安卓-Activity生命周期

一、简述

android是使用任务来管理活动的，一个任务就是一组存放在栈中的活动的集合。

1.活动有四个状态:
1)运行状态:活动位于返回栈的栈顶
2)暂停状态:活动不处于栈顶位置，但是可见
3)停止状态:活动不处于栈顶位置，且完全不可见
4)销毁状态:当一个活动从返回栈中移除

2.活动生存周期
Activity中定义了7各回调方法
onCreate():活动第一次创建时调用，完成初始化操作:加载布局、绑定事件
onStart():活动由不可见变为可见时调用
onResume():活动准备好和用户交互时调用。处于返回栈的栈顶，并且处于运行状态
onPause():系统准备去启动或者恢复另一个活动时调用。比如：上面弹出各对话框
onStop():活动在完全不可见的时候调用
onDestroy():活动被销毁之前调用
onRestart():活动由停止状态变为运行状态

生命周期又可分为3种生存期
完整生存期:onCreate()到onDestroy()之间
可见生存期:onStart()到onStop()之间
前台生存期:onResume()和onPause()之间

总结下状态的变化:

一个Activity从创建到显示经历:onCreate() onStart() onResume()
一个Activity上弹出一个全屏的Activity,经历:onPause onStop,上面的销毁，onRestart onStart onResume
一个Activity上弹出一个对话框，下面的Activity经历:onPause ,此时点击返回键，下面的Activity执行onResume,再点击返回键，Activity执行onPause onStop onDestroy

下面也引用网上的一张图:

上面这张图是各个文章中引用最多的，详细说明了各个状态。

二、测试各种情况

1)测试一个Activity正常启动时

测试结果:

02-23 18:55:55.524 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onCreate:
02-23 18:55:55.744 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onStart:
02-23 18:55:55.744 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onResume:

可以看到Activity在启动的过程中经历了:onCreate->onStart->onResume

2)从后台切换到前台

测试结果:

02-23 19:21:51.954 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onRestart:
02-23 19:21:51.954 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onStart:

02-23 19:21:51.964 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onResume:

02-23 19:21:52.004 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:

可以看到Activity经历了:onRestart->onStart->onResume->onWindowFocusChanged

3)全屏的Activity跳转且不透明

测试结果:

02-23 19:38:31.854 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onPause:
02-23 19:38:31.874 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:
02-23 19:38:31.904 20215-20215/com.mobile.cdtx.blog D/SecondDemoActivity: onCreate:
02-23 19:38:31.994 20215-20215/com.mobile.cdtx.blog D/SecondDemoActivity: onStart:
02-23 19:38:31.994 20215-20215/com.mobile.cdtx.blog D/SecondDemoActivity: onResume:
02-23 19:38:32.084 20215-20215/com.mobile.cdtx.blog D/SecondDemoActivity: onWindowFocusChanged:
02-23 19:38:32.474 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onStop:

其中ActivityLifeActivity是下面的界面，SecondDemoActivity是跳转后的界面

ActivityLifeActivity经历了:onPause->onWindowFocusChanged->onStop

SecondDemoActivity经历了:onCreate->onStart->onResume->onWindowFocusChanged

4)全屏的Activity返回到下面的Activity

测试结果:

02-23 19:31:59.854 8605-8605/com.mobile.cdtx.blog D/SecondDemoActivity: onPause:
02-23 19:31:59.864 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onRestart:
02-23 19:31:59.864 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onStart:
02-23 19:31:59.864 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onResume:
02-23 19:31:59.894 8605-8605/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:
02-23 19:31:59.964 8605-8605/com.mobile.cdtx.blog D/SecondDemoActivity: onWindowFocusChanged:
02-23 19:32:00.284 8605-8605/com.mobile.cdtx.blog D/SecondDemoActivity: onStop:
02-23 19:32:00.284 8605-8605/com.mobile.cdtx.blog D/SecondDemoActivity: onDestroy:

其中，SecondDemoActivity是上面的界面，ActivityLifeActivity是下面的界面

SecondDemoActivity经历了:onPause->onWindowFocusChanged->onStop->onDestroy

ActivityLifeActivity经历了:onRestart->onStart->onResume->onWindowFocusChanged

5)从前台切换到后台

测试结果:

02-23 19:43:37.854 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onPause:
02-23 19:43:37.874 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:
02-23 19:43:38.354 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onStop:

ActivityLifeActivity从前台切换到后台经历了:onPause->onWindowFocusChanged->onStop

6)Activity上弹出Toast

测试结果:

未打印任何日志,这说明窗口焦点和Activity未受任何影响

7)Activity上弹出对话框

测试结果:

