通过Launcher启动应用的过程分析_launcherappsservice

通过Launcher启动应用的过程分析

通过Lanucher启动 应用时会调用Lanucher的onClick方法。

     Lanucher.java
    /**
     * Launches the intent referred by the clicked shortcut.
     *
     * @param v The view representing the clicked shortcut.
     */
    public void onClick(View v) {
        // Make sure that rogue clicks don't get through while allapps is launching, or after the
        // view has detached (it's possible for this to happen if the view is removed mid touch).
        if (v.getWindowToken() == null) {
            return;
        }
 
        if (!mWorkspace.isFinishedSwitchingState()) {
            return;
        }
 
        Object tag = v.getTag();
        /*
          ShortcutInfo是Lanucher界面上的应用图标，封装了应用的信息吧
        */
        if (tag instanceof ShortcutInfo) {
            // Open shortcut
            final Intent intent = ((ShortcutInfo) tag).intent;
         /*
           构造了数组保存要点击的应用图标在界面的位置
          */
            int[] pos = new int[2];
            v.getLocationOnScreen(pos);
            intent.setSourceBounds(new Rect(pos[0], pos[1],
                    pos[0] + v.getWidth(), pos[1] + v.getHeight()));
           /*
             这一步开始去启动Activity，什么时候能返回呢，应该是调用传递给了系统服务后就可以了
            */
            boolean success = startActivitySafely(v, intent, tag);
 
            if (success && v instanceof BubbleTextView) {
                mWaitingForResume = (BubbleTextView) v;
                mWaitingForResume.setStayPressed(true);
            }
        } else if (tag instanceof FolderInfo) {
            if (v instanceof FolderIcon) {
                FolderIcon fi = (FolderIcon) v;
                handleFolderClick(fi);
            }
        } else if (v == mAllAppsButton) {
            if (isAllAppsVisible()) {
                showWorkspace(true);
            } else {
                onClickAllAppsButton(v);
            }
        }
    }

 Lanucher.java
 
 boolean startActivitySafely(View v, Intent intent, Object tag) {
        boolean success = false;
        try {
            success = startActivity(v, intent, tag);
        } catch (ActivityNotFoundException e) {
            Toast.makeText(this, R.string.activity_not_found, Toast.LENGTH_SHORT).show();
            Log.e(TAG, "Unable to launch. tag=" + tag + " intent=" + intent, e);
        }
        return success;
    }
 
 
boolean startActivity(View v, Intent intent, Object tag) {
        //设置FLAG的目的是保证每次都在新的Task中启动应用，每一个应用都有自己的task
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 
        try {
            // Only launch using the new animation if the shortcut has not opted out (this is a
            // private contract between launcher and may be ignored in the future).
            boolean useLaunchAnimation = (v != null) &&
                    !intent.hasExtra(INTENT_EXTRA_IGNORE_LAUNCH_ANIMATION);
            UserHandle user = (UserHandle) intent.getParcelableExtra(ApplicationInfo.EXTRA_PROFILE);
            /*
             该类用于检索当前用户可以启动的所有的Activity的列表以及用户可见的相关的配置文件，Lanucher主要使用该 类，可以通过配置文件查询所有的APP的信息，PackageManager不会为其他的配置文件发送广播，所以如果你想要监听这这些应用包的变化，可以注册监听此PackagerManager的广播Intent.ACTION_MANAGED_PROFILE_ADDED and Intent.ACTION_MANAGED_PROFILE_REMOVED.
            */
 
            LauncherApps launcherApps = (LauncherApps)
                    this.getSystemService(Context.LAUNCHER_APPS_SERVICE);
            if (useLaunchAnimation) {
                //Activity过度动画相关
                ActivityOptions opts = ActivityOptions.makeScaleUpAnimation(v, 0, 0,
                        v.getMeasuredWidth(), v.getMeasuredHeight());
                if (user == null || user.equals(android.os.Process.myUserHandle())) {
                    // Could be launching some bookkeeping activity
                    startActivity(intent, opts.toBundle());
                } else {
                    launcherApps.startMainActivity(intent.getComponent(), user,
                            intent.getSourceBounds(),
                            opts.toBundle());
                }
            } else {
                //不需要启动动画，下面的判断应该是判断是新启动的应用还是已经有的应用
                if (user == null || user.equals(android.os.Process.myUserHandle())) {
                    //Lanucher继承自Activity所以调用到父类Activity中
                    startActivity(intent);
                } else {
                    launcherApps.startMainActivity(intent.getComponent(), user,
                            intent.getSourceBounds(), null);
                }
            }
            return true;
        } catch (SecurityException e) {
            Toast.makeText(this, R.string.activity_not_found, Toast.LENGTH_SHORT).show();
            Log.e(TAG, "Launcher does not have the permission to launch " + intent +
                    ". Make sure to create a MAIN intent-filter for the corresponding activity " +
                    "or use the exported attribute for this activity. "
                    + "tag="+ tag + " intent=" + intent, e);
        }
        return false;
    }

