Android阶教程(四)之-Android 中自定义属性(attr.xml,TypedArray)的使用

Android高手进阶教程(四)之----Android 中自定义属性(attr.xml,TypedArray)的使用!

今天我们的教程是根据前面一节扩展进行的，如果你没有看,请点击 Android高手进阶教程(三) 查看第三课,这样跟容易方便你的理解!

在xml 文件里定义控件的属性，我们已经习惯了android:attrs="" ,那么我们能不能定义自己的属性能，比如:test:attrs="" 呢？答案是肯定的.

好了我就不卖关子了，直接进入主题。大致以下步骤:

一、在res/values文件下定义一个attrs.xml文件.代码如下:
<?xml version="1.0" encoding="utf-8"?>
<resources>
??? <declare-styleable name="MyView">
??????? <attr name="textColor" format="color" />
??????? <attr name="textSize" format="dimension" />
??? </declare-styleable>
</resources>

二、我们在MyView.java 代码修改如下，其中下面的构造方法是重点，我们获取定义的属性我们R.sytleable.MyView_textColor, 获取方法中后面通常设定默认值(float textSize = a.getDimension(R.styleable.MyView_textSize, 36 ); )，防止我们在xml 文件中没有定义.从而使用默认值!

获取，MyView 就是定义在<declare-styleable name="MyView "></declare-styleable> 里的名字,获取里面属性用名字_ 属性连接起来就可以.TypedArray 通常最后调用 .recycle() 方法，为了保持以后使用该属性一致性！

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public MyView(Context context,AttributeSet attrs)??
??? {??
??????? super(context,attrs);??
??????? mPaint = new Paint();??
??????????
??????? TypedArray a = context.obtainStyledAttributes(attrs,??
??????????????? R.styleable.MyView);??
??????????
??????? int textColor = a.getColor(R.styleable.MyView_textColor,??
??????????????? 0XFFFFFFFF);??
??????? float textSize = a.getDimension(R.styleable.MyView_textSize, 36);??
??????????
??????? mPaint.setTextSize(textSize);??
??????? mPaint.setColor(textColor);??
??????????
??????? a.recycle();??
??? }?
public MyView(Context context,AttributeSet attrs)
?{
??super(context,attrs);
??mPaint = new Paint();
??
??TypedArray a = context.obtainStyledAttributes(attrs,
????R.styleable.MyView);
??
??int textColor = a.getColor(R.styleable.MyView_textColor,
????0XFFFFFFFF);
??float textSize = a.getDimension(R.styleable.MyView_textSize, 36);
??
??mPaint.setTextSize(textSize);
??mPaint.setColor(textColor);
??
??a.recycle();
?}

MyView.java 全部代码如下:

