AndroidStudio中如何在android style文件中使用自定义属性

今天在看android froyo的launcher2 源码的时候，在launcher.xml中看到有这么一段代码：

<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">

 

    <includelayout="@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：

<?xmlversion="1.0" encoding="utf-8" ?>

<resources>

    <!-- the relation between the icon and text. -->

    <attrname="relation">

        <enumname="icon_left"     value="0" />

        <enumname="icon_right"    value="1" />

        <enumname="icon_above"    value="2" />

        <enumname="icon_below"    value="3" />

    </attr>

     

    <skip/>

     

    <declare-styleablename="IconText">

         <attrname="relation" />

         <attrname="icon"         format="reference" /> 

         <attrname="text"         format="string" />

       <attrname="text_size"     format="dimension" />

       <attrname="text_color"    format="integer" />

       <attrname="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  extendsLinearLayout {

    privatefinal static String TAG = "IconTextView";

    privatefinal int ICON_LEFT = 0;

    privatefinal int ICON_RIGHT = 1;

    privatefinal int ICON_ABOVE = 2;

    privatefinal int ICON_BELOW = 3;

 

    privateTextView mTextView;

    privateImageView mImageView;

 

    privateint mRelation = ICON_LEFT;

    privateString mText = "";

    privateint mIconId;

    privatefloat mTextSize;

    privateint mSpace;

 

    publicIconTextView(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);   

 

        intleft    = 0;

        inttop     = 0;

        intright    = 0;

        intbottom    = 0;

        intorientation = HORIZONTAL;

        inttextViewIndex = 0;

        switch(mRelation){

        caseICON_ABOVE:

            orientation = VERTICAL;

            bottom = mSpace;

            textViewIndex =1;

            break;

        caseICON_BELOW:

            orientation = VERTICAL;

            top = mSpace;

            break;

        caseICON_LEFT:

            right = mSpace;

            textViewIndex =1;

            break;

        caseICON_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:

<?xmlversion="1.0" encoding="utf-8"?>

<LinearLayoutxmlns: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 extendsActivity {

    /** Called when the activity is first created. */

    @Override

    publicvoid onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

    }

}

运行效果：