Android 自定义View (二) 进阶

转载请标明出处：http://blog.csdn.net/lmj623565791/article/details/24300125

继续自定义View之旅，前面已经介绍过一个自定义View的基础的例子，Android 自定义View (一)，如果你还对自定义View不了解可以去看看。今天给大家带来一个稍微复杂点的例子。

自定义View显示一张图片，下面包含图片的文本介绍，类似相片介绍什么的，不过不重要，主要是学习自定义View的用法么。

还记得上一篇讲的4个步骤么:

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

直接切入正题：

1、在res/values/attr.xml

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

    <attr name="titleText" format="string" />
    <attr name="titleTextSize" format="dimension" />
    <attr name="titleTextColor" format="color" />
    <attr name="image" format="reference" />
    <attr name="imageScaleType">
        <enum name="fillXY" value="0" />
        <enum name="center" value="1" />
    </attr>

    <declare-styleable name="CustomImageView">
        <attr name="titleText" />
        <attr name="titleTextSize" />
        <attr name="titleTextColor" />
        <attr name="image" />
        <attr name="imageScaleType" />
    </declare-styleable>

</resources>

2、在构造中获得我们的自定义属性：

/**
     * 初始化所特有自定义类型
     *
     * @param context
     * @param attrs
     * @param defStyle
     */
    public CustomImageView(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);

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

        int n = a.getIndexCount();

        for (int i = 0; i < n; i++)
        {
            int attr = a.getIndex(i);

            switch (attr)
            {
            case R.styleable.CustomImageView_image:
                mImage = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
                break;
            case R.styleable.CustomImageView_imageScaleType:
                mImageScale = a.getInt(attr, 0);
                break;
            case R.styleable.CustomImageView_titleText:
                mTitle = a.getString(attr);
                break;
            case R.styleable.CustomImageView_titleTextColor:
                mTextColor = a.getColor(attr, Color.BLACK);
                break;
            case R.styleable.CustomImageView_titleTextSize:
                mTextSize = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
                        16, getResources().getDisplayMetrics()));
                break;

            }
        }
        a.recycle();
        rect = new Rect();
        mPaint = new Paint();
        mTextBound = new Rect();
        mPaint.setTextSize(mTextSize);
        // 计算了描绘字体需要的范围
        mPaint.getTextBounds(mTitle, 0, mTitle.length(), mTextBound);

    }

3、重写onMeasure

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
    // super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    /**
     * 设置宽度
     */
    int specMode = MeasureSpec.getMode(widthMeasureSpec);
    int specSize = MeasureSpec.getSize(widthMeasureSpec);

    if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
    {
        Log.e("xxx", "EXACTLY");
        mWidth = specSize;
    } else
    {
        // 由图片决定的宽
        int desireByImg = getPaddingLeft() + getPaddingRight() + mImage.getWidth();
        // 由字体决定的宽
        int desireByTitle = getPaddingLeft() + getPaddingRight() + mTextBound.width();

        if (specMode == MeasureSpec.AT_MOST)// wrap_content
        {
            int desire = Math.max(desireByImg, desireByTitle);
            mWidth = Math.min(desire, specSize);
            Log.e("xxx", "AT_MOST");
        }
    }

    /***
     * 设置高度
     */

    specMode = MeasureSpec.getMode(heightMeasureSpec);
    specSize = MeasureSpec.getSize(heightMeasureSpec);
    if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
    {
        mHeight = specSize;
    } else
    {
        int desire = getPaddingTop() + getPaddingBottom() + mImage.getHeight() + mTextBound.height();
        if (specMode == MeasureSpec.AT_MOST)// wrap_content
        {
            mHeight = Math.min(desire, specSize);
        }
    }
    setMeasuredDimension(mWidth, mHeight);

}

4、重写onDraw

@Override
    protected void onDraw(Canvas canvas)
    {
        // super.onDraw(canvas);
        /**
         * 边框
         */
        mPaint.setStrokeWidth(4);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.CYAN);
        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);

        rect.left = getPaddingLeft();
        rect.right = mWidth - getPaddingRight();
        rect.top = getPaddingTop();
        rect.bottom = mHeight - getPaddingBottom();

        mPaint.setColor(mTextColor);
        mPaint.setStyle(Style.FILL);
        /**
         * 当前设置的宽度小于字体需要的宽度，将字体改为xxx...
         */
        if (mTextBound.width() > mWidth)
        {
            TextPaint paint = new TextPaint(mPaint);
            String msg = TextUtils.ellipsize(mTitle, paint, (float) mWidth - getPaddingLeft() - getPaddingRight(),
                    TextUtils.TruncateAt.END).toString();
            canvas.drawText(msg, getPaddingLeft(), mHeight - getPaddingBottom(), mPaint);

        } else
        {
            //正常情况，将字体居中
            canvas.drawText(mTitle, mWidth / 2 - mTextBound.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);
        }

        //取消使用掉的快
        rect.bottom -= mTextBound.height();

        if (mImageScale == IMAGE_SCALE_FITXY)
        {
            canvas.drawBitmap(mImage, null, rect, mPaint);
        } else
        {
            //计算居中的矩形范围
            rect.left = mWidth / 2 - mImage.getWidth() / 2;
            rect.right = mWidth / 2 + mImage.getWidth() / 2;
            rect.top = (mHeight - mTextBound.height()) / 2 - mImage.getHeight() / 2;
            rect.bottom = (mHeight - mTextBound.height()) / 2 + mImage.getHeight() / 2;

            canvas.drawBitmap(mImage, null, rect, mPaint);
        }

    }

代码，结合注释和第一篇View的使用，应该可以看懂，不明白的留言。下面我们引入我们的自定义View:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:zhy="http://schemas.android.com/apk/res/com.zhy.customview02"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <com.zhy.customview02.view.CustomImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:padding="10dp"
        zhy:image="@drawable/ic_launcher"
        zhy:imageScaleType="center"
        zhy:titleText="hello andorid ! "
        zhy:titleTextColor="#ff0000"
        zhy:titleTextSize="30sp" />

    <com.zhy.customview02.view.CustomImageView
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:padding="10dp"
        zhy:image="@drawable/ic_launcher"
        zhy:imageScaleType="center"
        zhy:titleText="helloworldwelcome"
        zhy:titleTextColor="#00ff00"
        zhy:titleTextSize="20sp" />

    <com.zhy.customview02.view.CustomImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:padding="10dp"
        zhy:image="@drawable/lmj"
        zhy:imageScaleType="center"
        zhy:titleText="妹子~"
        zhy:titleTextColor="#ff0000"
        zhy:titleTextSize="12sp" />

</LinearLayout>

我特意让显示出现3中情况：

1、字体的宽度大于图片，且View宽度设置为wrap_content

2、View宽度设置为精确值，字体的长度大于此宽度

3、图片的宽度大于字体，且View宽度设置为wrap_content

看看显示效果：

怎么样，对于这三种情况所展示的效果都还不错吧。