经常听到大家讨论类似的需求，怀疑大厂是不是用了此方案，据我个人了解，多数头部 app 其实都是发版来更新节假日的 icon。当然本方案也是一种可选的方案，以前我也调研过，存在问题和作者所述差不多，此外原文链接作者也回复了很多疑问，可以同时了解。

效果图

产品需求

市面上很多App能根据特定活动，动态切换应用图标达到宣传目的，例如淘宝双十一，国庆节等等。那么我们怎样才能在不发新版本的情况下，动态切换应用图标呢？

具体方案

1.图标更换：在AndroidManifest设置应用入口Activity的别名，然后通过setComponentEnabledSetting动态启用或禁用别名进行图标切换。

2.控制图标显示：冷启动App时，调用接口判断是否需要切换icon。

3.触发时机：监听App前后台切换，当App处于后台时切换图标，使得用户无感知。

代码实现

在AndroidManifest.xml中给入口Activity设置activity-alias

<application
    android:name=".MyApplication"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/Theme.SwitchIcon">

    <!-- 原MainActivity -->
    <activity android:name=".MainActivity" />

    <!-- 固定设置一个默认的别名，用来替代原MainActivity -->
    <activity-alias
        android:name=".DefaultAliasActivity"
        android:enabled="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:targetActivity=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity-alias>


    <!-- 别名1，特定活动需要的图标如：双11，国庆节等 -->
    <activity-alias
        android:name=".Alias1Activity"
        android:enabled="false"
        android:icon="@mipmap/ic_launcher_show"
        android:label="@string/app_name"
        android:targetActivity=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</application>

activity-alias标签中的属性如下：

标签	作用
android:name	别名，命名规则同Actively
android:enabled	是否启用别名，这里的主要作用的控制显示应用图标
android:icon	应用图标
android:label	应用名
android:targetActivity	必须指向原入口Activity

在MainActivity中，通过启用或禁用别名进行图标切换

/**
 * 设置默认的别名为启动入口
 */
public void setDefaultAlias() {
    PackageManager packageManager = getPackageManager();

    ComponentName name1 = new ComponentName(this, "com.fengfeibiao.switchicon.DefaultAliasActivity");
    packageManager.setComponentEnabledSetting(name1, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);

    ComponentName name2 = new ComponentName(this, "com.fengfeibiao.switchicon.Alias1Activity");
    packageManager.setComponentEnabledSetting(name2, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);
    }

/**
 * 设置别名1为启动入口
 */
public void setAlias1() {
    PackageManager packageManager = getPackageManager();
    ComponentName name1 = new ComponentName(this, "com.fengfeibiao.switchicon.DefaultAliasActivity");
    packageManager.setComponentEnabledSetting(name1, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);

    ComponentName name2 = new ComponentName(this, "com.fengfeibiao.switchicon.Alias1Activity");
    packageManager.setComponentEnabledSetting(name2, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);
}

ForegroundCallbacks监听App前后台切换

/**
 * 监听App前后台切换
 */
public class ForegroundCallbacks implements Application.ActivityLifecycleCallbacks {
    public static final long CHECK_DELAY = 500;
    public static final String TAG = ForegroundCallbacks.class.getName();

    public interface Listener {
        void onForeground();

        void onBackground();
    }

    private static ForegroundCallbacks instance;
    private boolean foreground = false, paused = true;
    private Handler handler = new Handler();
    private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
    private Runnable check;

    public static ForegroundCallbacks init(Application application) {
        if (instance == null) {
            instance = new ForegroundCallbacks();
            application.registerActivityLifecycleCallbacks(instance);
        }
        return instance;
    }

    public static ForegroundCallbacks get(Application application) {
        if (instance == null) {
            init(application);
        }
        return instance;
    }

    public static ForegroundCallbacks get(Context ctx) {
        if (instance == null) {
            Context appCtx = ctx.getApplicationContext();
            if (appCtx instanceof Application) {
                init((Application) appCtx);
            }
            throw new IllegalStateException(
                    "Foreground is not initialised and " +
                            "cannot obtain the Application object");
        }
        return instance;
    }

