android 算定义布局xml

引用:http://abc20899.iteye.com/blog/1396565

<com.android.launcher2.DragLayer 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:launcher="http://schemas.android.com/apk/res/com.android.launcher" 
  
    android:id="@+id/drag_layer" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 
  
    <include layout="@layout/all_apps" /> 
  
    <!-- The workspace contains 3 screens of cells --> 
    <com.android.launcher2.Workspace 
        android:id="@+id/workspace" 
        android:layout_width="match_parent" 
        android:layout_height="match_parent" 
        android:scrollbars="horizontal" 
        android:fadeScrollbars="true" 
        launcher:defaultScreen="2"> 
注意到其中的两处: 
xmlns:launcher=”http://schemas.android.com/apk/res/com.android.launcher” 
和 
launcher:defaultScreen="2" 
可以看出在这个布局文件中,使用了自定义属性。 

以前没遇到过,既然这里碰到了,就顺便学习下,下面就写个简单的示例,权当学习笔记,便于以后查阅。 
1. 定义一些自定义属性 
建立一个属性xml文件: values/attrs.xml, 内容如下: 

<?xml version="1.0" encoding="utf-8" ?> 
<resources> 
    <!-- the relation between the icon and text. --> 
    <attr name="relation"> 
        <enum name="icon_left"     value="0" /> 
        <enum name="icon_right"    value="1" /> 
        <enum name="icon_above"    value="2" /> 
        <enum name="icon_below"    value="3" /> 
    </attr> 
      
    <skip /> 
      
    <declare-styleable name="IconText"> 
         <attr name="relation" /> 
         <attr name="icon"         format="reference" /> 
         <attr name="text"         format="string" /> 
       <attr name="text_size"     format="dimension" /> 
       <attr name="text_color"    format="integer" /> 
       <attr name="space"         format="dimension" /> 
    </declare-styleable> 
      
</resources> 
解释如下: 
属性relation有4种可选值:icon_left, icon_right, icon_above,icon_below. 
属性icon的可选值为引用: 例如:"@/drawbable/icon". 
属性text的可选值为string, 例如: "Hello world", 也可是string的引用"@string/hello". 
属性text_size的可选值为尺寸大小,例如:20sp、18dip、20px等. 
属性text_color的可选值为整数,例如:"0xfffffff", 也可以是color的引用"@color/white". 

2. 定义一个能够处理这些属性值的view或者layout类 
package com.braincol.viewattrs; 
  
  
import android.content.Context; 
import android.content.res.TypedArray; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.widget.ImageView; 
import android.widget.LinearLayout; 
import android.widget.TextView; 
  
public class IconTextView  extends LinearLayout { 
    private final static String TAG = "IconTextView"; 
    private final int ICON_LEFT = 0; 
    private final int ICON_RIGHT = 1; 
    private final int ICON_ABOVE = 2; 
    private final int ICON_BELOW = 3; 
  
    private TextView mTextView; 
    private ImageView mImageView; 
  
    private int mRelation = ICON_LEFT; 
    private String mText = ""; 
    private int mIconId; 
    private float mTextSize; 
    private int mSpace; 
  
    public IconTextView(Context context, AttributeSet attrs){ 
        super(context, attrs); 
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.IconText); 
  
        mRelation = a.getInt(R.styleable.IconText_relation, ICON_LEFT); 
        Log.d(TAG,"mRelation: "+mRelation); 
  
        mText = a.getString(R.styleable.IconText_text); 
        Log.d(TAG,"mText: "+mText); 
  
        mTextSize = a.getDimensionPixelSize(R.styleable.IconText_text_size, 12); 
        Log.d(TAG,"mTextSize: "+mTextSize); 
  
        mSpace = a.getDimensionPixelSize(R.styleable.IconText_space, 5); 
        Log.d(TAG,"mSpace: "+mSpace); 
  
        mIconId = a.getResourceId(R.styleable.IconText_icon, R.drawable.icon); 
        Log.d(TAG,"mIconId: "+mIconId); 
  
        a.recycle(); 
  
        mTextView = new TextView(context); 
        mTextView.setText(mText); 
        mTextView.setTextSize(mTextSize); 
  
        mImageView = new ImageView(context); 
        mImageView.setImageResource(mIconId);   
  
        int left    = 0; 
        int top     = 0; 
        int right    = 0; 
        int bottom    = 0; 
        int orientation = HORIZONTAL; 
        int textViewIndex = 0; 
        switch(mRelation){ 
        case ICON_ABOVE: 
            orientation = VERTICAL; 
            bottom = mSpace; 
            textViewIndex = 1; 
            break; 
        case ICON_BELOW: 
            orientation = VERTICAL; 
            top = mSpace; 
            break; 
        case ICON_LEFT: 
            right = mSpace; 
            textViewIndex = 1; 
            break; 
        case ICON_RIGHT: 
            left = mSpace; 
            break; 
        } 
        this.setOrientation(orientation); 
        this.addView(mImageView); 
        mImageView.setPadding(left, top, right, bottom); 
        this.addView(mTextView, textViewIndex); 
    } 

可以看出这个LinearLayout 子类IconTextView中只有两个元素,ImageView 和mTextView,通过从xml配置文件中读取属性值来决定icon和text的内容、相对位置及其它属性。 

3. 在layout布局文件中使用这个自定布局及其属性 
layout/main.xml: 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    > 
<com.braincol.viewattrs.IconTextView 
    android:id="@+id/icontext_01" 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:icontext="http://schemas.android.com/apk/res/com.braincol.viewattrs" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    icontext:relation="icon_left" 
    icontext:icon="@drawable/hi" 
    icontext:text="hi,how are you!" 
    icontext:text_size="12sp" 
  /> 
    
</LinearLayout> 
可以看到我们在这个布局文件中加入了一个新的命名空间: 
xmlns:icontext="http://schemas.android.com/apk/res/com.braincol.viewattrs" 
并使用我们自定义的那些属性: 
icontext:relation="icon_left" 
icontext:icon="@drawable/hi" 
icontext:text="hi, how are you !" 
icontext:text_size="30sp" 
4. 在Activity中使用该布局 

package com.braincol.viewattrs; 
  
import android.app.Activity; 
import android.os.Bundle; 
  
public class ViewAttrs extends Activity { 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
    } 
}

posted @ 2012-07-18 09:35  镇水古月  阅读(133)  评论(0编辑  收藏  举报