问题回顾：

在Android8.0手机上不能直接安装Apk，需要权限申请，回调后执行onActivityResult()方法，并弹出对应的dialog，这时需要判断当前Activity是否处于resume状态，通过变量来控制，但结果是这个dialog并不会弹出。

问题本质

Activity跳转到系统应用后回调onActivityResult() 先执行还是onResume()先执行？

查看源码

 /**
     * Called when an activity you launched exits, giving you the requestCode
     * you started it with, the resultCode it returned, and any additional
     * data from it.  The <var>resultCode</var> will be
     * {@link #RESULT_CANCELED} if the activity explicitly returned that,
     * didn't return any result, or crashed during its operation.
     *
     * <p>You will receive this call immediately before onResume() when your
     * activity is re-starting.
     *
     * <p>This method is never invoked if your activity sets
     * {@link android.R.styleable#AndroidManifestActivity_noHistory noHistory} to
     * <code>true</code>.
     *
     * @param requestCode The integer request code originally supplied to
     *                    startActivityForResult(), allowing you to identify who this
     *                    result came from.
     * @param resultCode The integer result code returned by the child activity
     *                   through its setResult().
     * @param data An Intent, which can return result data to the caller
     *               (various data can be attached to Intent "extras").
     *
     * @see #startActivityForResult
     * @see #createPendingResult
     * @see #setResult(int)
     */
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    }

onActivityResult()注释中有这么一句话：

You will receive this call immediately before onResume() when your activity is re-starting.

(意思是说当你的Activity重新启动时 onActivityResult() 会在onResume()之前执行）

很显然，如果你的Activity 调用了 startActivityForResult() 方法启动，回调之后会先执行 onActivityResult() ,然后执行onResume()