Android系统开发-选择并启动默认Launcher

如果在Android设备上又安装了一个Launcher应用，当我们返回主页的时候，Android就会弹出一个弹窗，要用户 选择要启动的Launcher应用，如下图所示：

这个是普通Android设备的正常流程，现在我们的需求是不再显示这个提示窗，在设置中增加一个选择默认启动Launcher的页面，默认选择Launcher3。

Settings

在设置中增加一个这样的页面，显示所有声明了"android.intent.category.HOME"的应用

 private fun getAllLauncherApps(): MutableList<AppInfo> {

        val list = ArrayList<AppInfo>()

        val launchIntent = Intent(Intent.ACTION_MAIN, null)

            .addCategory(Intent.CATEGORY_HOME)

        val intents = packageManager.queryIntentActivities(launchIntent, 0)


        //遍历

        for (ri in intents) {

            //得到包名

            val packageName = ri.activityInfo.applicationInfo.packageName

            if (packageName == "com.android.settings") { //不显示原生设置

                continue

            }

            //得到图标

            val icon = ri.loadIcon(packageManager)

            //得到应用名称

            val appName = ri.loadLabel(packageManager).toString()


            //封装应用信息对象

            val appInfo = AppInfo(icon, appName, packageName)

            //添加到list

            list.add(appInfo)

        }

        return list

    }

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使用PackageManager提供的queryIntentActivities方法就可以获取所有Launcher应用，原生设置中也有Activity声明了HOME属性，在这里就把它屏蔽掉。

默认选择Launcher3应用为默认启动

private val DEFAULT_LAUNCHER = "my_default_launcher"

defaultLauncher = Settings.Global.getString(contentResolver, DEFAULT_LAUNCHER)

if (defaultLauncher.isNullOrEmpty()) {

    defaultLauncher = "com.android.launcher3"

    Settings.Global.putString(contentResolver, DEFAULT_LAUNCHER, defaultLauncher)

}

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当选择另一个应用，就把选择应用的包名设置到 Settings.Global中。

这样应用选择页面完成，也设置了一个全局的参数提供给系统。

启动

最开始提到了Launcher选择弹窗，我们就考虑在这里做点事，把弹窗的逻辑给跳过，就可以实现默认启动。

弹窗源码位于frameworks/base/core/java/com/android/internal/app/ResolverActivity.java

在这里就不具体分析源码了，就看关键部分

public boolean configureContentView(List<Intent> payloadIntents, Intent[] initialIntents,

            List<ResolveInfo> rList, boolean alwaysUseOption) {

        // The last argument of createAdapter is whether to do special handling

        // of the last used choice to highlight it in the list.  We need to always

        // turn this off when running under voice interaction, since it results in

        // a more complicated UI that the current voice interaction flow is not able

        // to handle.

        mAdapter = createAdapter(this, payloadIntents, initialIntents, rList,

                mLaunchedFromUid, alwaysUseOption && !isVoiceInteraction());


        final int layoutId;

        if (mAdapter.hasFilteredItem()) {

            layoutId = R.layout.resolver_list_with_default;

            alwaysUseOption = false;

        } else {

            layoutId = getLayoutResource();

        }

        mAlwaysUseOption = alwaysUseOption;


        int count = mAdapter.getUnfilteredCount();

        if (count == 1 && mAdapter.getOtherProfile() == null) {

            // Only one target, so we're a candidate to auto-launch!

            final TargetInfo target = mAdapter.targetInfoForPosition(0, false);

            if (shouldAutoLaunchSingleChoice(target)) {

                safelyStartActivity(target);

                mPackageMonitor.unregister();

                mRegistered = false;

                finish();

                return true;

            }

        }

        if (count > 0) {

            // add by liuwei,if set my_default_launcher,start default

            String defaultlauncher = Settings.Global.getString(this.getContentResolver(), "my_default_launcher");


            final TargetInfo defaultTarget = mAdapter.targetInfoForDefault(defaultlauncher);

            if(defaultTarget != null){

                safelyStartActivity(defaultTarget);

                mPackageMonitor.unregister();

                mRegistered = false;

                finish();

                return true;

            }

            //end

            setContentView(layoutId);

            mAdapterView = (AbsListView) findViewById(R.id.resolver_list);

            onPrepareAdapterView(mAdapterView, mAdapter, alwaysUseOption);

        } else {

            setContentView(R.layout.resolver_list);


            final TextView empty = (TextView) findViewById(R.id.empty);

            empty.setVisibility(View.VISIBLE);


            mAdapterView = (AbsListView) findViewById(R.id.resolver_list);

            mAdapterView.setVisibility(View.GONE);

        }

        return false;

    }

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在configureContentView中判断launcher应用个数，如果为1，则直接启动，finish当前页面。下面判断count>0，我们就在这里面增加自己的逻辑，获取配置的Settings.Global参数，再去Adapter中判断是否有应用包名和参数匹配，如果有就safelyStartActivity()，关闭弹窗。如果没有匹配包名，就走正常流程，弹窗提示用户。

mAdapter.targetInfoForDefault函数是在 public class ResolveListAdapter extends BaseAdapter中增加函数

 public TargetInfo targetInfoForDefault(String myDefault){

            if(myDefault == null){

                return null;

            }


            TargetInfo info = null;

            for(int i=0;i<mDisplayList.size();i++){

                String disPackageName = mDisplayList.get(i).getResolveInfo().activityInfo.applicationInfo.packageName;

                if(myDefault.equals(disPackageName) ){

                    info = mDisplayList.get(i);

                    break;

                }

            }

            return info;

        }


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OK，功能实现完成，自测也没有问题。