完全模仿微信字体设置.md

[johnwatsondev]

行为

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使用 adb shell dumpsys activity activities 命令查看 activities 在任务栈变化，
改进版命令：adb shell dumpsys activity activities | sed -En -e '/Running activities/,/Run #0/p' (多谢前辈 @liuxing917738 指导)

测试机型：Nexus 5 (6.0.1)

Task Stack 变化

Step 1 2 3 4 均为手动添加，方便下文叙述。

Step 1

Running activities (most recent first):
    TaskRecord{45a6662 #208 A=com.tencent.mm U=0 sz=4}
      Run #3: ActivityRecord{c04e6f1 u0 com.tencent.mm/.plugin.setting.ui.setting.SettingsFontUI t208}
      Run #2: ActivityRecord{8fa53ac u0 com.tencent.mm/.plugin.setting.ui.setting.SettingsAboutSystemUI t208}
      Run #1: ActivityRecord{9c0eebd u0 com.tencent.mm/.plugin.setting.ui.setting.SettingsUI t208}
      Run #0: ActivityRecord{d29fc3a u0 com.tencent.mm/.ui.LauncherUI t208}

Step 2

Running activities (most recent first):
    TaskRecord{477c03b #214 A=com.tencent.mm U=0 sz=1}
      Run #2: ActivityRecord{44c7cbe u0 com.tencent.mm/.ui.LauncherUI t214}
    TaskRecord{45a6662 #208 A=com.tencent.mm U=0 sz=2}
      Run #1: ActivityRecord{d29fc3a u0 com.tencent.mm/.ui.LauncherUI t208 f}
      Run #0: ActivityRecord{c04e6f1 u0 com.tencent.mm/.plugin.setting.ui.setting.SettingsFontUI t208 f}

Step 3

Running activities (most recent first):
    TaskRecord{477c03b #214 A=com.tencent.mm U=0 sz=1}
      Run #1: ActivityRecord{44c7cbe u0 com.tencent.mm/.ui.LauncherUI t214}
    TaskRecord{45a6662 #208 A=com.tencent.mm U=0 sz=1}
      Run #0: ActivityRecord{c04e6f1 u0 com.tencent.mm/.plugin.setting.ui.setting.SettingsFontUI t208 f}

Step 4

Running activities (most recent first):
    TaskRecord{477c03b #214 A=com.tencent.mm U=0 sz=1}
      Run #0: ActivityRecord{44c7cbe u0 com.tencent.mm/.ui.LauncherUI t214}

各 Activity 清单文件如下：

<activity android:configChanges="keyboardHidden|orientation|screenSize" android:label="@string/axo" android:launchMode="singleTop" android:name=".ui.LauncherUI" android:theme="@style/iz" android:windowSoftInputMode="adjustResize|stateHidden">
    <intent-filter>
        <action android:name="android.intent.action.MAIN"/>
        <category android:name="android.intent.category.LAUNCHER"/>
        <category android:name="android.intent.category.MULTIWINDOW_LAUNCHER"/>
    </intent-filter>
    <intent-filter>
        <action android:name="com.tencent.mm.action.BIZSHORTCUT"/>
        <category android:name="android.intent.category.
    </intent-filter>
</activity>

<activity android:configChanges="keyboardHidden|orientation|screenSize" android:name=".plugin.setting.ui.setting.SettingsFontUI"/>

<activity android:configChanges="keyboardHidden|orientation|screenSize" android:name=".plugin.setting.ui.setting.SettingsAboutSystemUI"/>

<activity android:configChanges="keyboardHidden|orientation|screenSize" android:name=".plugin.setting.ui.setting.SettingsUI"/>

TL;DR : 各 Activity LaunchMode 如下：

LauncherUI ：singleTop
SettingsFontUI：standand
SettingsAboutSystemUI：standand
SettingsUI：standand

已实现的方案

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在 SettingsFontUI 界面中捕获点击 back 键事件，加入如下代码：

  @Override public void onBackPressed() {
    //super.onBackPressed();

    // Restart SettingsFontUI activity if font scale changed
    Intent i = new Intent(SettingsFontUI.this, LauncherUI.class);
    i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(i);
  }

修改 font scale 代码：

public static void setFontScale(Context context, float scale) {
    Context appContext =   context.getApplicationContext();

    Configuration configuration = appContext.getResources().getConfiguration();

    Configuration newConfiguration = new Configuration();
    newConfiguration.updateFrom(configuration);
    newConfiguration.fontScale = scale;

    DisplayMetrics newMetrics = new DisplayMetrics();
    newMetrics.setToDefaults();

    context.getApplicationContext()
        .getResources()
        .updateConfiguration(newConfiguration, newMetrics);

    // save font scale in SharedPreferences or DB (anywhere you want)
  }

当 LauncherUI 启动时，直接读取 font scale 并在 onCreate 方法中设置即可。

分析

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1. 观察之后发现，从 Step 1 到 2 的变化特别有趣，在 Task 208 中，栈底 Activity 从 LauncherUI 变为 SettingsFontUI，中间的两个界面消失，然后从 Step 2 到 4，LauncherUI 和 SettingsFontUI 依次消失。
2. 新的 LauncherUI 是在新的 Task 214 中出现的。

疑问

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在新 Task 中启动主界面，然后把旧 Task 中 所有 Activity 全部结束，这是如何做到的？