Activity的启动模式

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一共四种：standard,singleTop,singleTask,singleInstance

standard

默认的启动模式，每当启动一个新的活动，它都会处于栈顶，且每次启动都会创建一个新的实例。

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Log.e("MainActivity",this.toString());        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(MainActivity.this,MainActivity.class);                startActivity(intent);            }        });    }}

log打印信息,创建了新的实例.

01-05 11:01:01.755 9055-9055/com.vcom.test E/MainActivity: com.vcom.test.MainActivity@a62ffc501-05 11:01:05.853 9055-9055/com.vcom.test E/MainActivity: com.vcom.test.MainActivity@1a2b991

singleTop
使用该模式，如果活动已处于栈顶，则不会创建新的实例。如果该活动不处于栈顶再会重新创建实例

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.vcom.test">    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <activity            android:launchMode="singleTop"            android:name=".MainActivity">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>

AndroidManifest.xml添加singleTop

android:launchMode="singleTop

代码还是跟上面的一样。

打印信息：

01-05 11:04:42.876 12981-12981/com.vcom.test E/MainActivity: com.vcom.test.MainActivity@a62ffc5

无论点击多少次，都是只创建一次实例。

singleTask
活动只要还在该栈中，就不会创建新的实例

AndroidManifest.xml添加singleTask

android:launchMode="singleTask"

代码：

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Log.e("MainActivity",this.toString());        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(MainActivity.this,TwoActivity.class);                startActivity(intent);            }        });    }    @Override    protected void onRestart() {        super.onRestart();        Log.e("MainActivity","onRestart");    }}

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class TwoActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_two);        Log.e("TwoActivity",this.toString());        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(TwoActivity.this,MainActivity.class);                startActivity(intent);            }        });    }    @Override    protected void onDestroy() {        super.onDestroy();        Log.e("TwoActivity","onDestroy");    }}

log打印信息：

01-05 11:14:53.636 23822-23822/com.vcom.test E/MainActivity: com.vcom.test.MainActivity@a62ffc501-05 11:14:57.969 23822-23822/com.vcom.test E/TwoActivity: com.vcom.test.TwoActivity@aabcdf501-05 11:15:02.422 23822-23822/com.vcom.test E/MainActivity: onRestart01-05 11:15:02.765 23822-23822/com.vcom.test E/TwoActivity: onDestroy

由TwoActivity跳转到MainActivity，没有创建新的实例，只是执行onRestart方法，而TwoActivity则执行onDestroy方法。

singleInstance
该模式会启动一个新的返回栈来管理活动，即不再同一个栈中。如果活动在栈中不会重新创建新的实例

AndroidManifest.xml添加singleInstance

android:launchMode="singleInstance"

代码：

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Log.e("MainActivity","task id is "+ getTaskId());        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(MainActivity.this,TwoActivity.class);                startActivity(intent);            }        });    }}

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class TwoActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_two);        Log.e("TwoActivity","task id is "+ getTaskId());        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(TwoActivity.this,ThreeActivity.class);                startActivity(intent);            }        });    }}

package com.vcom.test;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class ThreeActivity extends AppCompatActivity {    private Button button;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_three);        Log.e("ThreeActivity","task id is "+ getTaskId());        button = (Button)findViewById(R.id.button);        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(ThreeActivity.this,MainActivity.class);                startActivity(intent);            }        });    }}

log打印信息：

01-05 11:25:08.702 3316-3316/com.vcom.test E/MainActivity: task id is 28201-05 11:25:10.467 3316-3316/com.vcom.test E/TwoActivity: task id is 28301-05 11:25:11.430 3316-3316/com.vcom.test E/ThreeActivity: task id is 283

TwoActivity、ThreeActivity在同一个栈中。

MainActivity在另一栈中

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