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:

[java]
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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>

[java]
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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:

[java]
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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);
}
}

[java]
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<?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>