一手遮天 Android - Fragment: Fragment 的生命周期

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd

一手遮天 Android - Fragment: Fragment 的生命周期

示例如下:

/fragment/FragmentDemo1.java

/**
 * Fragment 的生命周期
 *
 * 详见 @drawable/img_fragment_lifecycle 生命周期图，大概说明一下，如下
 * 1、完整的生命周期 onAttach() -> onCreate() -> onCreateView() -> onActivityCreated() - onStart() -> onResume() -> onPause() -> onStop() -> onDestroyView() -> onDestroy() -> onDetach()
 * 2、在 onCreateView() 中加载布局文件
 * 3、父 Activity 的 onCreate() 完成后会调用子 Fragment 的 onActivityCreated()
 * 4、加入 Fragment 返回堆栈，然后再离开的话则会走到 onDestroyView()，恢复时会从 onCreateView() 开始走（这部分请参见 fragment/FragmentDemo2 中的说明）
 *
 *
 * 举个例子：
 * 1、打开 FragmentDemo1（在 xml 中引用了 Fragment1_1）
 * FragmentDemo1: onCreate start
 * Fragment1_1: onAttach
 * Fragment1_1: onCreate
 * Fragment1_1: onCreateView
 * FragmentDemo1: onCreate end
 * FragmentDemo1: onStart start
 * Fragment1_1: onActivityCreated
 * Fragment1_1: onStart
 * FragmentDemo1: onStart end
 * FragmentDemo1: onResume start
 * FragmentDemo1: onResume end
 * Fragment1_1: onResume
 *
 * 2、然后打开另一个 activity
 * FragmentDemo1: onPause start
 * Fragment1_1: onPause
 * FragmentDemo1: onPause end
 * FragmentDemo1: onStop start
 * Fragment1_1: onStop
 * FragmentDemo1: onStop end
 *
 * 3、关闭这个新打开的 activity
 * FragmentDemo1: onStart start
 * Fragment1_1: onStart
 * FragmentDemo1: onStart end
 * FragmentDemo1: onResume start
 * FragmentDemo1: onResume end
 * Fragment1_1: onResume
 *
 * 4、关闭当前 activity
 * FragmentDemo1: onPause start
 * Fragment1_1: onPause
 * FragmentDemo1: onPause end
 * FragmentDemo1: onStop start
 * Fragment1_1: onStop
 * FragmentDemo1: onStop end
 * FragmentDemo1: onDestroy
 * Fragment1_1: onDestroyView
 * Fragment1_1: onDestroy
 * Fragment1_1: onDetach
 * FragmentDemo1: onDestroy
 */

package com.webabcd.androiddemo.fragment;

import android.content.Intent;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.webabcd.androiddemo.R;

public class FragmentDemo1 extends AppCompatActivity {

    private final String LOG_TAG = "FragmentDemo1";

    private Button mButton1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d(LOG_TAG, "onCreate start");

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment_fragmentdemo1);

        // 通过如下方式获取 xml 中的 fragment 对象
        // androidx.fragment.app.Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment1);

        mButton1 = findViewById(R.id.button1);
        mButton1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(FragmentDemo1.this, FragmentDemo1_2.class);
                startActivity(intent);
            }
        });

        Log.d(LOG_TAG, "onCreate end");
    }

    @Override
    protected void onStart() {
        Log.d(LOG_TAG, "onStart start");
        super.onStart();
        Log.d(LOG_TAG, "onStart end");
    }

    @Override
    protected void onResume() {
        Log.d(LOG_TAG, "onResume start");
        super.onResume();
        Log.d(LOG_TAG, "onResume end");
    }

    @Override
    protected void onPause() {
        Log.d(LOG_TAG, "onPause start");
        super.onPause();
        Log.d(LOG_TAG, "onPause end");
    }

    @Override
    protected void onStop() {
        Log.d(LOG_TAG, "onStop start");
        super.onStop();
        Log.d(LOG_TAG, "onStop end");
    }

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

\fragment\FragmentDemo1_2.java

package com.webabcd.androiddemo.fragment;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.webabcd.androiddemo.R;

public class FragmentDemo1_2 extends AppCompatActivity {

    private Button mButton1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment_fragmentdemo1_2);

        mButton1 = findViewById(R.id.button1);
        mButton1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }
}

/layout/activity_fragment_fragmentdemo1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAllCaps="false"
        android:text="启动另一个 activity"/>

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:src="@drawable/img_fragment_lifecycle"/>

    <!--
        fragment - 在 xml 中引用 fragment
            name - 需要引用的 fragment 的类全名
    -->
    <fragment
        android:id="@+id/fragment1"
        android:name="com.webabcd.androiddemo.fragment.Fragment1_1"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>

/layout/activity_fragment_fragmentdemo1_2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAllCaps="false"
        android:text="关闭"/>

</LinearLayout>

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd