设立默认应用

 setDefaultLauncher();

 private void setDefaultLauncher() {
        // get default component
        boolean mFirstLaunch = false;
        String packageName = "com.cyanogenmod.trebuchet";// 默认launcher包名
        String className = "com.cyanogenmod.trebuchet.Launcher";// //默认launcher入口
        Log.d("MyTag", "defautl packageName = " + packageName
                + ", default className = " + className);
        if ((packageName != null && packageName.trim().length() > 1)
                && (className != null && className.trim().length() > 0)) {
            boolean firstLaunch = SystemProperties.getBoolean(
                    "persist.sys.sw.firstLaunch", true); // 只做一次
                                                         // 可以注意这几个变量firstLaunch
                                                         // mFirstLaunch
            Log.d("MyTag", "firstLaunch = " + firstLaunch);
            if (firstLaunch) {
                mFirstLaunch = true;
                // do this only for the first boot
                SystemProperties.set("persist.sys.sw.firstLaunch", "false");
            }
            Log.d("MyTag", "firstLaunch = " + firstLaunch);
            if (true) {
                IPackageManager pm = ActivityThread.getPackageManager();

                // 清除当前默认launcher
                ArrayList<IntentFilter> intentList = new ArrayList<IntentFilter>();
                ArrayList<ComponentName> cnList = new ArrayList<ComponentName>();
                getPackageManager().getPreferredActivities(intentList, cnList,
                        null);
                IntentFilter dhIF;
                for (int i = 0; i < cnList.size(); i++) {
                    dhIF = intentList.get(i);
                    if (dhIF.hasAction(Intent.ACTION_MAIN)
                            && dhIF.hasCategory(Intent.CATEGORY_HOME)) {
                        getPackageManager().clearPackagePreferredActivities(
                                cnList.get(i).getPackageName());
                    }
                }

                // 获取所有launcher activity
                Intent intent = new Intent(Intent.ACTION_MAIN);
                intent.addCategory(Intent.CATEGORY_HOME);
                List<ResolveInfo> list = new ArrayList<ResolveInfo>();
                try {
                    list = pm.queryIntentActivities(intent,
                            intent.resolveTypeIfNeeded(getContentResolver()),
                            PackageManager.MATCH_DEFAULT_ONLY,
                            UserHandle.getCallingUserId());
                } catch (RemoteException e) {
                    throw new RuntimeException("Package manager has died", e);
                }
                // get all components and the best match
                IntentFilter filter = new IntentFilter();
                filter.addAction(Intent.ACTION_MAIN);
                filter.addCategory(Intent.CATEGORY_HOME);
                filter.addCategory(Intent.CATEGORY_DEFAULT);
                final int N = list.size();
                Log.d("MyTag", "N:::::hyhyhyhy:::: = " + N);
                ComponentName[] set = new ComponentName[N];
                int bestMatch = 0;
                for (int i = 0; i < N; i++) {
                    ResolveInfo r = list.get(i);
                    set[i] = new ComponentName(r.activityInfo.packageName,
                            r.activityInfo.name);
                    Log.d("MyTag",
                            "r.activityInfo.packageName:::::hyhyhyhy:::: = "
                                    + r.activityInfo.packageName);
                    Log.d("MyTag", "r.activityInfo.name:::::hyhyhyhy:::: = "
                            + r.activityInfo.name);
                    if (r.match > bestMatch)
                        bestMatch = r.match;
                }
                // 设置默认launcher
                ComponentName launcher = new ComponentName(packageName,
                        className);
                try {
                    pm.addPreferredActivity(filter, bestMatch, set, launcher,
                            UserHandle.getCallingUserId());
                } catch (RemoteException e) {
                    throw new RuntimeException("Package manager has died", e);
                }
            }
        }
    }

需要 android:sharedUserId="android.uid.system"和系统签名

 <uses-permission android:name="android.permission.SET_PREFERRED_APPLICATIONS" />

编译时出错误，把android源码下的系统jar包导入即可