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package com.android.tutor;??
import android.content.Context;??
import android.content.res.TypedArray;??
import android.graphics.Canvas;??
import android.graphics.Color;??
import android.graphics.Paint;??
import android.graphics.Rect;??
import android.graphics.Paint.Style;??
import android.util.AttributeSet;??
import android.view.View;??
public class MyView extends View {??
??? private Paint mPaint;??
??? private Context mContext;??
??? private static final String mString = "Welcome to Mr Wei's blog";??
??????
??? public MyView(Context context) {??
??????? super(context);??
??????? mPaint = new Paint();??
??? }??
??? public MyView(Context context,AttributeSet attrs)??
??? {??
??????? super(context,attrs);??
??????? mPaint = new Paint();??
??????????
??????? TypedArray a = context.obtainStyledAttributes(attrs,??
??????????????? R.styleable.MyView);??
??????????
??????? int textColor = a.getColor(R.styleable.MyView_textColor,??
??????????????? 0XFFFFFFFF);??
??????? float textSize = a.getDimension(R.styleable.MyView_textSize, 36);??
??????????
??????? mPaint.setTextSize(textSize);??
??????? mPaint.setColor(textColor);??
??????????
??????? a.recycle();??
??? }??
??? @Override?
??? protected void onDraw(Canvas canvas) {??
??????? // TODO Auto-generated method stub??
??????? super.onDraw(canvas);??
??????? //设置填充??
??????? mPaint.setStyle(Style.FILL);??
??????????
??????? //画一个矩形,前俩个是矩形左上角坐标，后面俩个是右下角坐标??
??????? canvas.drawRect(new Rect(10, 10, 100, 100), mPaint);??
??????????
??????? mPaint.setColor(Color.BLUE);??
??????? //绘制文字??
??????? canvas.drawText(mString, 10, 110, mPaint);??
??? }??
}?
package com.android.tutor;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.view.View;
public class MyView extends View {
?private Paint mPaint;
?private Context mContext;
?private static final String mString = "Welcome to Mr Wei's blog";
?
?public MyView(Context context) {
??super(context);
??mPaint = new Paint();
?}
?public MyView(Context context,AttributeSet attrs)
?{
??super(context,attrs);
??mPaint = new Paint();
??
??TypedArray a = context.obtainStyledAttributes(attrs,
????R.styleable.MyView);
??
??int textColor = a.getColor(R.styleable.MyView_textColor,
????0XFFFFFFFF);
??float textSize = a.getDimension(R.styleable.MyView_textSize, 36);
??
??mPaint.setTextSize(textSize);
??mPaint.setColor(textColor);
??
??a.recycle();
?}
?@Override
?protected void onDraw(Canvas canvas) {
??// TODO Auto-generated method stub
??super.onDraw(canvas);
??//设置填充
??mPaint.setStyle(Style.FILL);
??
??//画一个矩形,前俩个是矩形左上角坐标，后面俩个是右下角坐标
??canvas.drawRect(new Rect(10, 10, 100, 100), mPaint);
??
??mPaint.setColor(Color.BLUE);
??//绘制文字
??canvas.drawText(mString, 10, 110, mPaint);
?}
}
?

三、将我们自定义的MyView 加入布局main.xml 文件中，平且使用自定义属性,自定义属性必须加上:

????? xmlns:test ="http://schemas.android.com/apk/res/com.android.tutor "蓝色是自定义属性的前缀，红色是我们包名.

main.xml 全部代码如下:

view plaincopy to clipboardprint?
<?xml???
version="1.0" encoding="utf-8"?>??
<LinearLayout???
xmlns:android="http://schemas.android.com/apk/res/android"?
????????????????
xmlns:test="http://schemas.android.com/apk/res/com.android.tutor"?
??? android:orientation="vertical"?
??? android:layout_width="fill_parent"?
??? android:layout_height="fill_parent"?
??? >??
<TextView????
??? android:layout_width="fill_parent"???
??? android:layout_height="wrap_content"???
??? android:text="@string/hello"?
??? />??
<com.android.tutor.MyView??
??? android:layout_width="fill_parent"???
??? android:layout_height="fill_parent"???
??? test:textSize="20px"?
??? test:textColor="#fff"?
/>??
</LinearLayout>?
<?xml
version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
?????????????
xmlns:test="http://schemas.android.com/apk/res/com.android.tutor"
??? android:orientation="vertical"
??? android:layout_width="fill_parent"
??? android:layout_height="fill_parent"
??? >
<TextView?
??? android:layout_width="fill_parent"
??? android:layout_height="wrap_content"
??? android:text="@string/hello"
??? />
<com.android.tutor.MyView
?android:layout_width="fill_parent"
??? android:layout_height="fill_parent"
??? test:textSize="20px"
??? test:textColor="#fff"
/>
</LinearLayout>
?

四、运行之效果如下图:

今天就到此结束，大家有什么疑问的，请留言，我会及时答复大家!谢谢~

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/Android_Tutor/archive/2010/04/20/5508615.aspx

Android阶教程(四)之-Android 中自定义

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