02-23 19:49:10.394 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:

可以看到Activity只经历了:onWindowFocusChanged

8)Activity上弹出的对话框消失

测试结果:

02-23 19:50:34.684 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:

可以看到Activity只经历了:onWindowFocusChanged

9)弹出半透明对话框

测试结果:

02-23 19:52:23.124 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onPause:
02-23 19:52:23.144 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:

可以看到ActivityLifeActivity经历了:onPause->onWindowFocusChanged

10)弹出的半透明对话框消失

02-23 19:54:18.944 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onResume:
02-23 19:54:18.964 20215-20215/com.mobile.cdtx.blog D/ActivityLifeActivity: onWindowFocusChanged:

ActivityLifeActivity经历了:onResume->onWindowFocusChanged

11)改变屏幕方向

然后在“Settings->Display”中，将“Auto-rotate Screen”一项选中，表明可以自动根据方向旋转屏幕,中文设置中显示的是:显示->自动旋转屏幕

测试结果:

02-23 20:03:12.884 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onPause:
02-23 20:03:12.884 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onStop:
02-23 20:03:12.884 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onDestroy:
02-23 20:03:12.924 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onCreate:
02-23 20:03:13.044 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onStart:
02-23 20:03:13.044 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onRestoreInstanceState:
02-23 20:03:13.044 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onResume:
02-23 20:03:13.124 9747-9747/com.mobile.cdtx.blog D/SecondDemoActivity: onWindowFocusChanged:

可以看到Activity经历了:onPause->onStop->onDestroy->onCreate->onStart->onRestoreInstanceState->onResume->onWindowFocusChanged

其中onRestoreInstanceState用于恢复保存的数据

上面的数据说明经历销毁到重建的过程，怎么样才可以避免这种情况呢?

1.AndroidManifest.xml中声明:<uses-permission android:name="android.permission.CHANGE_CONFIGURATION"/>

2.在Activity的注册中设置:android:configChanges="orientation|screenSize“属性

3.在Activity中重写下面的方法:

@Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        if(this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE)
        {
            Log.d(TAG, "onConfigurationChanged:横屏");// 获取横屏
        } else if(this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
        {// 获取竖屏
            Log.d(TAG, "onConfigurationChanged:竖屏");// 获取横屏
        }
    }

测试结果:

02-23 20:27:29.034 9379-9379/com.mobile.cdtx.blog D/SecondDemoActivity: onConfigurationChanged:横屏

可以看到Activity并没有经历销毁到重建的过程。

有些文章上说android:configChanges="orientation“这个属性这样设置，但是在新高版本的API中不行仍然会经历从销毁到重建的过程。自从Android 3.2（API 13），screen size也开始跟着设备的横竖切换而改变。
所以，在AndroidManifest.xml里设置的MiniSdkVersion和 TargetSdkVersion属性大于等于13的情况下，如果你想阻止程序在运行时重新加载Activity，除了设置"orientation"，还必须设置"ScreenSize"。

如果不想让屏幕发生旋转怎么办呢?

指定属性:

android:screenOrientation="portrait"或android:screenOrientation="landscape"

如果<activity>配置了android:screenOrientation属性，则会使android:configChanges="orientation"失效

测试代码中也增加了onSaveInstanceState方法的测试，但是发现Activity即将被销毁的时候并没有执行这个方法，这是为什么呢?

当Activity只执行onPause方法时（Activity a打开一个透明Activity b）这时候如果App设置的targetVersion大于android3.0则不会执行onSaveInstanceState方法。

以上测试结果已经可以说明常见的调用情况了，大家看着测试数据多体会多测试。

三、测试代码
AndroidManifest.xml中用到的关键代码

<uses-permission android:name="android.permission.CALL_PHONE"/>
<uses-permission android:name="android.permission.CHANGE_CONFIGURATIONS"/>
....
<activity android:name=".main.activity.ActivityLifeActivity">
</activity>

<!--如果指定了android:screenOrientation="landscape"这个属性，则屏幕不会发生旋转-->
<activity android:name=".main.activity.SecondDemoActivity" android:configChanges="orientation|screenSize" >
</activity>

主测试界面布局文件activity_life.xml

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

    <Button
        android:id="@+id/id_btn_jump"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="模拟界面跳转"/>
    <Button
        android:id="@+id/id_btn_toast"
        android:textAllCaps="false"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="弹出Toast提示"/>
    <Button
        android:id="@+id/id_btn_dialog"
        android:textAllCaps="false"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="弹出对话框提示"/>
    <Button
        android:id="@+id/id_btn_home"
        android:textAllCaps="false"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="模拟跳到主屏幕界面"/>
    <Button
        android:id="@+id/id_btn_call"
        android:textAllCaps="false"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="模拟打电话"/>

