（二）Activity启动模式
启动模式
一、概念
顾名思义，就是activity的启动方式方法，共有4种模式standard，singleTop，singleTask，singleInstance。
为什么要学习启动模式呢？因为有些时候我们是需要控制activity的实例数量的，比如通话界面，整个手机中应该只有一个通话activity的实例。再比如浏览器，我们可以打开多个页面，各个页面间相互独立。这类的需求我们就需要使用启动模式来实现，所以理解每一种启动模式的特点就很必要了。
这里插一句，配置activity启动模式有2种方式，在AndroidManifinest.xml中配置和代码配置
接下来就以一个demo为例说明下几种方式的特点
二、demo相关
2.1 xml布局
2.2 AndroidManifinest.xml
4个Activity，分别配置4种启动模式
2.3 Activity，共有4个Activity，做的事情都是一样的，这里就只贴出一个，其他的类似
package com.example.hjw.launchmode;
import android.content.Intent;
import android.os.PersistableBundle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class MainActivity extends AppCompatActivity {
public static String TAG = "hjw";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG,"onCreate: "+getClass().getSimpleName() + " TaskId: " + getTaskId() + " hasCode:" + this.hashCode());
findViewById(R.id.bt_singleInstance).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, InstanceActivity.class);
startActivity(intent);
}
});
findViewById(R.id.bt_singleTop).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, TopActivity.class);
startActivity(intent);
}
});
findViewById(R.id.bt_singleTask).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, TaskActivity.class);
startActivity(intent);
}
});
findViewById(R.id.bt_self).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, MainActivity.class);
startActivity(intent);
}
});
}
@Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
Log.d(TAG,"onCreate: "+getClass().getSimpleName() + " TaskId: " + getTaskId() + " hasCode:" + this.hashCode());
}
}
好了，准备工作做完了，接下来就进入高潮了
三、4种启动模式
1，standard
如果没有指定启动模式，默认就是这种方式，例子中就是点击self按钮，启动自己，看下log
Line 10264: 01-17 19:28:27.290 D/hjw ( 5419): onCreate: MainActivity TaskId: 426 hasCode:148911758
Line 10321: 01-17 19:28:32.445 D/hjw ( 5419): onCreate: MainActivity TaskId: 426 hasCode:91877479
Line 10344: 01-17 19:28:33.651 D/hjw ( 5419): onCreate: MainActivity TaskId: 426 hasCode:81065124
Line 10366: 01-17 19:28:34.566 D/hjw ( 5419): onCreate: MainActivity TaskId: 426 hasCode:1381727652，singleTop
（1）这次的顺序是先启动MainActivity，然后一直启动singleTopActivity，看下log
Line 9896: 01-17 19:32:46.760 D/hjw ( 5419): onCreate: MainActivity TaskId: 427 hasCode:56325801
Line 12280: 01-17 19:32:49.569 D/hjw ( 5419): onCreate: TopActivity TaskId: 427 hasCode:90947310
Line 12772: 01-17 19:32:51.491 D/hjw ( 5419): onNewIntent: TopActivity TaskId: 427 hasCode:90947310
Line 12780: 01-17 19:32:54.239 D/hjw ( 5419): onNewIntent: TopActivity TaskId: 427 hasCode:90947310
Line 12784: 01-17 19:32:54.381 D/hjw ( 5419): onNewIntent: TopActivity TaskId: 427 hasCode:90947310
（2）这次的顺序是，从MainActivity，启动singleTopActivity，再启动Main，再启动几次Top
Line 9912: 01-17 19:37:32.003 D/hjw ( 5817): onCreate: MainActivity TaskId: 429 hasCode:148911758
Line 10043: 01-17 19:38:06.624 D/hjw ( 5817): onCreate: TopActivity TaskId: 429 hasCode:47509012
Line 10086: 01-17 19:38:08.290 D/hjw ( 5817): onCreate: MainActivity TaskId: 429 hasCode:59946807
Line 10114: 01-17 19:38:11.327 D/hjw ( 5817): onCreate: TopActivity TaskId: 429 hasCode:209995572
Line 10128: 01-17 19:38:12.309 D/hjw ( 5817): onNewIntent: TopActivity TaskId: 429 hasCode:209995572
Line 10135: 01-17 19:38:13.131 D/hjw ( 5817): onNewIntent: TopActivity TaskId: 429 hasCode:209995572
Line 10151: 01-17 19:38:13.863 D/hjw ( 5817): onNewIntent: TopActivity TaskId: 429 hasCode:2099955723，singleTask
测试顺序采用与singleTop同样的方式
（1）
