Intent shareIntent = new Intent(android.content.Intent.ACTION_SEND);
        shareIntent.setType("text/plain");
        shareIntent.putExtra(android.content.Intent.EXTRA_TEXT, "Content to share");
        PackageManager pm = contexto.getPackageManager();
        List<ResolveInfo> activityList = pm.queryIntentActivities(shareIntent, 0);
        for (final ResolveInfo app : activityList) {
            if ("com.twitter.android.PostActivity".equals(app.activityInfo.name)) {
                final ActivityInfo activity = app.activityInfo;
                final ComponentName name = new ComponentName(activity.applicationInfo.packageName, activity.name);
                shareIntent.addCategory(Intent.CATEGORY_LAUNCHER);
                shareIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
                shareIntent.setComponent(name);
                contexto.startActivity(shareIntent);
                break;
            }
        }

android.content.ActivityNotFoundException: Unable to find explicit activity class {com.twitter.android/com.twitter.android.PostActivity}; have you declared this activity in your AndroidManifest.xml?

Intent intent = null;
try {
    // get the Twitter app if possible
    this.getPackageManager().getPackageInfo("com.twitter.android", 0);
    intent = new Intent(Intent.ACTION_VIEW, Uri.parse("twitter://user?user_id=USERID"));
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
} catch (Exception e) {
    // no Twitter app, revert to browser
    intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://twitter.com/USERID_OR_PROFILENAME"));
}
this.startActivity(intent);

Intent tweetIntent = new Intent(Intent.ACTION_SEND);
tweetIntent.putExtra(Intent.EXTRA_TEXT, "This is a Test.");
tweetIntent.setType("text/plain");

PackageManager packManager = getPackageManager();
List<ResolveInfo> resolvedInfoList = packManager.queryIntentActivities(tweetIntent,  PackageManager.MATCH_DEFAULT_ONLY);

boolean resolved = false;
for(ResolveInfo resolveInfo: resolvedInfoList){
    if(resolveInfo.activityInfo.packageName.startsWith("com.twitter.android")){
        tweetIntent.setClassName(
            resolveInfo.activityInfo.packageName,
            resolveInfo.activityInfo.name );
        resolved = true;
        break;
    }
}
if(resolved){
    startActivity(tweetIntent);
}else{
    Toast.makeText(this, "Twitter app isn't found", Toast.LENGTH_LONG).show();
}