Activity的四种启动模式-SingleTask和SingleInstance

四种启动模式经常忘记, 在这里用例子记录下.
主要介绍SingleTask 和SingleInstance, 两个Activity用来测试,分别是TaskOne 和 TaskTwo.
TaskOne有两个Activity, 代码如下:

public class ActivityOne extends Activity implements View.OnClickListener{    private static final String TAG = "One +FredCao";    private Button btnOne;    private Context mContext;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_activity_one);        btnOne = (Button)findViewById(R.id.btnOne);        btnOne.setOnClickListener(this);        mContext = this;        Log.d(TAG, "onCreate: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onPause() {        super.onPause();        Log.d(TAG, "onPause: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onDestroy() {        super.onDestroy();        Log.d(TAG, "onDestroy: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onResume() {        super.onResume();        Log.d(TAG, "onResume: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onStart() {        super.onStart();        Log.d(TAG, "onStart: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onStop() {        super.onStop();        Log.d(TAG, "onStop: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    public void onClick(View v) {        switch(v.getId()) {            case R.id.btnOne:                Intent intent = new Intent(this, ActivityTwo.class);                startActivity(intent);        }    }}

ActivityTwo代码一样,都是打印了很多log.

配置文件是这样的,其中ActivityOne的启动模式是singleInstance, ActivityTwo是默认.

<application    android:allowBackup="true"    android:icon="@mipmap/ic_launcher"    android:label="@string/app_name"    android:theme="@style/AppTheme"    >    <activity        android:name=".ActivityOne"        android:label="@string/app_name"        android:launchMode="singleInstance">        <intent-filter>            <action android:name="android.intent.action.MAIN" />            <category android:name="android.intent.category.LAUNCHER" />        </intent-filter>    </activity>    <activity android:name=".ActivityTwo">        <intent-filter>            <action android:name="android.intent.com.fred"/>            <category android:name="android.intent.category.DEFAULT"/>        </intent-filter>    </activity></application>

TaskTwo包含三个Activity, 代码如下:

public class ActivityOne extends Activity implements View.OnClickListener{    private static final String TAG = "1 +FredCao";    private Button btnOne;    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.buttonOne:                Intent intent  = new Intent(this, ActivityTwo.class);                startActivity(intent);                overridePendingTransition(android.R.anim.slide_in_left,android.R.anim.slide_out_right);        }    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btnOne = (Button)findViewById(R.id.buttonOne);        btnOne.setOnClickListener(this);        Log.d(TAG, "onCreate: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onPause() {        super.onPause();        Log.d(TAG, "onPause: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onDestroy() {        super.onDestroy();        Log.d(TAG, "onDestroy: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onResume() {        super.onResume();        Log.d(TAG, "onResume: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onStart() {        super.onStart();        Log.d(TAG, "onStart: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onStop() {        super.onStop();        Log.d(TAG, "onStop: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }    @Override    protected void onNewIntent(Intent intent) {        super.onNewIntent(intent);        Log.d(TAG, "onNewIntent: " + ", taskId is: " + this.getTaskId() + ", processId is: " + android.os.Process.myPid());    }}

配置文件如下, ActivityTwo启动模式是singleTask,其余是默认.

<application    android:allowBackup="true"    android:icon="@mipmap/ic_launcher"    android:label="@string/app_name"    android:theme="@style/AppTheme" >    <activity        android:name=".ActivityOne"        android:label="@string/app_name"        android:alwaysRetainTaskState="true"        >        <intent-filter>            <action android:name="android.intent.action.MAIN" />            <category android:name="android.intent.category.DEFAULT"/>            <category android:name="android.intent.category.LAUNCHER" />        </intent-filter>    </activity>    <activity android:name=".ActivityTwo"        android:launchMode="singleTask">        <intent-filter>            <category android:name="android.intent.category.DEFAULT"/>            <action android:name="com.example.fredwang.tasktwo.LAUNCHER"/>        </intent-filter>    </activity>    <activity android:name=".ActivityThree">        <intent-filter>            <category android:name="android.intent.category.DEFAULT"/>        </intent-filter>    </activity></application>

测试步骤,Launch TaskOne, 然后可以按按钮launch TaskTwo.
Activity的启动步骤如下:

TaskOne中打开Activity的Log 如下, 可以看到,由于ActivityOne的启动模式是SingleInstance, 所以ActivityTwo的Task id和ActivityOne的不一样. 但是进程ID却是一样的,说明两个Activity是运行在同一个Application 的进程中.

03-08 14:41:15.564 D/One +FredCao( 7736): onCreate: , taskId is: 126, processId is: 773603-08 14:41:15.574 D/One +FredCao( 7736): onStart: , taskId is: 126, processId is: 773603-08 14:41:15.594 D/One +FredCao( 7736): onResume: , taskId is: 126, processId is: 773603-08 14:41:19.654 D/One +FredCao( 7736): onPause: , taskId is: 126, processId is: 773603-08 14:41:19.694 D/Two +FredCao( 7736): OnCreate: , taskId is: 130, processId is: 773603-08 14:41:19.704 D/Two +FredCao( 7736): ProcessName: com.example.fredwang.taskone03-08 14:41:19.704 D/Two +FredCao( 7736): onStart: , taskId is: 130, processId is: 773603-08 14:41:19.704 D/Two +FredCao( 7736): onResume: , taskId is: 130, processId is: 773603-08 14:41:20.104 D/One +FredCao( 7736): onStop: , taskId is: 126, processId is: 7736

TaskOne的ActivityTwo打开TaskTwo的ActivityTwo的Log如下,可以看出, Task id 和进程id都不一样.