</LinearLayout>

主界面代码:

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.res.Configuration;
import android.net.Uri;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.mobile.cdtx.blog.R;

//测试Activity的生命周期
public class ActivityLifeActivity extends AppCompatActivity implements View.OnClickListener {
    private static final String TAG = "ActivityLifeActivity";
    private Button btnJump, btnToast, btnDialog, btnHome, btnCall;
    Intent intent;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate: ");
        setContentView(R.layout.activity_life);
        initView();
    }

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

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

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

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

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

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

    @Override
    public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
        super.onSaveInstanceState(outState, outPersistentState);
        Log.d(TAG, "onSaveInstanceState: ");
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        Log.d(TAG, "onRestoreInstanceState: ");
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        Log.d(TAG, "onWindowFocusChanged: ");
    }

    //当指定了android:configChanges="orientation"后,方向改变时onConfigurationChanged被调用
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        Log.d(TAG, "onConfigurationChanged:");
    }

    //控件初始化
    private void initView() {
        btnJump = (Button) findViewById(R.id.id_btn_jump);
        btnJump.setOnClickListener(this);
        btnToast = (Button) findViewById(R.id.id_btn_toast);
        btnToast.setOnClickListener(this);
        btnDialog = (Button) findViewById(R.id.id_btn_dialog);
        btnDialog.setOnClickListener(this);
        btnHome = (Button) findViewById(R.id.id_btn_home);
        btnHome.setOnClickListener(this);
        btnCall = (Button) findViewById(R.id.id_btn_call);
        btnCall.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.id_btn_jump:
                startActivity(new Intent(ActivityLifeActivity.this, SecondDemoActivity.class));
                break;
            case R.id.id_btn_toast:
                Toast.makeText(this, "测试Toast", Toast.LENGTH_SHORT).show();
                break;
            case R.id.id_btn_dialog:
                new AlertDialog.Builder(this)
                        .setTitle("标题")
                        .setMessage("简单消息框")
                        .setPositiveButton("确定", null)
                        .show();
                break;
            case R.id.id_btn_home:
                Intent MyIntent = new Intent(Intent.ACTION_MAIN);
                MyIntent.addCategory(Intent.CATEGORY_HOME);
                startActivity(MyIntent);
                break;
            case R.id.id_btn_call:
                intent = new Intent(Intent.ACTION_CALL);
                Uri data = Uri.parse("tel:1234567890");
                intent.setData(data);
                if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(ActivityLifeActivity.this, new String[] {Manifest.permission.CALL_PHONE},1);
                    return;
                }else{
                    startActivity(intent);
                }
                break;
            default:
                break;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == 1) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                intent = new Intent(Intent.ACTION_CALL);
                Uri data = Uri.parse("tel:1234567890");
                intent.setData(data);
                startActivity(intent);
            } else {
                Toast.makeText(this, "权限被拒绝", Toast.LENGTH_SHORT).show();
            }
            return;
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

运行效果图:

模拟界面跳转的界面的布局文件:

activity_second_demo.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_second_demo"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</RelativeLayout>

布局很简单什么控件都没，主要是在代码中打印关键方法。

模拟界面跳转的界面的代码:

import android.content.res.Configuration;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import com.mobile.cdtx.blog.R;

public class SecondDemoActivity extends AppCompatActivity {
    private static final String TAG = "SecondDemoActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate: ");
        setContentView(R.layout.activity_second_demo);
    }

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

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

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

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

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

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

    @Override
    public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
        super.onSaveInstanceState(outState, outPersistentState);
        Log.d(TAG, "onSaveInstanceState: ");
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        Log.d(TAG, "onRestoreInstanceState: ");
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        Log.d(TAG, "onWindowFocusChanged: ");
    }

    //当指定了android:configChanges="orientation"后,方向改变时onConfigurationChanged被调用
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        if(this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE)
        {
            Log.d(TAG, "onConfigurationChanged:横屏");// 获取横屏
        } else if(this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
        {// 获取竖屏
            Log.d(TAG, "onConfigurationChanged:竖屏");// 获取横屏
        }
    }
}

安卓-Activity生命周期

Wireshark 安装+使用（一）

React Native實現二維碼管理界面

React Native自定義帶返回按鈕的標題欄組件

安卓-封裝實用的Toast工具類

安卓-ListActivity的使用

還原AndroidManifest.xml明文的方法

Mac下配置sublime實現LaTeX

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

linux以太網驅動總結