1.隐式意图
怎么传值我就不细说了，说些一般人不知道的吧。
1）Verify There is an App to Receive the Intent（判断是否有App响应了意图）
you should always include a
verification step before invoking an intent.
Caution: If you invoke an intent and there is no app
available on the device that can handle the intent, your app will crash.（没有应用处理意图，应用就会挂掉。）
因为你不能保证每个手机上都有你需要的应用!
PackageManager packageManager =getPackageManager();
List activities = packageManager.queryIntentActivities(intent,
PackageManager.MATCH_DEFAULT_ONLY);
boolean isIntentSafe = activities.size() > 0;
If isIntentSafe is true, then at least one app will respond to
the intent. If it is
false, then there aren't any apps to handle the intent.
2）
