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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

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:

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。

好了，就到这里，各位看官，没事留个言，顶一个呗~

Android 自定义View (二) 进阶

源码点击下载