Aggiunta di un pulsante sotto una listview su Android

Question

Quindi sto cercando di aggiungere un pulsante sotto un listview in Android, il problema è che il pulsante non viene visualizzato.

<?xml version="1.0" encoding="utf-8"?> 
<AbsoluteLayout 
    android:id="@+id/widget0" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    xmlns:android="http://schemas.android.com/apk/res/android"> 

    <ListView 
     android:id="@+id/messagelist" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_x="0px" 
     android:layout_y="0px"> 
    </ListView> 
    <Button 
     android:id="@+id/addbutton" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="Button" 
     android:layout_x="0px" 
     android:layout_y="379px"> 
    </Button> 
</AbsoluteLayout> 

Answer 1

AbsoluteLayout è obsoleto. Vorrei suggerire, invece di utilizzare un LinearLayout:

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout 
    android:id="@+id/widget0" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    xmlns:android="http://schemas.android.com/apk/res/android"> 

    <ListView 
     android:id="@+id/messagelist" 
     android:layout_width="wrap_content" 
     android:layout_height="0dp" 
     android:layout_weight="1"> 
    </ListView> 
    <Button 
     android:id="@+id/addbutton" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="Button"> 
    </Button> 
</LinearLayout> 

Vorrei anche suggerire la lettura attraverso il developer docs su layout per una buona introduzione.

Answer 2

C'è un esempio di tale layout nell'esempio "Demo API". Le seguenti pagine contengono collegamenti ai campioni:

http://developer.android.com/resources/samples/index.html

cercare il file LinearLayout9.java, e il suo corrispondente linear_layout9.xml file di layout. Per comodità, li ho incollato qui:

LinearLayout9.java:

/* 
* Copyright (C) 2007 The Android Open Source Project 
* 
* Licensed under the Apache License, Version 2.0 (the "License"); 
* you may not use this file except in compliance with the License. 
* You may obtain a copy of the License at 
* 
*  http://www.apache.org/licenses/LICENSE-2.0 
* 
* Unless required by applicable law or agreed to in writing, software 
* distributed under the License is distributed on an "AS IS" BASIS, 
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
* See the License for the specific language governing permissions and 
* limitations under the License. 
*/ 

package com.example.android.apis.view; 

import com.example.android.apis.R; 

import android.app.Activity; 
import android.os.Bundle; 
import android.widget.ListView; 
import android.widget.ArrayAdapter; 

/** 
* Demonstrates how the layout_weight attribute can shrink an element too big 
* to fit on screen. 
*/ 
public class LinearLayout9 extends Activity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.linear_layout_9); 
     ListView list = (ListView) findViewById(R.id.list); 
     list.setAdapter(new ArrayAdapter<String>(this, 
       android.R.layout.simple_list_item_1, AutoComplete1.COUNTRIES)); 
    } 

} 

linear_layout9.xml:

<?xml version="1.0" encoding="utf-8"?> 
<!-- Copyright (C) 2007 The Android Open Source Project 

    Licensed under the Apache License, Version 2.0 (the "License"); 
    you may not use this file except in compliance with the License. 
    You may obtain a copy of the License at 

      http://www.apache.org/licenses/LICENSE-2.0 

    Unless required by applicable law or agreed to in writing, software 
    distributed under the License is distributed on an "AS IS" BASIS, 
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
    See the License for the specific language governing permissions and 
    limitations under the License. 
--> 

<!-- 
    Demonstrates a simple linear layout. The layout fills the screen, with the 
    children stacked from the top. 
    --> 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

    <ListView android:id="@+id/list" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_weight="1.0" /> 

    <Button 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:text="@string/linear_layout_9_button" /> 

</LinearLayout>