Android-Activity lunchmode(SingleTask和SingleInstance)的区别

最新推荐文章于 2020-02-27 18:13:16 发布

benjamin gao

最新推荐文章于 2020-02-27 18:13:16 发布

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分类专栏： activity 文章标签： launchModeSingleTask

本文链接：https://blog.youkuaiyun.com/musk6/article/details/62896821

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本文详细探讨了Android中Activity的launchMode，尤其是SingleTask和SingleInstance模式的区别。当使用SingleTask模式时，如果任务栈中已有目标Activity的实例，所有位于其上方的Activity会被移除销毁，目标Activity成为栈顶并执行onStart和onResume。若需传递Intent参数，需在Activity中重写onNewIntent方法。

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----官方解释点击打开链接

--------- 单独来看launchMode = singleTask

MainActivity的启动模式设置为SingleTask

MainActivity2的启动模式设置为standard

默认启动MainActivity，然后在MainActivity里启动MainActivity2，再在MainActivity2里启动MainActivity，注意观察activity任务栈的情况：

当在MainActivity2里再次启动MainActivity时，MainActivity2被从Activity任务栈顶移除并销毁，而使得MainActivity成为了栈顶实例。

------------ log

03-30 14:30:47.591 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onCreate: 1111111111111111111111
03-30 14:30:47.592 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onStart: 11111111111111111111111111
03-30 14:30:47.592 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onResume: 1111111111111111111111
启动MainActivity2
03-30 14:30:49.250 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onPause: 111111111111111111111111
03-30 14:30:49.279 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onCreate: 2222222222222222222222222
03-30 14:30:49.280 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onStart: 2222222222222222222222222
03-30 14:30:49.283 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onResume: 22222222222222222222222222
03-30 14:30:49.993 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onStop: 1111111111111111111111111
重新启动MainActivity
03-30 14:30:50.713 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onPause: 22222222222222222222222222
03-30 14:30:50.718 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onStart: 11111111111111111111111111
03-30 14:30:50.718 15740-15740/com.adnonstop.activitylifecycler I/MainActivity: onResume: 1111111111111111111111
03-30 14:30:51.307 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onStop: 2222222222222222222222222
03-30 14:30:51.307 15740-15740/com.adnonstop.activitylifecycler I/MainActivity2: onDestroy: 2222222222222222222222222

-------- 由此可以得出结论

launchmode = SingleTask ，

如果任务栈中已经存在Activity A实例，则当再次启动该Activity A时，在任务栈中处于Activity A上的所有Activity都会被从任务栈里移除并销毁，从而实现Activity A位于的栈顶。

Actiivty A 调用的生命周期方法为 onStart,onResume，并不会调用onCreate方法。

如果要传递Intent参数，必须在Activity A里复写onNewIntent(Intent intent )方法获取Intent和Intent参数。

MainActivity

public class MainActivity extends AppCompatActivity {

    private static final String TAG = MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.i(TAG, "onCreate: 1111111111111111111111");
        initView();
    }

    private void initView() {
        Button btnNA = (Button) findViewById(R.id.btn_newac);
        btnNA.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(MainActivity.this, MainActivity2.class));
//                finish();
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart: 11111111111111111111111111");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume: 1111111111111111111111");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause: 111111111111111111111111");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop: 1111111111111111111111111");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy: 11111111111111111111111");
    }
}

MainActivity2

public class MainActivity2 extends AppCompatActivity {

    private static final String TAG = MainActivity2.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        Log.i(TAG, "onCreate: 2222222222222222222222222");
        TextView tvSA = (TextView) findViewById(R.id.tv_startActivity);
        tvSA.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(MainActivity2.this, MainActivity.class));
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart: 2222222222222222222222222");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume: 22222222222222222222222222");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause: 22222222222222222222222222");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop: 2222222222222222222222222");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy: 2222222222222222222222222");
    }
}

清单文件配置

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:launchMode="singleTask">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity2"></activity>
    </application>