Android 自定义View (二) 进阶

2019-11-08 00:07:20

字体：大中小

来源：转载

供稿：网友

转自: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:

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：