Android Activity和Fragment生命周期

程序员文章站 2022-05-14 08:05:57

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写在前边：

感觉要暂时放弃自己钟爱的computer graphics转战安卓开发了，心里还是有一点不开心。。。。但是我不会放弃CG的！！

想要把自己平时积累的知识记录下来，以便将来回来看看，同时也希望能帮到有需要的人。

正文：

在Android中，activity和fragment的生命周期一直很繁琐，有时候也是傻傻分不清楚，先贴两张图，分别对应activity和fragment的生命周期：

下图为Activity的生命周期：

Android Activity和Fragment生命周期

下图为Fragment的生命周期：

Android Activity和Fragment生命周期

通常情况下，我们要在一个Activity中的OnCreate方法里inflate一个fragment. (原谅我真的不知道中文翻译是什么-.-)，然后调用getFragmentManager进行替换。这个fragment会依赖于它的宿主activity，同生同死的关系。接下来我们用一个demo来说明两者之间的联系。

情景不复杂，直接上代码吧

1. MainActivity.java

布局文件中只有一个按钮，是用来进行第二步测试的，现在可以不理会

package com.example.zach.demo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportFragmentManager().beginTransaction().add(R.id.content, new frag_one()).addToBackStack(null).commit();
        Log.d("Activity onCreate()", "TAG");
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d("Activity onStart()", "TAG");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d("Activity onResume()", "TAG");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d("Activity onPause()", "TAG");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d("Activity onStop()", "TAG");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d("Activity onDestroy()", "TAG");
    }
}

2. frag_one.java

package com.example.zach.demo;

import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

/**
 * Created by zhangwenpurdue on 7/20/2017.
 */

public class frag_one extends Fragment {
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d("Frag 1 - onAttach()", "TAG");

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.frag_one_layout, container, false);
        Button button = v.findViewById(R.id.gotosecond);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getFragmentManager().beginTransaction().replace(R.id.content, new frag_two()).addToBackStack(null).commit();
                //getFragmentManager().beginTransaction().replace(R.id.content, new frag_two()).commit();


            }
        });
        Log.d("Frag 1 - onCreateView", "TAG");
        return v;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
        Log.d("Frag 1 - onCreate", "TAG");
    }


    @Override
    public void onStart() {
        super.onStart();
        Log.d("Frag 1 - onStart()", "TAG");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d("Frag 1 - onResume()", "TAG");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d("Frag 1 - onPause()", "TAG");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d("Frag 1 - onStop()", "TAG");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d("Frag 1 - DestroyView()", "TAG");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("Farg 1 - onDestroy()", "TAG");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d("Frag 1 - onDetach()", "TAG");
    }
}

3. frag_two.java

package com.example.zach.demo;

import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

/**
 * Created by zhangwenpurdue on 7/20/2017.
 */

public class frag_two extends Fragment {
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d("Frag 2 - onAttach()", "TAG");

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.frag_two_layout, container, false);
        Log.d("Frag 2 - onCreateView", "TAG");
        return v;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("Frag 2 - onCreate", "TAG");
    }



    @Override
    public void onStart() {
        super.onStart();
        Log.d("Frag 2 - onStart()", "TAG");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d("Frag 2 - onResume()", "TAG");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d("Frag 2 - onPause()", "TAG");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d("Frag 2 - onStop()", "TAG");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d("Frag 2 - DestroyView()", "TAG");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("Frag 2 - onDestroy()", "TAG");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d("Frag 2 - onDetach()", "TAG");
    }
}

当我们运行程序，mainactivity被创建，第一个fragment被添加到主页面上，此时的log是这样的：

Android Activity和Fragment生命周期