Android中自定义属性（attrs.xml,TypedArray的使用）

最新推荐文章于 2021-11-23 17:29:25 发布

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最新推荐文章于 2021-11-23 17:29:25 发布

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分类专栏： android应用文章标签： android

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本文介绍如何在Android中创建自定义View，并实现个性化的属性设置。通过详细步骤讲解自定义属性的定义方法，包括使用attrs.xml文件及TypedArray类等关键技术点。此外，还提供了完整的代码示例。

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很多的时候，android的自带的控件不能满足我们的需求，需要进行自定义view,同时自定义属性，方便自定义view的个性化设计和代码管理，下面简单的介绍一下自定义属性：

一、TypedArray类

android.content.res.TypedArray
obtainStyledAttributes(AttributeSet, int[], int, int) 
obtainAttributes(AttributeSet, int[])

在执行完之后，一定要确保调用 recycle()函数，用于检索从这个结构对应于给定的属性位置到obtainStyledAttributes中的值

/**
     * Give back a previously retrieved StyledAttributes, for later re-use.
     */
    public void recycle() {
        synchronized (mResources.mTmpValue) {
            TypedArray cached = mResources.mCachedStyledAttributes;
            if (cached == null || cached.mData.length < mData.length) {
                mXml = null;
                mResources.mCachedStyledAttributes = this;
            }
        }
    }

二、自定义attrs.xml与原生android属性的对比

1. reference：参考某一资源ID。
（1）属性定义：

            <declare-styleable name = "名称">
                   <attr name = "background" format = "reference" />
            </declare-styleable>

（2）属性使用：

              <ImageView
                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:background = "@drawable/图片ID"
                     />

2. color：颜色值。
（1）属性定义：

            <declare-styleable name = "名称">
                   <attr name = "textColor" format = "color" />
            </declare-styleable>

（2）属性使用：

             <TextView
                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:textColor = "#00FF00"
                     />

3. boolean：布尔值。
（1）属性定义：

            <declare-styleable name = "名称">
                   <attr name = "focusable" format = "boolean" />
            </declare-styleable>

（2）属性使用：

              <Button
                    android:layout_width = "42dip"
                    android:layout_height = "42dip"
                    android:focusable = "true"
                    />

4. dimension：尺寸值。
（1）属性定义：

            <declare-styleable name = "名称">
                   <attr name = "layout_width" format = "dimension" />
            </declare-styleable>

（2）属性使用：

             <Button
                    android:layout_width = "42dip"
                    android:layout_height = "42dip"
                    />

5. float：浮点值。
（1）属性定义：

            <declare-styleable name = "AlphaAnimation">
                   <attr name = "fromAlpha" format = "float" />
                   <attr name = "toAlpha" format = "float" />
            </declare-styleable>

（2）属性使用：

              <alpha
                   android:fromAlpha = "1.0"
                   android:toAlpha = "0.7"
                   />

6. integer：整型值。
（1）属性定义：

           <declare-styleable name = "AnimatedRotateDrawable">
                   <attr name = "visible" />
                   <attr name = "frameDuration" format="integer" />
                   <attr name = "framesCount" format="integer" />
                   <attr name = "pivotX" />
                   <attr name = "pivotY" />
                   <attr name = "drawable" />
            </declare-styleable>

（2）属性使用：

             <animated-rotate
                   xmlns:android = "http://schemas.android.com/apk/res/android" 
                   android:drawable = "@drawable/图片ID" 
                   android:pivotX = "50%" 
                   android:pivotY = "50%" 
                   android:framesCount = "12" 
                   android:frameDuration = "100"
                   />

7. string：字符串。
（1）属性定义：

            <declare-styleable name = "MapView">
                   <attr name = "apiKey" format = "string" />
            </declare-styleable>

（2）属性使用：

              <com.google.android.maps.MapView
                    android:layout_width = "fill_parent"
                    android:layout_height = "fill_parent"
                    android:apiKey = "your key"
                    />

8. fraction：百分数。
（1）属性定义：

             <declare-styleable name="RotateDrawable">
                   <attr name = "visible" />
                   <attr name = "fromDegrees" format = "float" />
                   <attr name = "toDegrees" format = "float" />
                   <attr name = "pivotX" format = "fraction" />
                   <attr name = "pivotY" format = "fraction" />
                   <attr name = "drawable" />
             </declare-styleable>

