在開發中，有些方案需要讓螢幕永不休眠，有兩種方法可以去設定，

第一種方法直接改frameworks/base/packages/SettingsProvider/res/values/defaults.xml

<integer name="def_screen_off_timeout">2147483647</integer> 這個值是通過原始碼分析打印出來的。

第二種方法：設定<integer name="def_screen_off_timeout">-1</integer>

修改packages/apps/Settings/src/com/android/settings/DisplaySettings.java

    private void updateTimeoutPreferenceDescription(long currentTimeout) {
        ListPreference preference = mScreenTimeoutPreference;
        String summary;
        if (currentTimeout < 0) {
            // Unsupported value
            //add start.
            final CharSequence[] values = preference.getEntryValues();
            int best = (values.length - 1);
            summary = entries[best].toString();
            //add end.
        } else {
            final CharSequence[] entries = preference.getEntries();
            final CharSequence[] values = preference.getEntryValues();
            if (entries == null || entries.length == 0) {
                summary = "";
            } else {
                int best = 0;
                for (int i = 0; i < values.length; i++) {
                    long timeout = Long.parseLong(values[i].toString());
                    if (currentTimeout >= timeout) {
                        best = i;
                    }
                }
                if (currentTimeout == Integer.MAX_VALUE)
                    summary = entries[best].toString();
                else
                    summary = preference.getContext().getString(R.string.screen_timeout_summary,
                            entries[best]);
            }
        }
        preference.setSummary(summary);
    }