// in onCreate method
String appName = "Gmail";
String packageName = "com.google.android.gm";
openApp(context, appName, packageName);

public static void openApp(Context context, String appName, String packageName) {
    if (isAppInstalled(context, packageName))
        if (isAppEnabled(context, packageName))
            context.startActivity(context.getPackageManager().getLaunchIntentForPackage(packageName));
        else Toast.makeText(context, appName + " app is not enabled.", Toast.LENGTH_SHORT).show();
    else Toast.makeText(context, appName + " app is not installed.", Toast.LENGTH_SHORT).show();
}

private static boolean isAppInstalled(Context context, String packageName) {
    PackageManager pm = context.getPackageManager();
    try {
        pm.getPackageInfo(packageName, PackageManager.GET_ACTIVITIES);
        return true;
    } catch (PackageManager.NameNotFoundException ignored) {
    }
    return false;
}

private static boolean isAppEnabled(Context context, String packageName) {
    boolean appStatus = false;
    try {
        ApplicationInfo ai = context.getPackageManager().getApplicationInfo(packageName, 0);
        if (ai != null) {
            appStatus = ai.enabled;
        }
    } catch (PackageManager.NameNotFoundException e) {
        e.printStackTrace();
    }
    return appStatus;
}

下面是我的例子，如果有人觉得有用，我就从我的应用程序中启动条形码/QR码扫描仪

Intent intent = new Intent("com.google.zxing.client.android.SCAN");
intent.setPackage("com.google.zxing.client.android");

try 
{
    startActivityForResult(intent, SCAN_REQUEST_CODE);
} 
catch (ActivityNotFoundException e) 
{
    //implement prompt dialog asking user to download the package
    AlertDialog.Builder downloadDialog = new AlertDialog.Builder(this);
    downloadDialog.setTitle(stringTitle);
    downloadDialog.setMessage(stringMessage);
    downloadDialog.setPositiveButton("yes",
            new DialogInterface.OnClickListener() 
            {
                public void onClick(DialogInterface dialogInterface, int i) 
                {
                    Uri uri = Uri.parse("market://search?q=pname:com.google.zxing.client.android");
                    Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                    try
                    {
                        myActivity.this.startActivity(intent);
                    }
                    catch (ActivityNotFoundException e)
                    {
                        Dialogs.this.showAlert("ERROR", "Google Play Market not found!");
                    }
                }
            });
    downloadDialog.setNegativeButton("no",
            new DialogInterface.OnClickListener() 
            {
                public void onClick(DialogInterface dialog, int i) 
                {
                    dialog.dismiss();
                }
            });
    downloadDialog.show();
}

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)
}

如果你知道数据和安装的包的反应，你只需在启动之前将这些信息添加到你的intent实例中。

如果你可以访问其他应用程序的AndroidManifest，你可以在那里看到所有需要的信息。

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

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);
    }
}