（2）属性使用：

                <rotate  xmlns:android = "http://schemas.android.com/apk/res/android"
　　             android:interpolator = "@anim/动画ID"
                 android:fromDegrees = "0"
　　             android:toDegrees = "360"
                 android:pivotX = "200%"
                 android:pivotY = "300%"
　　             android:duration = "5000"
                 android:repeatMode = "restart"
                 android:repeatCount = "infinite"
                   />

9. enum：枚举值。
（1）属性定义：

           <declare-styleable name="名称">
                   <attr name="orientation">
                          <enum name="horizontal" value="0" />
                          <enum name="vertical" value="1" />
                   </attr>           
            </declare-styleable>

（2）属性使用：

            <LinearLayout
                    xmlns:android = "http://schemas.android.com/apk/res/android"
                    android:orientation = "vertical"
                    android:layout_width = "fill_parent"
                    android:layout_height = "fill_parent"
                    >
            </LinearLayout>

10. flag：位或运算。
（1）属性定义：

   <span style="white-space:pre">	</span>       <declare-styleable name="名称">
                    <attr name="windowSoftInputMode">
                            <flag name = "stateUnspecified" value = "0" />
                            <flag name = "stateUnchanged" value = "1" />
                            <flag name = "stateHidden" value = "2" />
                            <flag name = "stateAlwaysHidden" value = "3" />
                            <flag name = "stateVisible" value = "4" />
                            <flag name = "stateAlwaysVisible" value = "5" />
                            <flag name = "adjustUnspecified" value = "0x00" />
                            <flag name = "adjustResize" value = "0x10" />
                            <flag name = "adjustPan" value = "0x20" />
                            <flag name = "adjustNothing" value = "0x30" />
                     </attr>        
             </declare-styleable>

（2）属性使用：

             <activity
                   android:name = ".StyleAndThemeActivity"
                   android:label = "@string/app_name"
                   android:windowSoftInputMode = "stateUnspecified | stateUnchanged　|　stateHidden">
                   <intent-filter>
                          <action android:name = "android.intent.action.MAIN" />
                          <category android:name = "android.intent.category.LAUNCHER" />
                   </intent-filter>
             </activity>

另外也可以指定多种类型值。
（1）属性定义：

            <declare-styleable name = "名称">
                   <attr name = "background" format = "reference|color" />
            </declare-styleable>

（2）属性使用：

              <ImageView
                     android:layout_width = "42dip"
                     android:layout_height = "42dip"
                     android:background = "@drawable/图片ID|#00FF00"
                     />

三、实例演示

1、attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="MyView">
        <attr name="textColor" format="color"></attr>
        <attr name="textSize" format="dimension"></attr>
    </declare-styleable>

</resources>

2、my_view_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:myview="http://schemas.android.com/apk/res/cn.jon.demo"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <cn.view.demo.MyView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        myview:textColor="#00ff00"
        myview:textSize="26sp">
    </cn.view.demo.MyView>
</LinearLayout>

3、MyView.java

package cn.view.demo;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import cn.jon.demo.R;

public class MyView extends View {

	private Paint mPaint;

	public MyView(Context context) {
		this(context, null);
	}

	public MyView(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public MyView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);

		initViews(context, attrs);

	}

	private void initViews(Context context, AttributeSet attrs) {

		mPaint = new Paint();
		TypedArray a = context
				.obtainStyledAttributes(attrs, R.styleable.MyView);

		int textColor = a.getColor(R.styleable.MyView_textColor, 0);
		float textSize = a.getDimension(R.styleable.MyView_textSize, 35);
		mPaint.setTextSize(textSize);
		mPaint.setColor(textColor);

		a.recycle();
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		mPaint.setAntiAlias(true);
		canvas.drawCircle(getWidth() / 2, getHeight() / 2, 80, mPaint);
		mPaint.setColor(Color.RED);
		canvas.drawText("circle", getWidth() / 2-40, getHeight() / 2, mPaint);
	
		mPaint.setColor(Color.BLUE);
		mPaint.setStrokeWidth(5);
		
		for (int y =30,alpha=255 ;alpha>2 ; alpha>>=1,y+=10) {
			mPaint.setAlpha(alpha);
			canvas.drawLine(getWidth() / 2-40,getHeight() / 2-y, 100, getHeight() / 2-y, mPaint);
		}
	
	}

}

4、MyActivity.java

package cn.view.demo;

import cn.jon.demo.R;
import android.app.Activity;
import android.os.Bundle;

public class MyActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		//setContentView(new MyView(this));
		setContentView(R.layout.my_view_main);
	}

}

5、运行效果