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" > < 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); } } |
运行效果:
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" > < 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); } } |
运行效果: