首先需要知道包名，参考实现如下

import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import java.util.List;

    private String getLaunchActivityForPackage(String packageName){
        PackageManager pm = getPackageManager();
        Intent intentToResolve = new Intent(Intent.ACTION_MAIN);
        intentToResolve.addCategory(Intent.CATEGORY_INFO);
        intentToResolve.setPackage(packageName);
        List<ResolveInfo> ris = pm.queryIntentActivities(intentToResolve, 0);
        // Otherwise, try to find a main launcher activity.
        if (ris == null || ris.size() <= 0) {
            // reuse the intent instance
            intentToResolve.removeCategory(Intent.CATEGORY_INFO);
            intentToResolve.addCategory(Intent.CATEGORY_LAUNCHER);
            intentToResolve.setPackage(packageName);
            ris = pm.queryIntentActivities(intentToResolve, 0);
        }
        if (ris == null || ris.size() <= 0) {
            return null;
        }
        return ris.get(0).activityInfo.name;
    }

这个实现实际上是 ApplicationPackageManager 的 getLaunchIntentForPackage 的实现，稍微改一下就可以实现我们的需要了。原实现如下

    @Override
    public Intent getLaunchIntentForPackage(String packageName) {
        // First see if the package has an INFO activity; the existence of
        // such an activity is implied to be the desired front-door for the
        // overall package (such as if it has multiple launcher entries).
        Intent intentToResolve = new Intent(Intent.ACTION_MAIN);
        intentToResolve.addCategory(Intent.CATEGORY_INFO);
        intentToResolve.setPackage(packageName);
        List<ResolveInfo> ris = queryIntentActivities(intentToResolve, 0);

        // Otherwise, try to find a main launcher activity.
        if (ris == null || ris.size() <= 0) {
            // reuse the intent instance
            intentToResolve.removeCategory(Intent.CATEGORY_INFO);
            intentToResolve.addCategory(Intent.CATEGORY_LAUNCHER);
            intentToResolve.setPackage(packageName);
            ris = queryIntentActivities(intentToResolve, 0);
        }
        if (ris == null || ris.size() <= 0) {
            return null;
        }
        Intent intent = new Intent(intentToResolve);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setClassName(ris.get(0).activityInfo.packageName,
                ris.get(0).activityInfo.name);
        return intent;
    }

因为这个函数的实现默认给 intent 加了 Intent.FLAG_ACTIVITY_NEW_TASK ，某些时候不一定需要。

Android 获取某个应用的 Launch Activity