XML : Organizing layouts with edit text at bottom?

I wanted to make a layout with 3 LinearLayouts. In the 2nd LinearLayout I would have a ListView and the 3rd LinearLayout I would have an EditText and Button at the bottom. This was my attempt:

  <?xml version="1.0" encoding="utf-8"?>  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"      xmlns:fresco="http://schemas.android.com/apk/res-auto"      android:orientation="vertical"      android:layout_width="match_parent"      android:layout_height="match_parent">        <LinearLayout          android:id="@+id/view_post"          android:layout_width="fill_parent"          android:layout_height="200dp"          android:background="@color/com_facebook_blue">            <TextView              android:layout_width="fill_parent"              android:layout_height="wrap_content"              android:id="@+id/view_status"/>        </LinearLayout>            <LinearLayout              android:id="@+id/view_comments"              android:layout_below="@+id/view_post"              android:layout_width="match_parent"              android:layout_height="250dp">                <ListView                  android:id="@+id/lv_comments_feed"                  android:layout_width="fill_parent"                  android:layout_height="wrap_content">              </ListView>            </LinearLayout>            <LinearLayout              android:layout_below="@+id/view_comments"              android:id="@+id/send_message"              android:layout_width="match_parent"              android:layout_height="50dp"              android:layout_alignParentBottom="true"              android:orientation="horizontal" >                <EditText                  android:id="@+id/write_comment"                  android:layout_width="0dp"                  android:layout_height="wrap_content"                  android:layout_gravity="center_vertical|center_horizontal"                  android:layout_weight="5"                  android:gravity="top|left"                  android:inputType="textMultiLine"                  android:scrollHorizontally="false" />                <Button                  android:id="@+id/send_comment"                  android:layout_width="wrap_content"                  android:layout_height="wrap_content"                  android:layout_gravity="center_vertical|center_horizontal"                  android:gravity="center"                  android:text="send"                  android:textAppearance="?android:attr/textAppearanceMedium" />          </LinearLayout>    </RelativeLayout>    

Now the design looks great but when I load the app on my phone, I have 2 problems:

1. I don't want to hardcode the LinearLayout heights. I have looked into layout_weight but I can't seem to have these layout_weights work without running into the 2nd problem below:

2. When I click the EditText, the EditText is hidden even though I have declared android:windowSoftInputMode="adjustResize|stateHidden" in my activity and I'm not sure why that's happening. Also, the EditText and Button are not directly at the bottom of the screen which is what I would want. Any help is appreciated, thanks!