前言

本文档记录了在 Android 11 平台上，通过修改 Framework 层代码来优化开机体验的实现方案。主要目的是在开机阶段屏蔽默认的“系统启动中”或“Android 正在启动”等提示界面（FallbackHome），延长开机动画的显示时间，直到真正的桌面（Launcher）绘制完成后才退出开机动画，从而实现开机到桌面的无缝衔接。

1. 延迟退出开机动画，等待 Launcher 绘制完成

文件路径：frameworks/base/services/core/java/com/android/server/wm/ActivityRecord.java

修改说明：在 onWindowsDrawn 方法的末尾添加逻辑，当检测到绘制完成的窗口是真正的 Launcher（排除 FallbackHome）时，才通知系统和 SurfaceFlinger 结束开机动画。

代码修改：

在 onWindowsDrawn 方法的最后面补充以下代码：

/** Called when the windows associated app window container are drawn. */
private void onWindowsDrawn(long timestampNs) {
    final TransitionInfoSnapshot info = mTaskSupervisor
            .getActivityMetricsLogger().notifyWindowsDrawn(this, timestampNs);
    final boolean validInfo = info != null;
    final int windowsDrawnDelayMs = validInfo ? info.windowsDrawnDelayMs : INVALID_DELAY;
    final @WaitResult.LaunchState int launchState =
            validInfo ? info.getLaunchState() : WaitResult.LAUNCH_STATE_UNKNOWN;
    // The activity may have been requested to be invisible (another activity has been launched)
    // so there is no valid info. But if it is the current top activity (e.g. sleeping), the
    // invalid state is still reported to make sure the waiting result is notified.
    if (validInfo || this == getDisplayArea().topRunningActivity()) {
        mTaskSupervisor.reportActivityLaunched(false /* timeout */, this,
                windowsDrawnDelayMs, launchState);
    }
    finishLaunchTickingLocked();
    if (task != null) {
        task.setHasBeenVisible(true);
    }

    // --- 新增代码开始 ---
    // 说明：解锁后退出开机动画（等待真正的 Home 绘制完成）
    if (isHomeIntent(intent) && shortComponentName != null && !shortComponentName.contains("FallbackHome")) {
        SystemProperties.set("service.bootanim.exit", "1");
        android.util.Log.e("ActivityRecord", "real home....." + shortComponentName);

        try {
            IBinder surfaceFlinger = ServiceManager.getService("SurfaceFlinger");
            if (surfaceFlinger != null) {
                Slog.i(TAG_WM, "******* TELLING SURFACE FLINGER WE ARE BOOTED!");
                Parcel data = Parcel.obtain();
                data.writeInterfaceToken("android.ui.ISurfaceComposer");
                surfaceFlinger.transact(IBinder.FIRST_CALL_TRANSACTION, // BOOT_FINISHED
                        data, null, 0);
                data.recycle();
            }
        } catch (RemoteException ex) {
            Slog.e(TAG, "Boot completed: SurfaceFlinger is dead!");
        }
    }
    // --- 新增代码结束 ---
}

2. 移除原有的开机动画退出逻辑

文件路径：frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

修改说明：去除了 performEnableScreen 方法中原有的结束开机动画相关代码（主要是注释掉对 SurfaceFlinger 的 BOOT_FINISHED 通知以及设置属性的逻辑）。因为我们已经在步骤 1 中将其延后到了 Launcher 首次绘制完成后执行。

代码修改：

在 performEnableScreen 方法中，找到并完全注释掉以下代码片段：

// Don't enable the screen until all existing windows have been drawn.
if (!mForceDisplayEnabled) {
    // ... 省略部分原有代码
}

/* --- 注释掉以下原生逻辑（此部分逻辑已移至 ActivityRecord 处理） ---
if (!mBootAnimationStopped) {
    Trace.asyncTraceBegin(TRACE_TAG_WINDOW_MANAGER, "Stop bootanim", 0);
    // stop boot animation
    // formerly we would just kill the process, but we now ask it to exit so it
    // can choose where to stop the animation.
    SystemProperties.set("service.bootanim.exit", "1");
    mBootAnimationStopped = true;
}

if (!mForceDisplayEnabled && !checkBootAnimationCompleteLocked()) {
    ProtoLog.i(WM_DEBUG_BOOT, "performEnableScreen: Waiting for anim complete");
    return;
}

try {
    IBinder surfaceFlinger = ServiceManager.getService("SurfaceFlinger");
    if (surfaceFlinger != null) {
        ProtoLog.i(WM_ERROR, "******* TELLING SURFACE FLINGER WE ARE BOOTED!");
        Parcel data = Parcel.obtain();
        data.writeInterfaceToken("android.ui.ISurfaceComposer");
        surfaceFlinger.transact(IBinder.FIRST_CALL_TRANSACTION, // BOOT_FINISHED
                data, null, 0);
        data.recycle();
    }
} catch (RemoteException ex) {
    ProtoLog.e(WM_ERROR, "Boot completed: SurfaceFlinger is dead!");
}
--- 注释结束 --- */

3. 屏蔽 FallbackHome (系统启动中界面)

文件路径：packages/apps/Settings/src/com/android/settings/FallbackHome.java

修改说明：注释掉 mProgressTimeoutRunnable 线程中显示 “系统启动中（FallbackHome）” 界面的 View 动画逻辑，避免在开机底层准备阶段以及等待 Launcher 加载的过程中闪现该过渡视图。

代码修改：

在 FallbackHome.java 类中找到 mProgressTimeoutRunnable，并按如下方式注释掉相关的界面加载代码：

private final Runnable mProgressTimeoutRunnable = () -> {
    /* --- 注释掉加载过渡界面的代码 ---
    View v = getLayoutInflater().inflate(
            R.layout.fallback_home_finishing_boot, null);
    setContentView(v);
    v.setAlpha(0f);
    v.animate()
            .alpha(1f)
            .setDuration(500)
            .setInterpolator(AnimationUtils.loadInterpolator(
                    this, android.R.interpolator.fast_out_slow_in))
            .start();
    --- 注释结束 --- */
    
    getWindow().addFlags(LayoutParams.FLAG_KEEP_SCREEN_ON);
};

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