启动新活动的步骤如下:

1.获取包的意图

2.如果意图为空重定向用户到播放商店

3.如果意图不为空，打开活动

public void launchNewActivity(Context context, String packageName) {
    Intent intent = null;
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.CUPCAKE) {
        intent = context.getPackageManager().getLaunchIntentForPackage(packageName);
    }
    if (intent == null) {
        try {
            intent = new Intent(Intent.ACTION_VIEW);
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            intent.setData(Uri.parse("market://details?id=" + packageName));
            context.startActivity(intent);
        } catch (android.content.ActivityNotFoundException anfe) {
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=" + packageName)));
        }
    } else {
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
    }
}

由于kotlin现在变得非常流行，我认为在kotlin中也提供一个简单的解决方案是合适的。

var launchIntent: Intent? = null
try {
    launchIntent = packageManager.getLaunchIntentForPackage("applicationId")
} catch (ignored: Exception) {
}
if (launchIntent == null) {
    startActivity(Intent(Intent.ACTION_VIEW).setData(Uri.parse("https://play.google.com/store/apps/details?id=" + "applicationId")))
} else {
    startActivity(launchIntent)
}

试试下面的代码:

Intent intent = new Intent(Intent.ACTION_MAIN);
intent.setComponent(new ComponentName("package_name", "Class_name"));
if (intent.resolveActivity(getPackageManager()) != null) 
{
   startActivity(intent);
}

可以使用Intent来启动应用程序的activity。setClassName根据文档。

一个例子:

val activityName = "com.google.android.apps.muzei.MuzeiActivity" // target activity name
val packageName = "net.nurik.roman.muzei" // target package's name
val intent = Intent().setClassName(packageName, activityName)
startActivity(intent)

要在当前应用程序之外打开它，在开始intent之前添加这个标志。

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)

这里有一个相关的答案

从API 30 (Android 11)开始，你可以通过launchIntentForPackage接收nullpointerexception

val launchIntent: Intent? = activity.packageManager.getLaunchIntentForPackage("com.google.android.gm")
startActivity(launchIntent) 

为了避免这种情况，您需要将所需的包添加到清单中

<queries>
    <package android:name="com.google.android.gm" />
</queries>

这里是文档 https://developer.android.com/training/package-visibility

而媒体文章 https://medium.com/androiddevelopers/package-visibility-in-android-11-cc857f221cd9

private fun openOtherApp() {
        val sendIntent = packageManager.getLaunchIntentForPackage("org.mab.dhyanaqrscanner")
        startActivity(sendIntent)
        finishAffinity()
    }