Android 自定义View (二) 进阶

出处：http://blog.csdn.net/lmj623565791/article/details/24300125

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：