Android源码分析之设置默认启动的Launcher

//Android6.0
    boolean startHomeActivityLocked(int userId, String reason) {
        //工厂测试模式
        if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
                && mTopAction == null) {
            // We are running in factory test mode, but unable to find
            // the factory test app, so just sit around displaying the
            // error message and don't try to start anything.
            return false;
        }
        //获取Home Intent
        Intent intent = getHomeIntent();
        //获取Activity信息
        ActivityInfo aInfo =
            resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
        if (aInfo != null) {
            intent.setComponent(new ComponentName(
                    aInfo.applicationInfo.packageName, aInfo.name));
            // Don't do this if the home app is currently being
            // instrumented.
            aInfo = new ActivityInfo(aInfo);
            //根据userId获取应用信息
            aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
            //获取应用进程，每个android进程，在AMS中对应有一个ProcessRecord
            ProcessRecord app = getProcessRecordLocked(aInfo.processName,
                    aInfo.applicationInfo.uid, true);
            if (app == null || app.instrumentationClass == null) {
                //如果进程不存在，就要在启动时为该应用新建一个堆栈(FLAG_ACTIVITY_NEW_TASK)
                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
                //启动Home Activity(Launcher)
                mStackSupervisor.startHomeActivity(intent, aInfo, reason);
            }
        }

        return true;
    }

//Android6.0
    void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason) {
        //将Home Activity移动到栈顶
        moveHomeStackTaskToTop(HOME_ACTIVITY_TYPE, reason);
        //启动Home Activity
        startActivityLocked(null /* caller */, intent, null /* resolvedType */, aInfo,
                null /* voiceSession */, null /* voiceInteractor */, null /* resultTo */,
                null /* resultWho */, 0 /* requestCode */, 0 /* callingPid */, 0 /* callingUid */,
                null /* callingPackage */, 0 /* realCallingPid */, 0 /* realCallingUid */,
                0 /* startFlags */, null /* options */, false /* ignoreTargetSecurity */,
                false /* componentSpecified */,
                null /* outActivity */, null /* container */,  null /* inTask */);
        if (inResumeTopActivity) {
            // If we are in resume section already, home activity will be initialized, but not
            // resumed (to avoid recursive resume) and will stay that way until something pokes it
            // again. We need to schedule another resume.
            scheduleResumeTopActivities();
        }
    }

/**
 * This activity is displayed when the system attempts to start an Intent for
 * which there is more than one matching activity, allowing the user to decide
 * which to go to.  It is not normally used directly by application developers.
 */

@Override
    protected void onCreate(Bundle savedInstanceState) {
        // Use a specialized prompt when we're handling the 'Home' app startActivity()
        //当启动的是Launcher时会弹出一个专门的提示
        final Intent intent = makeMyIntent();
        final Set<String> categories = intent.getCategories();
        if (Intent.ACTION_MAIN.equals(intent.getAction())
                && categories != null
                && categories.size() == 1
                && categories.contains(Intent.CATEGORY_HOME)) {
            // Note: this field is not set to true in the compatibility version.
            mResolvingHome = true;
        }

        setSafeForwardingMode(true);

        onCreate(savedInstanceState, intent, null, 0, null, null, true);
    }

protected void onCreate(Bundle savedInstanceState, Intent intent,
            CharSequence title, int defaultTitleRes, Intent[] initialIntents,
            List<ResolveInfo> rList, boolean alwaysUseOption) {
        setTheme(R.style.Theme_DeviceDefault_Resolver);
        super.onCreate(savedInstanceState);

        // Determine whether we should show that intent is forwarded
        // from managed profile to owner or other way around.
        setProfileSwitchMessageId(intent.getContentUserHint());

        try {
            //获取UID，Android支持多用户，不同用户可能Launcher不同
            mLaunchedFromUid = ActivityManagerNative.getDefault().getLaunchedFromUid(
                    getActivityToken());
        } catch (RemoteException e) {
            mLaunchedFromUid = -1;
        }

        if (mLaunchedFromUid < 0 || UserHandle.isIsolated(mLaunchedFromUid)) {
            // Gulp!
            finish();
            return;
        }
        //获取PackageManager
        mPm = getPackageManager();

        mPackageMonitor.register(this, getMainLooper(), false);
        mRegistered = true;
        //获取ActivityManager
        final ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        //获取Launcher Icon的大小
        mIconDpi = am.getLauncherLargeIconDensity();

        // Add our initial intent as the first item, regardless of what else has already been added.
        mIntents.add(0, new Intent(intent));
        //获取推荐的包名
        final String referrerPackage = getReferrerPackageName();

        mResolverComparator = new ResolverComparator(this, getTargetIntent(), referrerPackage);
        //设置布局，类似于setContentView
        if (configureContentView(mIntents, initialIntents, rList, alwaysUseOption)) {
            return;
        }

        // Prevent the Resolver window from becoming the top fullscreen window and thus from taking
        // control of the system bars.
        //防止选择窗口变成全屏
        getWindow().clearFlags(FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR);
        //接下来就是初始化界面，设置监听器
        final ResolverDrawerLayout rdl = (ResolverDrawerLayout) findViewById(R.id.contentPanel);
        if (rdl != null) {
            rdl.setOnDismissedListener(new ResolverDrawerLayout.OnDismissedListener() {
                @Override
                public void onDismissed() {
                    finish();
                }
            });
            if (isVoiceInteraction()) {
                rdl.setCollapsed(false);
            }
            mResolverDrawerLayout = rdl;
        }

        if (title == null) {
            title = getTitleForAction(intent.getAction(), defaultTitleRes);
        }
        if (!TextUtils.isEmpty(title)) {
            final TextView titleView = (TextView) findViewById(R.id.title);
            if (titleView != null) {
                titleView.setText(title);
            }
            setTitle(title);