startActivity会调用到Activity的如下代码

Activity.java
   @Override
    public void startActivity(Intent intent, @Nullable Bundle options) {
        //Bundle中保存了之前启动得Activity的信息，如果之前没有Activity则信息为空
        if (options != null) {
            startActivityForResult(intent, -1, options);
        } else {
            // Note we want to go through this call for compatibility with
            // applications that may have overridden the method.
            startActivityForResult(intent, -1);
        }
    }

launcherApps.startMainActivity,   mService是LanucherAppsService.java

LanucherApps.java
   /**
     * Starts a Main activity in the specified profile.
     *
     * @param component The ComponentName of the activity to launch
     * @param user The UserHandle of the profile
     * @param sourceBounds The Rect containing the source bounds of the clicked icon
     * @param opts Options to pass to startActivity
     */
    public void startMainActivity(ComponentName component, UserHandle user, Rect sourceBounds,
            Bundle opts) {
        logErrorForInvalidProfileAccess(user);
        if (DEBUG) {
            Log.i(TAG, "StartMainActivity " + component + " " + user.getIdentifier());
        }
        try {
            mService.startActivityAsUser(mContext.getPackageName(),
                    component, sourceBounds, opts, user);
        } catch (RemoteException re) {
            throw re.rethrowFromSystemServer();
        }
    }

LancherAppsService.java 
       @Override
        public void startActivityAsUser(String callingPackage,
                ComponentName component, Rect sourceBounds,
                Bundle opts, UserHandle user) throws RemoteException {
            if (!canAccessProfile(callingPackage, user, "Cannot start activity")) {
                return;
            }
            if (!isUserEnabled(user)) {
                throw new IllegalStateException("Cannot start activity for disabled profile "  + user);
            }
 
            Intent launchIntent = new Intent(Intent.ACTION_MAIN);
            launchIntent.addCategory(Intent.CATEGORY_LAUNCHER);
            launchIntent.setSourceBounds(sourceBounds);
            launchIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
                    | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
            launchIntent.setPackage(component.getPackageName());
 
            final int callingUid = injectBinderCallingUid();
            long ident = Binder.clearCallingIdentity();
            try {
                final PackageManagerInternal pmInt =
                        LocalServices.getService(PackageManagerInternal.class);
                ActivityInfo info = pmInt.getActivityInfo(component,
                        PackageManager.MATCH_DIRECT_BOOT_AWARE
                                | PackageManager.MATCH_DIRECT_BOOT_UNAWARE,
                        callingUid, user.getIdentifier());
                if (!info.exported) {
                    throw new SecurityException("Cannot launch non-exported components "
                            + component);
                }
 
                // Check that the component actually has Intent.CATEGORY_LAUCNCHER
                // as calling startActivityAsUser ignores the category and just
                // resolves based on the component if present.
                List<ResolveInfo> apps = pmInt.queryIntentActivities(launchIntent,
                        PackageManager.MATCH_DIRECT_BOOT_AWARE
                                | PackageManager.MATCH_DIRECT_BOOT_UNAWARE,
                        callingUid, user.getIdentifier());
                final int size = apps.size();
                /*
                   没搞清楚这个for循环在干嘛，for循环的意义在保证系统中存在相应的Activity信息？
                */
                for (int i = 0; i < size; ++i) {
                    ActivityInfo activityInfo = apps.get(i).activityInfo;
                    if (activityInfo.packageName.equals(component.getPackageName()) &&
                            activityInfo.name.equals(component.getClassName())) {
                        // Found an activity with category launcher that matches
                        // this component so ok to launch.
                        launchIntent.setComponent(component);
                        mContext.startActivityAsUser(launchIntent, opts, user);
                        return;
                    }
                }
                throw new SecurityException("Attempt to launch activity without "
                        + " category Intent.CATEGORY_LAUNCHER " + component);
            } finally {
                Binder.restoreCallingIdentity(ident);
            }
        }