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前言

今天是活动的最后一天啦，后面更文节奏可以舒缓一些了，每篇文章的篇幅也会长些许。废话不多说，我们继续看Handler类。

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。

从源码与官方文档看之Handler篇（八）

前言

正篇

总结