Thinking in Google Doc-不同的Apps之间的交互

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）