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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);   } 

Android -- 自定义View

此时长宽都是固定的,当长宽都设置为wrap_content,会发现效果:

Android -- 自定义View

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" />

Android -- 自定义View

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

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