Android -- 自定义View

步骤

  1. 自定义View的属性
  2. 在View的构造方法中获得我们自定义的属性
  3. 重写onMesure
  4. 重写onDraw

自定义View的属性

在res/values/下建立一个attrs.xml ,在里面定义我们的属性和声明我们的整个样式:

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

<resources>  

  

    <attr name="titleText" format="string" />  

    <attr name="titleTextColor" format="color" />  

    <attr name="titleTextSize" format="dimension" />  

  

    <declare-styleable name="CustomTitleView">  

        <attr name="titleText" />  

        <attr name="titleTextColor" />  

        <attr name="titleTextSize" />  

    </declare-styleable>  

  

</resources>

定义了字体,字体颜色,字体大小3个属性。format是值该属性的取值类型:一共有string,color,demension,integer,enum,reference,float,boolean,fraction,flag

在布局中自定义View

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  

    xmlns:tools="http://schemas.android.com/tools"  

    xmlns:custom="http://schemas.android.com/apk/res-auto"  

    android:layout_width="match_parent"  

    android:layout_height="match_parent" >  

  

    <com.yydcdut.CustomTitleView  

        android:layout_width="200dp"  

        android:layout_height="100dp"  

        custom:titleText="3712"  

        custom:titleTextColor="#ff0000"  

        custom:titleTextSize="40sp" />  

  

</RelativeLayout>

xmlns:custom=http://schemas.android.com/apk/res-auto,命名空间,现在都是res-auto形式的了。

View的构造方法

/** 

     * 文本 

     */  

    private String mTitleText;  

    /** 

     * 文本的颜色 

     */  

    private int mTitleTextColor;  

    /** 

     * 文本的大小 

     */  

    private int mTitleTextSize;  

  

    /** 

     * 绘制时控制文本绘制的范围 

     */  

    private Rect mBound;  

    private Paint mPaint;  

  

    public CustomTitleView(Context context, AttributeSet attrs)  

    {  

        this(context, attrs, 0);  

    }  

  

    public CustomTitleView(Context context)  

    {  

        this(context, null);  

    }  

  

    /** 

     * 获得我自定义的样式属性 

     *  

     * @param context 

     * @param attrs 

     * @param defStyle 

     */  

    public CustomTitleView(Context context, AttributeSet attrs, int defStyle)  

    {  

        super(context, attrs, defStyle);  

        /** 

         * 获得我们所定义的自定义样式属性 

         */  

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomTitleView, defStyle, 0);  

        int n = a.getIndexCount();  

        for (int i = 0; i < n; i++)  

        {  

            int attr = a.getIndex(i);  

            switch (attr)  

            {  

            case R.styleable.CustomTitleView_titleText:  

                mTitleText = a.getString(attr);  

                break;  

            case R.styleable.CustomTitleView_titleTextColor:  

                // 默认颜色设置为黑色  

                mTitleTextColor = a.getColor(attr, Color.BLACK);  

                break;  

            case R.styleable.CustomTitleView_titleTextSize:  

                // 默认设置为16sp,TypeValue也可以把sp转化为px  

                mTitleTextSize = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(  

                        TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));  

                break;  

  

            }  

  

        }  

        a.recycle();  

  

        /** 

         * 获得绘制文本的宽和高 

         */  

        mPaint = new Paint();  

        mPaint.setTextSize(mTitleTextSize);  

        // mPaint.setColor(mTitleTextColor);  

        mBound = new Rect();  

        mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);  

  

    }

我们重写了3个构造方法,默认的布局文件调用的是两个参数的构造方法,所以记得让所有的构造调用我们的三个参数的构造,我们在三个参数的构造中获得自定义属性。

重写onDraw,onMesure

@Override  

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)  

    {  

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);  

    }  

  

    @Override  

    protected void onDraw(Canvas canvas)  

    {  

        mPaint.setColor(Color.YELLOW);  

        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);  

  

        mPaint.setColor(mTitleTextColor);  

        canvas.drawText(mTitleText, getWidth() / 2 - mBound.width() / 2, getHeight() / 2 + mBound.height() / 2, mPaint);  

    }

1

此时长宽都是固定的,当长宽都设置为wrap_content,会发现效果:

2

系统帮我们测量的高度和宽度都是MATCH_PARNET,当我们设置明确的宽度和高度时,系统帮我们测量的结果就是我们设置的结果,当我们设置为WRAP_CONTENT,或者MATCH_PARENT系统帮我们测量的结果就是MATCH_PARENT的长度。

所以,当设置了WRAP_CONTENT时,我们需要自己进行测量,即重写onMesure方法”:

重写之前先了解MeasureSpec的specMode,一共三种类型:

EXACTLY    //一般是设置了明确的值或者是MATCH_PARENT



AT_MOST    //表示子布局限制在一个最大值内,一般为WARP_CONTENT



UNSPECIFIED    //表示子布局想要多大就多大,很少使用

重写onMeasure

@Override  

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)  {  

    int widthMode = MeasureSpec.getMode(widthMeasureSpec);  

    int widthSize = MeasureSpec.getSize(widthMeasureSpec);  

    int heightMode = MeasureSpec.getMode(heightMeasureSpec);  

    int heightSize = MeasureSpec.getSize(heightMeasureSpec);  

    int width;  

    int height ;  

    if (widthMode == MeasureSpec.EXACTLY) {  

        width = widthSize;  

    } else {  

        mPaint.setTextSize(mTitleTextSize);  

        mPaint.getTextBounds(mTitle, 0, mTitle.length(), mBounds);  

        float textWidth = mBounds.width();  

        int desired = (int) (getPaddingLeft() + textWidth + getPaddingRight());  

        width = desired;  

    }  

  

    if (heightMode == MeasureSpec.EXACTLY){  

        height = heightSize;  

    } else {  

        mPaint.setTextSize(mTitleTextSize);  

        mPaint.getTextBounds(mTitle, 0, mTitle.length(), mBounds);  

        float textHeight = mBounds.height();  

        int desired = (int) (getPaddingTop() + textHeight + getPaddingBottom());  

        height = desired;  

    }  

  

    setMeasuredDimension(width, height);  

}

布局修改一下

<com.yydcdut.CustomTitleView  

        android:layout_width="wrap_content"  

        android:layout_height="wrap_content"  

        custom:titleText="3712"  

        android:padding="10dp"  

        custom:titleTextColor="#ff0000"  

        android:layout_centerInParent="true"  

        custom:titleTextSize="40sp" />

3

我是天王盖地虎的分割线

 

 

参考:http://blog.csdn.net/lmj623565791/article/details/24252901

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