            // Try to initialize the title icon if we have a view for it and a title to match
            final ImageView titleIcon = (ImageView) findViewById(R.id.title_icon);
            if (titleIcon != null) {
                ApplicationInfo ai = null;
                try {
                    if (!TextUtils.isEmpty(referrerPackage)) {
                        ai = mPm.getApplicationInfo(referrerPackage, 0);
                    }
                } catch (NameNotFoundException e) {
                    Log.e(TAG, "Could not find referrer package " + referrerPackage);
                }

                if (ai != null) {
                    titleIcon.setImageDrawable(ai.loadIcon(mPm));
                }
            }
        }

        final ImageView iconView = (ImageView) findViewById(R.id.icon);
        final DisplayResolveInfo iconInfo = mAdapter.getFilteredItem();
        if (iconView != null && iconInfo != null) {
            new LoadIconIntoViewTask(iconInfo, iconView).execute();
        }

        if (alwaysUseOption || mAdapter.hasFilteredItem()) {
            final ViewGroup buttonLayout = (ViewGroup) findViewById(R.id.button_bar);
            if (buttonLayout != null) {
                buttonLayout.setVisibility(View.VISIBLE);
                //Always按钮
                mAlwaysButton = (Button) buttonLayout.findViewById(R.id.button_always);
                //Once按钮
                mOnceButton = (Button) buttonLayout.findViewById(R.id.button_once);
            } else {
                mAlwaysUseOption = false;
            }
        }

        if (mAdapter.hasFilteredItem()) {
            setAlwaysButtonEnabled(true, mAdapter.getFilteredPosition(), false);
            mOnceButton.setEnabled(true);
        }

        mProfileView = findViewById(R.id.profile_button);
        if (mProfileView != null) {
            mProfileView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    final DisplayResolveInfo dri = mAdapter.getOtherProfile();
                    if (dri == null) {
                        return;
                    }

                    // Do not show the profile switch message anymore.
                    mProfileSwitchMessageId = -1;

                    onTargetSelected(dri, false);
                    finish();
                }
            });
            bindProfileView();
        }

        if (isVoiceInteraction()) {
            onSetupVoiceInteraction();
        }

        getWindow().getDecorView().addOnAttachStateChangeListener(
                new OnAttachStateChangeListener() {
            @Override
            public void onViewAttachedToWindow(View v) {
                v.getViewRootImpl().setDrawDuringWindowsAnimating(true);
            }

            @Override
            public void onViewDetachedFromWindow(View v) {
            }
        });
    }

public void onButtonClick(View v) {
        //获取Button id
        final int id = v.getId();
        startSelected(mAlwaysUseOption ?
                        mAdapterView.getCheckedItemPosition() : mAdapter.getFilteredPosition(),
                id == R.id.button_always,
                mAlwaysUseOption);
    }

void startSelected(int which, boolean always, boolean filtered) {
        if (isFinishing()) {
            return;
        }
        //ResolveInfo是Activity信息的集合
        ResolveInfo ri = mAdapter.resolveInfoForPosition(which, filtered);
        if (mResolvingHome && hasManagedProfile() && !supportsManagedProfiles(ri)) {
            Toast.makeText(this, String.format(getResources().getString(
                    com.android.internal.R.string.activity_resolver_work_profiles_support),
                    ri.activityInfo.loadLabel(getPackageManager()).toString()),
                    Toast.LENGTH_LONG).show();
            return;
        }
        //获取要启动的Activity(Launcher)
        //TargetInfo包含了Activity的信息
        TargetInfo target = mAdapter.targetInfoForPosition(which, filtered);
        if (onTargetSelected(target, always)) {
            finish();
        }
    }

protected boolean onTargetSelected(TargetInfo target, boolean alwaysCheck) {
        //获取Activity信息
        final ResolveInfo ri = target.getResolveInfo();
        final Intent intent = target != null ? target.getResolvedIntent() : null;
            ........

            if (filter != null) {
                final int N = mAdapter.mOrigResolveList.size();
                ComponentName[] set = new ComponentName[N];
                int bestMatch = 0;
                for (int i=0; i<N; i++) {
                    ResolveInfo r = mAdapter.mOrigResolveList.get(i).getResolveInfoAt(0);
                    set[i] = new ComponentName(r.activityInfo.packageName,
                            r.activityInfo.name);
                    if (r.match > bestMatch) bestMatch = r.match;
                }
                //always被选中
                if (alwaysCheck) {
                    final int userId = getUserId();
                    final PackageManager pm = getPackageManager();

                    // Set the preferred Activity
                    //设置首选的Activity
                    pm.addPreferredActivity(filter, bestMatch, set, intent.getComponent());
                    //省略
                    ........
                } else {
                    //省略
                  ........
                }
            }
        }

        if (target != null) {
            safelyStartActivity(target);
        }
        return true;
    }