简单介绍Activity生命周期经常调用的几个方法：

onCreate()与onDestroy()

Activity的创建与销毁，处于Activity的entire lifetime完整生命周期

onStart()与onStop()

Activity的可见与不可见，处于Activity的visible lifetime可见生命周期

onResume()与onPause()

Activity的获取焦点与失去焦点,处于Activity的foreground time 前台生命周期

onSaveInstanceState()与onRestoreIntanceState()

保存数据和取出保存的数据，横竖屏切换的时候，两个方法会被同时调用，当然这只是这两个方法同时出现场景之一

onConfiguration()

在Activity的Manifest文件下配置完configChanges属性,如果是横竖屏切换相关值，则在横竖屏切换时会被调用

下面用Activity的使用的七个场景来这些生命周期方法的执行顺序

一、Activity1首次启动

onCreate-->onStart-->onResume

控制台打印效果图

Activity首次启动生命周期调用顺序.png

二、Activity1按返回键并从手机缓存应用列表中启动

onResume-->onPause-->onStop-->onDestroy

再次启动：onCreate-->onStart-->onResume

控制台打印效果图

Activity从手机缓存启动.jpg

三、Activity1按住home键从手机缓存应用列表中再次启动

onResume-->onPause-->onSaveInstanceState-->onStop

再次启动:onRestart-->onStart-->onResume

控制台打印效果图

Home键再从手机缓存启动.jpg

四、Activity1锁屏关闭再开启

onResume-->onPause-->onSaveInstanceState-->onStop

再次启动:onRestart-->onStart-->onResume

控制台打印效果图

锁屏关闭.jpg

五、Activity1启动Activity2

Activity1:onResume-->onPause

Activity2:onCreate-->onStart-->onResume

Activity1:onSaveInstanceState-->onStop

控制台打印效果图

Activity1启动Activity2.jpg

六、Activity1启动Activity2,Activity2退出或者按返回键

Activity2:onResume-->onPause

Activity1:onRestart-->onStart-->onResume

Activity2:onStop-->onDestroy

控制台打印效果图

Activity2被关闭.jpg

七、Activity1横纵屏切换，并做相关配置

竖屏：onCreate-->onStart-->onResume-->onPause-->onSaveInstanceState

-->onStop-->onDestroy

横屏：onCreate-->onStart-->onRestoreInstanceState-->onResume

控制台打印效果图

横纵屏切换.jpg

配置Activity横竖切换不重新创建

android:configChanges="orientation|screenSize"

是在AndroidManifest.xml相应的标签的属性

控制台打印效果图

配置ActivityconfigChanges后生命周期.jpg

Activity1代码块

public class MainActivity extends AppCompatActivity {

static String TAG="dayng";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

if(savedInstanceState!=null){

Log.i(TAG,"退出时保存的数据"+savedInstanceState.getString("dayang"));

}

Log.i(TAG,"-------MainActivity.onCreate--------");

}

public void onClick(View view){

Intent intent=new Intent(this,Main2Activity.class);

startActivity(intent);

}

@Override

protected void onStart() {

super.onStart();

Log.i(TAG,"-------MainActivity.onStart--------");

}

@Override

protected void onResume() {

super.onResume();

Log.i(TAG,"-------MainActivity.onResume--------");

}

@Override

protected void onPause() {

super.onPause();

Log.i(TAG,"-------MainActivity.onPause--------");

}

@Override

protected void onRestart() {

super.onRestart();

Log.i(TAG,"-------MainActivity.onRestart--------");

}

@Override

protected void onStop() {

super.onStop();

Log.i(TAG,"-------MainActivity.onStop--------");

}

@Override

protected void onDestroy() {

super.onDestroy();

Log.i(TAG,"-------MainActivity.onDestroy--------");

}

@Override

protected void onSaveInstanceState(Bundle outState) {

outState.putString("dayang","-----7777777");

super.onSaveInstanceState(outState);

Log.i(TAG,"--------MainActivity.onSaveInstanceState--------");

}

@Override

protected void onRestoreInstanceState(Bundle savedInstanceState) {

super.onRestoreInstanceState(savedInstanceState);

Log.i(TAG,"--------MainActivity.onRestoreInstanceState--------");

}

@Override

public void onConfigurationChanged(Configuration newConfig) {

super.onConfigurationChanged(newConfig);

Log.i(TAG,"--------MainActivity.onConfiguration--------");

}

}

Activity2代码块

public class Main2Activity extends AppCompatActivity {

static String TAG="dayang";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main2);

Log.i(TAG,"-------Main2Activity.onCreate-------");

}

@Override

protected void onStart() {

super.onStart();

Log.i(TAG,"-------Main2Activity.onStart-------");

}

@Override

protected void onResume() {

super.onResume();

Log.i(TAG,"-------Main2Activity.onResume-------");

}

@Override

protected void onPause() {

super.onPause();

Log.i(TAG,"-------Main2Activity.onPause-------");

}

@Override

protected void onStop() {

super.onStop();

Log.i(TAG,"-------Main2Activity.onStop-------");

}

@Override

protected void onRestart() {

super.onRestart();

Log.i(TAG,"-------Main2Activity.onRestart-------");

}

@Override

protected void onDestroy() {

super.onDestroy();

Log.i(TAG,"-------Main2Activity.onDestroy-------");

}

public void close(View view){

finish();

}

@Override

protected void onSaveInstanceState(Bundle outState) {

super.onSaveInstanceState(outState);

Log.i(TAG,"-------Main2Activity.onSaveInstanceState-------");

}

@Override

protected void onRestoreInstanceState(Bundle savedInstanceState) {

super.onRestoreInstanceState(savedInstanceState);

Log.i(TAG,"-------Main2Activity.onRestoreInstanceState-------");

}

@Override

public void onConfigurationChanged(Configuration newConfig) {

super.onConfigurationChanged(newConfig);

Log.i(TAG,"-------Main2Activity.onConfiguration-------");

}

}