Android|Android Activity的生命周期与启动模式全面解读 AndroidActivity的生命周期与启动

Activity概述
Activity生命周期

生命周期的调用顺序
演示

Activity的启动模式

启动模式的设置
standard（默认standard）
singleTop
singleTask
singleInstance

Activity概述 ? Activity（活动）是Android应用程序中最基本的组成单位。
? Activity主要负责创建显示窗口，一个Activity对象通常就代表了一个单独的屏幕。
? Activity是用户唯一可以看得到的组件，用来与用户进行交互的。
? Activity是通过一个Activity栈来进行管理，当前显示的Activity被放到栈顶。

Activity生命周期

文章图片

生命周期的调用顺序

文章图片

一、启动activity，然后按返回键退出。
onCreate()->onStart()->onResume()
onPause()->onStop()->onDestory()
二、启动activity，按Home键显示桌面，再点程序图标进入应用程序。
onCreate()->onStart()->onResume()
onPause()->onStop()
onRestart()->onStart()->onResume()
三、启动activityA,再启动activityB
AonCreate()->AonStart()->AonResume()
AonPause()
BonCreate()->BonStart()->BonResume()

演示

package com.qingsu.yingguday06; import androidx.appcompat.app.AppCompatActivity; import android.content.ComponentName; import android.content.Intent; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; public class MainActivity extends AppCompatActivity implements View.OnClickListener {privateButton mBtIntent,mBtIntentOne,mBtIntentTwo,mBtIntentThree; @Overrideprotected void onCreate(Bundle savedInstanceState) {Log.d("TAG","onCreate"); super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); mBtIntent.setOnClickListener(this); }privatevoid initView(){mBtIntent = findViewById(R.id.bt_intentmain); }@Overrideprotected void onStart() {Log.d("TAG","onStart"); super.onStart(); }@Overrideprotected void onResume() {Log.d("TAG","onResume"); super.onResume(); }@Overrideprotected void onPause() {Log.d("TAG","onPause"); super.onPause(); }@Overrideprotected void onStop() {Log.d("TAG","onStop"); super.onStop(); }@Overrideprotected void onRestart() {Log.d("TAG","onRestart"); super.onRestart(); }@Overrideprotected void onDestroy() {Log.d("TAG","onDestroy"); super.onDestroy(); }@Overridepublic void onClick(View v) {switch (v.getId()){case R.id.bt_intentmain:startActivity(intent); ; break; default:break; }}}

package com.qingsu.yingguday06; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; public class HomeActivity extends AppCompatActivity {Button mBtHome,mBtIntentB; @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState); Log.d("TAG","BonCreate"); setContentView(R.layout.activity_home); setTitle("页面B"); mBtHome = findViewById(R.id.bt_intenthome); mBtIntentB = findViewById(R.id.bt_intentB); mBtHome.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent intent = new Intent(HomeActivity.this,MainActivity.class); startActivity(intent); }}); mBtIntentB.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent intent = new Intent(HomeActivity.this,HomeActivity.class); startActivity(intent); }}); }@Overrideprotected void onStart() {Log.d("TAG","BonStart"); super.onStart(); }@Overrideprotected void onResume() {Log.d("TAG","BonResume"); super.onResume(); }@Overrideprotected void onPause() {Log.d("TAG","BonPause"); super.onPause(); }@Overrideprotected void onStop() {Log.d("TAG","BonStop"); super.onStop(); }@Overrideprotected void onRestart() {Log.d("TAG","BonRestart"); super.onRestart(); }@Overrideprotected void onDestroy() {Log.d("TAG","onDestroy"); super.onDestroy(); }}

Activity的启动模式 standard（默认standard）、singleTop、singleTask、singleInstance

启动模式的设置
清单文件中在活动声明中加入launchMode属性默认为standard方式