Android 设置默认Launcher

当系统中有多个Launcher桌面时，可通过以下方式设定默认的Launcher：

方法一：

偷懒的话，将不想要的Launcher，如Launcher3的AndroidManifest.xml文件中的HOME属性去掉，只保留自己想要的Launcher即可，前提是我们有其他Launcher的源码。弊端是去掉Home属性后再也无法进入。

方法二：

1.编辑：
frameworks/base/services/java/com/android/server/pm/PackageManagerService.java
文件中的
public void systemReady() {}函数，在最后添加以下代码段：

// TChip ZJ Add Below for Default Launcher
        if (isFirstBoot()) {
            // 修改为需要设置的 package name
            String examplePackageName = "com.tchip.carlauncher";

            // 修改为需要设置的 launcher activity name
            String exampleActivityName = "com.tchip.carlauncher.ui.activity.MainActivity";
            Intent intent = new Intent(Intent.ACTION_MAIN);
            intent.addCategory(Intent.CATEGORY_HOME);
            final int callingUserId = UserHandle.getCallingUserId();
            List resolveInfoList = queryIntentActivities(intent,
                    null, PackageManager.GET_META_DATA, callingUserId);
            if (resolveInfoList != null) {
                int size = resolveInfoList.size();
                for (int j = 0; j < size;) {
                    final ResolveInfo r = resolveInfoList.get(j);
                    if (!r.activityInfo.packageName.equals(examplePackageName)) {
                        resolveInfoList.remove(j);
                        size -= 1;
                    } else {
                        j++;
                    }
                }
                ComponentName[] set = new ComponentName[size];
                ComponentName defaultLauncher = new ComponentName(
                        examplePackageName, exampleActivityName);
                int defaultMatch = 0;
                for (int i = 0; i < size; i++) {
                    final ResolveInfo resolveInfo = resolveInfoList.get(i);
                    set[i] = new ComponentName(
                            resolveInfo.activityInfo.packageName,
                            resolveInfo.activityInfo.name);
                    if (defaultLauncher.getClassName().equals(
                            resolveInfo.activityInfo.name)) {
                        defaultMatch = resolveInfo.match;
                    }
                }
                IntentFilter filter = new IntentFilter();
                filter.addAction(Intent.ACTION_MAIN);
                filter.addCategory(Intent.CATEGORY_HOME);
                filter.addCategory(Intent.CATEGORY_DEFAULT);
                addPreferredActivity2(filter, defaultMatch, set,
                        defaultLauncher);
            }
        }
        // TChip ZJ Add Above for Default Launcher

2.添加以下函数：

/**
     * TChip ZJ Add for Default Launcher
     */
    public void addPreferredActivity2(IntentFilter filter, int match,
            ComponentName[] set, ComponentName activity) {
        Log.d("debug_default", "addPreferredActivity2 is called.");
        // writer
        synchronized (mPackages) {
            Slog.i(TAG, "Adding preferred activity " + activity + ":");
            filter.dump(new LogPrinter(Log.INFO, TAG), " ");
            mSettings.editPreferredActivitiesLPw(0).addFilter(
                    new PreferredActivity(filter, match, set, activity, true));
            scheduleWriteSettingsLocked();
        }
    }

3.修改PackageManagerService.java的函数findPreferredActivity：
（1）对removeMatches进行条件判断，在launcher时不remove：

if (!(intent.getAction() != null
                            && intent.getAction().equals(intent.ACTION_MAIN)
                            && intent.getCategories() != null && intent.getCategories()
                            .contains(intent.CATEGORY_HOME))) {

                        Slog.d(TAG, "launcher");
} else {
                        if (removeMatches) {
                            pir.removeFilter(pa);
                            if (DEBUG_PREFERRED) {
                                Slog.v(TAG, "Removing match " + pa.mPref.mComponent);
                            }
                            break;
                        }
}

（2）

    if (always && !pa.mPref.sameSet(query, priority)) {
            Slog.i(TAG, "Result set changed, dropping preferred activity for "
                    + intent + " type " + resolvedType);
            if (DEBUG_PREFERRED) {
                Slog.v(TAG, "Removing preferred activity since set changed "
                        + pa.mPref.mComponent);
            }
            pir.removeFilter(pa);
            // Re-add the filter as a "last chosen" entry (!always)
            PreferredActivity lastChosen = new PreferredActivity(pa,
                    pa.mPref.mMatch, null, pa.mPref.mComponent, false);
            pir.addFilter(lastChosen);
            mSettings.writePackageRestrictionsLPr(userId);
            return null;
        }

上面这段修改为下面的内容：

if (always && !pa.mPref.sameSet(query, priority)) {
            if (!(intent.getAction() != null
                    && intent.getAction().equals(intent.ACTION_MAIN)
                    && intent.getCategories() != null && intent.getCategories()
                    .contains(intent.CATEGORY_HOME))) { // MTK ADD
                Slog.i(TAG,
                        "Result set changed, dropping preferred activity for "
                                + intent + " type " + resolvedType);
                if (DEBUG_PREFERRED) {
                    Slog.v(TAG,
                            "Removing preferred activity since set changed "
                                    + pa.mPref.mComponent);
                }
                pir.removeFilter(pa);
                // Re-add the filter as a "last chosen" entry (!always)
                PreferredActivity lastChosen = new PreferredActivity(pa,
                        pa.mPref.mMatch, null, pa.mPref.mComponent, false);
                pir.addFilter(lastChosen);
                mSettings.writePackageRestrictionsLPr(userId);
                return null;
            }
        }
        Slog.i(TAG,
                "Result set not change, not drop preferred activity for special intent: "
                        + intent);// MTK ADD
        // Yay! Either the set matched or we're looking for the last chosen