Activity的生命周期

Activity的生命周期

![先看一张经典的生命周期图](http://img.blog.csdn.net/20160610150434651)

• OnCreate()
  
  • 在Activity第一次创建启动时调用
• OnStart()
  
  • 当前的Activity由不可见为成可见时调用，例如按下Home键退出Activity或者当前的Activity被其他Activity彻底覆盖时调用
• OnResume()
  
  • 当前的Activity位于状态，处在运行状态，和用户交互时，所调用
• OnPause()
  
  • 当前的Activity被遮挡住，但仍然为可见状态时,会进入暂停状态，会执行此方法，当遮挡物消失时，会执行OnResume()，再次进入运行状态.
• OnStop()
  -当前的Activity彻底为不可见时，，例如按下home键，会先调用OnPause,在接着调用OnStop进入停止状态。
• OnRestart()
  -当Activity为彻底可见时，就会调用此方法，再调用OnStart,在调用OnResume;
• OnDestroy()
  -当按下OnBack键，就会执行OnDestroy() ，销毁当前Activity

activity_main.xml<LinearLayout     xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <Button        android:id="@+id/btn_Normal"         android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="This a is Dlialog"/>    <Button        android:id="@+id/btn_Dlialog"         android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="This a is Normal"/></LinearLayout>nomal_activity.xml<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent" >    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="this a is nomal activity" /></RelativeLayout>dialog_activity.xml<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent" >    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="this a is dialog activity" /></RelativeLayout>public class MainActivity extends Activity implements OnClickListener{    private Button mBtnNormal,mBtnDliaog;    private static String TAG = "MainActivity";    @Override    protected void onCreate(Bundle savedInstanceState)     {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        if(savedInstanceState!=null)        {            String value = savedInstanceState.getString("strValue");        }        mBtnNormal = (Button) findViewById(R.id.btn_Normal);        mBtnDliaog = (Button) findViewById(R.id.btn_Dlialog);        mBtnNormal.setOnClickListener(this);        mBtnDliaog.setOnClickListener(this);    }    @Override    public void onClick(View v)     {        switch (v.getId())         {        case R.id.btn_Normal:            Intent intent = new Intent(this,NomalActivity.class);            startActivity(intent);            break;        case R.id.btn_Dlialog:            Intent intent2 = new Intent(this,DialogActivty.class);            startActivity(intent2);            //ActivityCollector.Activityfinish();            break;        }    }    @Override    protected void onSaveInstanceState(Bundle outState) {        super.onSaveInstanceState(outState);        String str = "Hellow Android";        outState.putString("strValue", str);    }    @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 onRestart()     {        super.onRestart();        Log.d(TAG, "onRestart()");    }    @Override    protected void onDestroy()     {        super.onDestroy();        Log.d(TAG, "onDestroy()");    }}public class DialogActivty extends Activity{    @Override    protected void onCreate(Bundle savedInstanceState)     {        super.onCreate(savedInstanceState);        setContentView(R.layout.dialog_activity);    }}public class NomalActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState)     {        super.onCreate(savedInstanceState);        setContentView(R.layout.nomal_activity);    }}AndroidManifest.xml<application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name=".MainActivity"            android:label="@string/app_name" >            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>        <activity android:name=".NomalActivity"></activity>        <activity android:name=".DialogActivty" android:theme="@android:style/Theme.Dialog"></activity></application> mBtnNormal     ![点击mBtnNormal](http://img.blog.csdn.net/20160610154919936)     ![按下Back键盘](http://img.blog.csdn.net/20160610155020858) mBtnDliaog     ![点击mBtnDliaog](http://img.blog.csdn.net/20160610155223405)     ![按下Back键盘](http://img.blog.csdn.net/20160610155250374)