    public static ForegroundCallbacks get() {
        if (instance == null) {
            throw new IllegalStateException(
                    "Foreground is not initialised - invoke " +
                            "at least once with parameterised init/get");
        }
        return instance;
    }

    public boolean isForeground() {
        return foreground;
    }

    public boolean isBackground() {
        return !foreground;
    }

    public void addListener(Listener listener) {
        listeners.add(listener);
    }

    public void removeListener(Listener listener) {
        listeners.remove(listener);
    }

    @Override
    public void onActivityResumed(Activity activity) {
        paused = false;
        boolean wasBackground = !foreground;
        foreground = true;
        if (check != null)
            handler.removeCallbacks(check);
        if (wasBackground) {
            Log.d(TAG, "went foreground");

            for (Listener l : listeners) {
                try {
                    l.onForeground();


                } catch (Exception exc) {
                    Log.d(TAG, "Listener threw exception!:" + exc.toString());
                }
            }
        } else {
            Log.d(TAG, "still foreground");
        }
    }

    @Override
    public void onActivityPaused(Activity activity) {
        paused = true;
        if (check != null)
            handler.removeCallbacks(check);
        handler.postDelayed(check = new Runnable() {
            @Override
            public void run() {
                if (foreground && paused) {
                    foreground = false;
                    Log.d(TAG, "went background");
                    for (Listener l : listeners) {
                        try {
                            l.onBackground();
                        } catch (Exception exc) {
                            Log.d(TAG, "Listener threw exception!:" + exc.toString());
                        }
                    }
                } else {
                    Log.d(TAG, "still foreground");
                }
            }
        }, CHECK_DELAY);
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
    }

    @Override
    public void onActivityStarted(Activity activity) {
    }

    @Override
    public void onActivityStopped(Activity activity) {
    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
    }
}

需要在Application中调用ForegroundCallbacks.init(this)进行初始化。

在MainActivity中实现ForegroundCallbacks.Listener对App进行监听，当处于后台判断是否切换应用图标

完整的MainActivity代码：

public class MainActivity extends AppCompatActivity implements ForegroundCallbacks.Listener {

    private int position = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //添加app前后台监听
        ForegroundCallbacks.get(this).addListener(this);

        findViewById(R.id.tv_default).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                position = 0;
            }
        });

        findViewById(R.id.tv_alias1).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                position = 1;
            }
        });

    }

    @Override
    protected void onDestroy() {
        // 移除app前后台监听
        ForegroundCallbacks.get(this).removeListener(this);
        super.onDestroy();
    }

    @Override
    public void onForeground() {

    }

    @Override
    public void onBackground() {
        //根据具体业务需求设置切换条件,我公司采用接口控制icon切换
        if (position == 0) {
            setDefaultAlias();
        } else {
            setAlias1();
        }
    }


    /**
     * 设置默认的别名为启动入口
     */
    public void setDefaultAlias() {
        PackageManager packageManager = getPackageManager();

        ComponentName name1 = new ComponentName(this, "com.fengfeibiao.switchicon.DefaultAliasActivity");
        packageManager.setComponentEnabledSetting(name1, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);

        ComponentName name2 = new ComponentName(this, "com.fengfeibiao.switchicon.Alias1Activity");
        packageManager.setComponentEnabledSetting(name2, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);
    }

    /**
     * 设置别名1为启动入口
     */
    public void setAlias1() {
        PackageManager packageManager = getPackageManager();

        ComponentName name1 = new ComponentName(this, "com.fengfeibiao.switchicon.DefaultAliasActivity");
        packageManager.setComponentEnabledSetting(name1, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);

        ComponentName name2 = new ComponentName(this, "com.fengfeibiao.switchicon.Alias1Activity");
        packageManager.setComponentEnabledSetting(name2, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);
    }
}