正篇
上一篇我们看了不带参数的obtainMessage方法，现在我们来看看带参的：
/** * Same as {@link #obtainMessage()}, except that it also sets the what member of the returned Message. * * @param what Value to assign to the returned Message.what field. * @return A Message from the global message pool. */ @NonNull public final Message obtainMessage(int what) { return Message.obtain(this, what); }
该方法的参数what是分配给返回的 Message.what 字段的值，通俗来说就是message对象的key、名称，当然这个方法和obtainMessage()一样，是返回一个从全局消息池中的Message对象。 接下来的方法又在此基础上增加了一个参数@Nullable Object obj，即一个不为空的对象obj 成员：
/** * * Same as {@link #obtainMessage()}, except that it also sets the what and obj members * of the returned Message. * * @param what Value to assign to the returned Message.what field. * @param obj Value to assign to the returned Message.obj field. * @return A Message from the global message pool. */ @NonNull public final Message obtainMessage(int what, @Nullable Object obj) { return Message.obtain(this, what, obj); }
此外，还有两个带参obtainMessage方法：
/** * * Same as {@link #obtainMessage()}, except that it also sets the what, arg1 and arg2 members of the returned * Message. * @param what Value to assign to the returned Message.what field. * @param arg1 Value to assign to the returned Message.arg1 field. * @param arg2 Value to assign to the returned Message.arg2 field. * @return A Message from the global message pool. */ @NonNull public final Message obtainMessage(int what, int arg1, int arg2) { return Message.obtain(this, what, arg1, arg2); } /** * * Same as {@link #obtainMessage()}, except that it also sets the what, obj, arg1,and arg2 values on the * returned Message. * @param what Value to assign to the returned Message.what field. * @param arg1 Value to assign to the returned Message.arg1 field. * @param arg2 Value to assign to the returned Message.arg2 field. * @param obj Value to assign to the returned Message.obj field. * @return A Message from the global message pool. */ @NonNull public final Message obtainMessage(int what, int arg1, int arg2, @Nullable Object obj) { return Message.obtain(this, what, arg1, arg2, obj); }
通过带不同的参数去获取不同的消息，该方法到此结束。
（未完待续）
总结
今天主要将obtainMessage方法看完，下一次将去看我们安卓使用较为常见也是Handler极为重要的方法post()方法，去体会不同的post方法的功能与官方所给的注释大意。
