Settings里面切换不同Launcher的代码流程

1.Android\packages\modules\Permission\PermissionController中的DefaultAppActivity中接收，根据packagename进行追踪路径如下：
DefaultAppActivity.java 
--->HandheldDefaultAppFragment.java  
--->DefaultAppChildFragment.java:setDefaultApp()
--->ManageRoleHolderStateLiveData.java
--->RoleService.java addRoleHolderAsUser()
--->RoleControllerServiceImpl.java:onAddRoleHolder()
--->RoleManager.java:addRoleHolderFromController()
--->RoleService.java:addRoleHolderFromController()
--->RoleUserState.java:addRoleHolder():readFile()
--->RolesPersistenceImpl.java:ROLES_FILE_NAME = "roles.xml"

位于Android\packages\modules\Permission\PermissionController\res\xml\roles.xml
可以通过修改roles.xml，来修改默认应用，但是我需要的是动态的修改：


2.vendor/mediatek/proprietary/packages/apps/PermissionController/src/com/android/permissioncontroller/role/ui/ManageRoleHolderStateLiveData.java

通过setRoleHolderAsUser函数实现，传入roleName和packageName，最终调用
android.app.role.RoleManager->addRoleHolderAsUser(...);

public void setRoleHolderAsUser(@NonNull String roleName, @NonNull String packageName,
            boolean add, int flags, @NonNull UserHandle user, @NonNull Context context) {
        if (getValue() != STATE_IDLE) {
            Log.e(LOG_TAG, "Already (tried) managing role holders, requested role: " + roleName
                    + ", requested package: " + packageName);
            return;
        }
        if (DEBUG) {
            Log.i(LOG_TAG, (add ? "Adding" : "Removing") + " package as role holder, role: "
                    + roleName + ", package: " + packageName);
        }
        mLastPackageName = packageName;
        mLastAdd = add;
        mLastFlags = flags;
        mLastUser = user;
        setValue(STATE_WORKING);

        RoleManager roleManager = context.getSystemService(RoleManager.class);
        Executor executor = context.getMainExecutor();
        Consumer<Boolean> callback = successful -> {
            if (successful) {
                if (DEBUG) {
                    Log.i(LOG_TAG, "Package " + (add ? "added" : "removed")
                            + " as role holder, role: " + roleName + ", package: " + packageName);
                }
                setValue(STATE_SUCCESS);
            } else {
                if (DEBUG) {
                    Log.i(LOG_TAG, "Failed to " + (add ? "add" : "remove")
                            + " package as role holder, role: " + roleName + ", package: "
                            + packageName);
                }
                setValue(STATE_FAILURE);
            }
        };
        if (add) {
            roleManager.addRoleHolderAsUser(roleName, packageName, flags, user, executor, callback);
        } else {
            roleManager.removeRoleHolderAsUser(roleName, packageName, flags, user, executor,
                    callback);
        }
    }

各默认应用对应的 roleName 如下:
电话
role: android.app.role.DIALER, package: com.android.dialer
短信
role: android.app.role.SMS, package: com.android.mms
主屏幕
role: android.app.role.HOME, package: com.android.launcher3
浏览器
role: android.app.role.BROWSER, package: com.android.browser

可以通过RoleManager->addRoleHolderAsUser(...),在某个服务中重写默认的app包名！


// 默认浏览器
./frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java

import android.app.role.RoleManager;
import android.os.UserHandle;
import android.os.Process;
import java.util.concurrent.Executor;
import java.util.function.Consumer;

public void setDefaultBrowser(Context context, String packageName) {
    String roleName = "android.app.role.BROWSER";
    boolean add = true;
    int flags = 0;
    UserHandle user = Process.myUserHandle();
    Log.d("TAG", "role: "+ roleName + ", package: " + packageName);
    RoleManager roleManager = context.getSystemService(RoleManager.class);
    Executor executor = context.getMainExecutor();
    Consumer<Boolean> callback = successful -> {
        if (successful) {
            Log.d("TAG", "Success , role: " + roleName + ", package: " + packageName);
        } else {
            Log.d("TAG", "Failed , role: " + roleName + ", package: "+ packageName);
        }
    };
    roleManager.addRoleHolderAsUser(roleName, packageName, flags, user, executor, callback);
}

@Override
public void systemReady() {
	...
	synchronized (mLock) {
            mSystemReady = true;
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    updateSettings();
                }
            });
            // If this happens, for whatever reason, systemReady came later than systemBooted.
            // And keyguard should be already bound from systemBooted
            if (mSystemBooted) {
                mKeyguardDelegate.onBootCompleted();
            }
        }
        mAutofillManagerInternal = LocalServices.getService(AutofillManagerInternal.class);
	setDefaultBrowser(mContext, "com.xx");//add
	...
}

2.系统给与的pm命令，选中setHomeActivity
frameworks/base/services/core/java/com/android/server/pm/PackageManagerShellCommand.java

PS C:\Users\Aaaa>  adb shell -x
rk3566_r:/ $ pm set-home-activity com.xxx.mylauncher
Success


import android.app.role.IRoleManager;
import android.app.role.RoleManager;
import android.os.ServiceManager;
import java.util.concurrent.CompletableFuture;
import android.os.RemoteCallback;
import android.content.Context;

...

        String default_home_package = SystemProperties.get("persist.sys.xxxxx", null);
        final CompletableFuture<Boolean> future = new CompletableFuture<>();
        final RemoteCallback callback = new RemoteCallback(res -> future.complete(res != null));
        try {
            IRoleManager roleManager = android.app.role.IRoleManager.Stub.asInterface(
                    ServiceManager.getServiceOrThrow(Context.ROLE_SERVICE));
            roleManager.addRoleHolderAsUser(RoleManager.ROLE_HOME, default_home_package,
                    0, 0, callback);
            boolean success = future.get();
            if (success) {
                android.util.Log.v("tww", "DefaultActivity success");
            } else {
                android.util.Log.v("tww", "DefaultActivity Error: Failed to set default home.");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
...