03-08 14:41:20.854 D/Two +FredCao( 7736): onPause: , taskId is: 130, processId is: 773603-08 14:41:20.984 D/2 +FredCao( 7884): onCreate: , taskId is: 131, processId is: 788403-08 14:41:20.984 D/2 +FredCao( 7884): onCreate: com.example.fredwang.tasktwo.ActivityTwo@22ac054803-08 14:41:20.994 D/2 +FredCao( 7884): onStart: , taskId is: 131, processId is: 788403-08 14:41:20.994 D/2 +FredCao( 7884): onResume: , taskId is: 131, processId is: 788403-08 14:41:21.334 D/Two +FredCao( 7736): onStop: , taskId is: 130, processId is: 7736

TaskTwo自己的Activity互相跳转的Log如下, 可以看出,三个Activity都是在一个Task中, 也在同一个进程中.

03-08 14:41:24.074 D/2 +FredCao( 7884): onPause: , taskId is: 131, processId is: 788403-08 14:41:24.094 D/3 +FredCao( 7884): onCreate: , taskId is: 131, processId is: 788403-08 14:41:24.094 D/3 +FredCao( 7884): onStart: , taskId is: 131, processId is: 788403-08 14:41:24.104 D/3 +FredCao( 7884): onResume: , taskId is: 131, processId is: 788403-08 14:41:24.564 D/2 +FredCao( 7884): onStop: , taskId is: 131, processId is: 788403-08 14:41:26.234 D/3 +FredCao( 7884): onPause: , taskId is: 131, processId is: 788403-08 14:41:26.264 D/1 +FredCao( 7884): onCreate: , taskId is: 131, processId is: 788403-08 14:41:26.264 D/1 +FredCao( 7884): onStart: , taskId is: 131, processId is: 788403-08 14:41:26.264 D/1 +FredCao( 7884): onResume: , taskId is: 131, processId is: 788403-08 14:41:26.714 D/3 +FredCao( 7884): onStop: , taskId is: 131, processId is: 788403-08 14:41:28.274 D/3 +FredCao( 7884): onDestroy: , taskId is: 131, processId is: 788403-08 14:41:28.294 D/1 +FredCao( 7884): onPause: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onNewIntent: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onStart: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onResume: , taskId is: 131, processId is: 788403-08 14:41:28.844 D/1 +FredCao( 7884): onStop: , taskId is: 131, processId is: 788403-08 14:41:28.844 D/1 +FredCao( 7884): onDestroy: , taskId is: 131, processId is: 7884

到目前为止, 可以看出SingelInstance和SingleTask的不同之处, SingleInstace只允许一个Task中只有这一个Activity实例, 除了自己之外也不允许有其他的Activity实例. SingleTask却可以和其他的Activity实例在同一个Task中. 那到死SingleTask有什么用处. 我们看一下按back键的效果.

以下是按back键的log, 可以看出, TaskTwo中的ActivityTwo直接跳转到TaskOne的ActivityTwo了.

03-08 14:57:14.864 D/2 +FredCao( 7884): onPause: , taskId is: 131, processId is: 788403-08 14:57:14.894 D/Two +FredCao( 7736): onStart: , taskId is: 130, processId is: 773603-08 14:57:14.894 D/Two +FredCao( 7736): onResume: , taskId is: 130, processId is: 773603-08 14:57:15.234 D/2 +FredCao( 7884): onStop: , taskId is: 131, processId is: 788403-08 14:57:15.234 D/2 +FredCao( 7884): onDestroy: , taskId is: 131, processId is: 7884

这是为什么呢?仔细看我们的TaskTwo中的Activity跳转的Log. 当我们ActivityOne重新跳转到ActivityTwo中的时候, ActivityThree首先onDestroy. 然后ActivityTwo回调了onNewIntent, 然后ActivityOne也被onDestroy了.

03-08 14:41:28.274 D/3 +FredCao( 7884): onDestroy: , taskId is: 131, processId is: 788403-08 14:41:28.294 D/1 +FredCao( 7884): onPause: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onNewIntent: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onStart: , taskId is: 131, processId is: 788403-08 14:41:28.344 D/2 +FredCao( 7884): onResume: , taskId is: 131, processId is: 788403-08 14:41:28.844 D/1 +FredCao( 7884): onStop: , taskId is: 131, processId is: 788403-08 14:41:28.844 D/1 +FredCao( 7884): onDestroy: , taskId is: 131, processId is: 7884

所以SingleTask的作用是, 当Task已经有了这个Activity之后, 如果后续的操作又重新跳转到相同的Activity, 那么在此Activity之上的所有Activity都会被强制销毁出栈.