Cate1Fragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment cate1Fragment.
     */
    // TODO: Rename and change types and number of parameters
    public static Cate1Fragment newInstance(String param1, String param2) {
        Cate1Fragment fragment = new Cate1Fragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "--"+TAG+"->>onCreate");
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.i(TAG, "--"+TAG+"->>onCreateView");
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_cate1, container, false);
    }


    @Override
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
         Log.i(TAG, "--"+TAG+"->>onViewCreated");
     }


     //和activity一致
     @Override
     public void onStart() {
         // TODO Auto-generated method stub
         super.onStart();
         Log.i(TAG, "--"+TAG+"->>onStart");
     }

     //和activity一致
     @Override
     public void onResume() {
         // TODO Auto-generated method stub
         super.onResume();
         Log.i(TAG, "--"+TAG+"->>onResume");
     }

     //和activity一致
     @Override
     public void onPause() {
         // TODO Auto-generated method stub
         super.onPause();
         Log.i(TAG, "--"+TAG+"->>onPause");
     }

     //和activity一致
     @Override
     public void onStop() {
         // TODO Auto-generated method stub
         super.onStop();
         Log.i(TAG, "--"+TAG+"->>onStop");
     }

     //表示fragment销毁相关联的UI布局
     @Override
     public void onDestroyView() {
         // TODO Auto-generated method stub
         super.onDestroyView();
         Log.i(TAG, "--"+TAG+"->>onDestroyView");
     }

     //销毁fragment对象
     @Override
     public void onDestroy() {
         // TODO Auto-generated method stub
         super.onDestroy();
         Log.i(TAG, "--"+TAG+"->>onDestroy");
     }

     //脱离activity
     @Override
     public void onDetach() {
         // TODO Auto-generated method stub
         super.onDetach();
         Log.i(TAG, "--"+TAG+"->>onDetach");
     }


}

cate2

package com.example.okdemo1.fragment;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.okdemo1.R;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link Cate2Fragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class Cate2Fragment extends Fragment {

    private final String TAG = "Cate2碎片";
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public Cate2Fragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment cate2Fragment.
     */
    // TODO: Rename and change types and number of parameters
    public static Cate2Fragment newInstance(String param1, String param2) {
        Cate2Fragment fragment = new Cate2Fragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "--"+TAG+"->>onCreate");
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.i(TAG, "--"+TAG+"->>onCreateView");
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_cate2, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Log.i(TAG, "--"+TAG+"->>onViewCreated");
    }


    //和activity一致
    @Override
    public void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        Log.i(TAG, "--"+TAG+"->>onStart");
    }

    //和activity一致
    @Override
    public void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        Log.i(TAG, "--"+TAG+"->>onResume");
    }

    //和activity一致
    @Override
    public void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        Log.i(TAG, "--"+TAG+"->>onPause");
    }

    //和activity一致
    @Override
    public void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        Log.i(TAG, "--"+TAG+"->>onStop");
    }

    //表示fragment销毁相关联的UI布局
    @Override
    public void onDestroyView() {
        // TODO Auto-generated method stub
        super.onDestroyView();
        Log.i(TAG, "--"+TAG+"->>onDestroyView");
    }

    //销毁fragment对象
    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        Log.i(TAG, "--"+TAG+"->>onDestroy");
    }

    //脱离activity
    @Override
    public void onDetach() {
        // TODO Auto-generated method stub
        super.onDetach();
        Log.i(TAG, "--"+TAG+"->>onDetach");
    }


}

两者代码基本一致，
放到一个viewpager2中，
观察切换时的效果

三，测试效果:

activity启动时:

滑动到第二个fragment时

注意此时cate1变pause

滑动回到第一个fragment时

退出时

四，状态说明：

是否可见

onStart()：执行该方法时，Fragment由不可见变为可见状态。
onStop()：执行该方法时，Fragment完全不可见。

是否可交互

onResume()：执行该方法时，Fragment处于活动状态，用户可与之交互。
onPause()：执行该方法时，Fragment处于暂停状态，但依然可见，用户不能与之交互。