Line 10253: 01-17 19:41:25.604 D/hjw ( 5817): onCreate: MainActivity TaskId: 430 hasCode:202738547
Line 13098: 01-17 19:41:28.461 D/hjw ( 5817): onCreate: TaskActivity TaskId: 431 hasCode:19651321
Line 13132: 01-17 19:41:30.322 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 431 hasCode:19651321
Line 13140: 01-17 19:41:30.900 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 431 hasCode:19651321
Line 13148: 01-17 19:41:31.368 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 431 hasCode:19651321
Line 13156: 01-17 19:41:31.835 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 431 hasCode:19651321
Line 13164: 01-17 19:41:32.305 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 431 hasCode:19651321
（2）
Line 10253: 01-17 19:43:59.360 D/hjw ( 5817): onCreate: MainActivity TaskId: 432 hasCode:57364092
Line 10286: 01-17 19:44:03.450 D/hjw ( 5817): onCreate: TaskActivity TaskId: 433 hasCode:131192636
Line 10333: 01-17 19:44:06.559 D/hjw ( 5817): onCreate: MainActivity TaskId: 433 hasCode:157377881
Line 10358: 01-17 19:44:07.885 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 433 hasCode:131192636
Line 10385: 01-17 19:44:08.989 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 433 hasCode:131192636
Line 10393: 01-17 19:44:09.759 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 433 hasCode:131192636
Line 10401: 01-17 19:44:10.296 D/hjw ( 5817): onNewIntent: TaskActivity TaskId: 433 hasCode:131192636
结论：栈内复用，并且会把它之上的activity实例销毁。从现象看就是back两次，栈就空了。当然了还有其他证明方式
adb shell dumpsys activity activities
4，singleInstance
（1）
Line 10590: 01-17 19:49:49.377 D/hjw ( 5817): onCreate: MainActivity TaskId: 434 hasCode:23450184
Line 10616: 01-17 19:49:51.074 D/hjw ( 5817): onCreate: InstanceActivity TaskId: 435 hasCode:177643169
Line 10633: 01-17 19:49:52.268 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 435 hasCode:177643169
Line 10641: 01-17 19:49:52.489 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 435 hasCode:177643169
Line 10649: 01-17 19:49:52.759 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 435 hasCode:177643169
（2）
Line 10170: 01-17 19:52:58.799 D/hjw ( 5817): onCreate: MainActivity TaskId: 436 hasCode:119769668
Line 10213: 01-17 19:53:01.271 D/hjw ( 5817): onCreate: InstanceActivity TaskId: 437 hasCode:94725757
Line 10238: 01-17 19:53:03.052 D/hjw ( 5817): onCreate: MainActivity TaskId: 436 hasCode:91870454
Line 10293: 01-17 19:53:05.881 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 437 hasCode:94725757
Line 10307: 01-17 19:53:08.611 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 437 hasCode:94725757
Line 10325: 01-17 19:53:09.233 D/hjw ( 5817): onNewIntent: InstanceActivity TaskId: 437 hasCode:94725757至此，4种启动模式的特点就介绍完了。
还有一个遗留的问题，TaskId，就是指任务栈的编号可以通过在AndroidManifinest.xml中给Activity设置taskAffinity属性。
activity在启动的时候会优先寻找自己指定的TaskId，对于前2种启动方式，这个属性并不生效，后两种，是有效的。至于为啥，没研究过，请大神指点。另外我自己还有一个问题
Line 10443: 01-17 19:58:51.761 D/hjw ( 5817): onCreate: MainActivity TaskId: 438 hasCode:6413022
Line 10467: 01-17 19:58:54.475 D/hjw ( 5817): onCreate: TopActivity TaskId: 438 hasCode:6067614
Line 10495: 01-17 19:58:56.345 D/hjw ( 5817): onCreate: InstanceActivity TaskId: 439 hasCode:222214387
Line 10530: 01-17 19:58:57.975 D/hjw ( 5817): onCreate: TopActivity TaskId: 440 hasCode:180213716
Line 10548: 01-17 19:58:59.457 D/hjw ( 5817): onNewIntent: TopActivity TaskId: 440 hasCode:180213716