往Android7.0的settings的主選單裡新增一條item. N與M的Settings不同,在M上只要找到Settings裡面的相應的佈局新增就好,但在N上由於Setting裡面的item不再受佈局控制,所以得在程式碼中新增.
找到/packages/apps/Settings/src/com/android/settings/SettingsActivity.java
在settingsActivity.java裡面的private void doUpdateTilesList() {}新增程式碼才會顯示在Settings的item裡面,具體如下:

private void doUpdateTilesList
 
() {
//add start
setTileEnabled(new ComponentName(packageName,
Settings.WtkSecurityLockersActivity.class.getName()),getResources().getBoolean(R.bool.show_security_lock), isAdmin, pm);
//add  end
}

這裡添加了這段程式碼之後就可以顯示在settings的item裡面了,具體還有以下的一些完善:在SettingsActivity.java裡面的

private String[] SETTINGS_FOR_RESTRICTED = {
//add  start
 

Settings.WtkSecurityLockersActivity.class.getName(),
//add  end
    };
private static final String[] ENTRY_FRAGMENTS = {
//add  start
WtkSecurityLockers.class.getName(),
//add  end
    };
packages/apps/Settings/src/com/android/settings/Settings.java裡面加
public static class WtkSecurityLockersActivity extends SettingsActivity
 
 { /* empty */ }

packages/apps/Settings/AndroidManifest.xml裡面加:
<!--add  (start)-->
    <!-- A: WtkSecurityLockers Settings -->
        <activity android:name="Settings$WtkSecurityLockersActivity"
                    android:label="@string/security_locker"
                    android:icon="@drawable/ic_wtk_securitylocker">
                <intent-filter android:priority="4">
                    <action android:name="com.android.settings.action.SETTINGS" />
                </intent-filter>
                <meta-data android:name="com.android.settings.category"
                    android:value="com.android.settings.category.system" />
                <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                    android:value="com.android.settings.WtkSecurityLockers" />
                <meta-data android:name="com.android.settings.title"
                           android:resource="@string/security_locker" />
                <meta-data android:name="com.android.settings.icon"
                           android:resource="@drawable/ic_wtk_securitylocker" />
           </activity>
    <!-- A: WtkSecurityLockers Settings -->
    <!--add (end)-->

packages/apps/Settings/src/com/android/settings/下面新增一個類:
package com.android.settings;

import com.android.settings.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.preference.Preference;
import android.support.v7.preference.PreferenceScreen;
import android.support.v14.preference.SwitchPreference;
import android.util.Log;
import android.os.SystemProperties;
import android.provider.Settings;
import com.android.internal.logging.MetricsProto.MetricsEvent;

public class WtkSecurityLockers extends SettingsPreferenceFragment 
            implements Preference.OnPreferenceChangeListener, Preference.OnPreferenceClickListener{

    private static final String KEY_SECURITY_LOCKER = "security_lockers";
    @Override
    public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         Log.e("lcg","KEY_SECURITY_LOCKER = "+KEY_SECURITY_LOCKER);
         Intent intent = new Intent().setClassName("com.wtk.wtksecuritylocker", "com.wtk.wtksecuritylocker.LockerListActivity");
         intent.putExtra(KEY_SECURITY_LOCKER,true);
         startActivity(intent);
         getActivity().finish();
     }
     @Override
     public void onResume() {
     super.onResume();
     }
    @Override
    public boolean onPreferenceClick(Preference preference) {
         // TODO Auto-generated method stub
         return false;
    }
    @Override
    public boolean onPreferenceChange(Preference preference, Object newValue) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean onPreferenceTreeClick(Preference preference) {
        // TODO Auto-generated method stub

        return super.onPreferenceTreeClick(preference);
    }

    @Override
    protected int getMetricsCategory() {
        // TODO Auto-generated method stub
        return  MetricsEvent.DEVICEINFO_STORAGE;
    }
}

至此就可以在Settings裡面的主選單介面新增一個item,點選該item就會進入我們想進的介面.
附上:packages/apps/Settings/src/com/android/settings/SettingsActivity.java

private void setTileEnabled(ComponentName component, boolean enabled, boolean isAdmin,
                                PackageManager pm) {
        if (UserHandle.MU_ENABLED && !isAdmin && getPackageName().equals(component.getPackageName())
                && !ArrayUtils.contains(SETTINGS_FOR_RESTRICTED, component.getClassName())) {
            enabled = false;
        }
        setTileEnabled(component, enabled);
    }
frameworks\base\packages\SettingsLib\src\com\android\settingslib\drawer\SettingsDrawerActivity.java裡面
public void setTileEnabled(ComponentName component, boolean enabled) {
        PackageManager pm = getPackageManager();
        int state = pm.getComponentEnabledSetting(component);
        boolean isEnabled = state == PackageManager.COMPONENT_ENABLED_STATE_ENABLED;
if (isEnabled != enabled || state == PackageManager.COMPONENT_ENABLED_STATE_DEFAULT) {
            if (enabled) {
                sTileBlacklist.remove(component);
            } else {
                sTileBlacklist.add(component);
            }
 pm.setComponentEnabledSetting(component, enabled
                    ? PackageManager.COMPONENT_ENABLED_STATE_ENABLED
                    : PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                    PackageManager.DONT_KILL_APP);
            new CategoriesUpdater().execute();
        }
    }

由此可見往Android7.0的Settingsk裡新增item不需要佈局,至於為什麼,還有待繼續研究.