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[操作系统]Android自定义View初步


  经过上一篇的介绍,大家对于自定义View一定有了一定的认识,接下来我们就以实现一个图片下显示文字的自定义View来练习一下。废话不多说,下面进入我们的正题,首先看一下我们的思路,1、我们需要通过在values文件夹下添加一个attrs的文件,里面设置我们的自定义属性;2、通过重写View类,来获得我们设置的自定义属性的参数,并进行绘制;3、在我们的视图文件中进行引用。好了到这里我们的基本思路就已经形成,下面我们开始进行我们的实战编码操作。

  第一步:在res目录下,values文件夹下,新建一个attrs.

<?"1.0" encoding="utf-8"?><resources>    <attr name="TitleText" format="string" />  <attr name="TitleColor" format="color" />  <attr name="TitleSize" format="dimension" />    <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="TitleColor" />     <attr name="TitleSize" />    <attr name="image" />    <attr name="imageScaleType" />  </declare-styleable>  </resources>

  提示一下:format对应的是该参数的值类型

  第二步:重写我们的View类:

public class MySelfImageView extends View {    /*   * 图片区域   */  Rect imageRect;  /*   * 文字区域   */  Rect titleRect;  /*   * 画笔对象   */  Paint mPaint;  /*   * 图片标题文字   */  String titleText;  /*   * 图片标题文字颜色   */  int titleColor;  /*   * 图片标题文字大小   */  int titleSize;  /*   * 图片资源   */  Bitmap image;  /*   * 图片资源显示样式   */  int imageFillXY;    int mWidth = 0;  int mHeight = 0;    public MySelfImageView(Context context) {    this(context, null);  }  public MySelfImageView(Context context, AttributeSet attrs) {    this(context, attrs, 0);  }  public MySelfImageView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    //获取自定义设置的属性    TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyleAttr, 0);    int n = typedArray.getIndexCount();    for(int i=0; i<n; i++){      int att = typedArray.getIndex(i);      //分别取出自定义属性设置的值      switch (att) {        case R.styleable.CustomImageView_TitleText:          titleText = typedArray.getString(att);          break;        case R.styleable.CustomImageView_TitleColor:          titleColor = typedArray.getColor(att, Color.RED);              break;        case R.styleable.CustomImageView_TitleSize:          titleSize = typedArray.getDimensionPixelSize(att, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,               16, getResources().getDisplayMetrics()));           break;        case R.styleable.CustomImageView_image:          image = BitmapFactory.decodeResource(getResources(), typedArray.getResourceId(att, 0));          break;        case R.styleable.CustomImageView_imageScaleType:          imageFillXY = typedArray.getInt(att, 0);          break;      }    }    typedArray.recycle();        imageRect = new Rect();    mPaint = new Paint();    titleRect = new Rect();    mPaint.setTextSize(titleSize);    // 计算描绘字体需要的范围    mPaint.getTextBounds(titleText, 0, titleText.length(), titleRect);  }    @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    /**     * 设置宽度     */    int specMode = MeasureSpec.getMode(widthMeasureSpec);    int specSize = MeasureSpec.getSize(widthMeasureSpec);        if(specMode == MeasureSpec.EXACTLY){      mWidth = specSize;    }else{      // 由图片决定的宽       int desireByImg = getPaddingLeft() + getPaddingRight() + image.getWidth();       // 由字体决定的宽       int desireByTitle = getPaddingLeft() + getPaddingRight() + titleRect.width();          if (specMode == MeasureSpec.AT_MOST){// wrap_content         int desire = Math.max(desireByImg, desireByTitle);        mWidth = Math.min(desire, specSize);      }     }        /**     * 设置高度     */    specMode = MeasureSpec.getMode(heightMeasureSpec);    specSize = MeasureSpec.getSize(heightMeasureSpec);        if(specMode == MeasureSpec.EXACTLY){      mHeight = specSize;    }else{      int desire = getPaddingTop() + getPaddingBottom() + image.getHeight() + titleRect.height();       if (specMode == MeasureSpec.AT_MOST){// wrap_content         mHeight = Math.min(desire, specSize);      }     }    setMeasuredDimension(mWidth, mHeight);  }    @Override  protected void onDraw(Canvas canvas) {    /**     * 边框     */     mPaint.setStrokeWidth(4);//设置空心线宽     mPaint.setStyle(Paint.Style.STROKE);//设置画笔为空心     mPaint.setColor(Color.CYAN);//设置画笔颜色     canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);      imageRect.left = getPaddingLeft();     imageRect.right = mWidth - getPaddingRight();     imageRect.top = getPaddingTop();     imageRect.bottom = mHeight - getPaddingBottom();      mPaint.setColor(titleColor);     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 (titleRect.width() > mWidth) {       TextPaint paint = new TextPaint(mPaint);       String msg = TextUtils.ellipsize(titleText, 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(titleText, mWidth / 2 - titleRect.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);    }      //取消使用掉的块     imageRect.bottom -= titleRect.height();      if (imageFillXY == 0) {      canvas.drawBitmap(image, null, imageRect, mPaint);     } else {       //计算居中的矩形范围       imageRect.left = mWidth / 2 - image.getWidth() / 2;       imageRect.right = mWidth / 2 + image.getWidth() / 2;       imageRect.top = (mHeight - titleRect.height()) / 2 - image.getHeight() / 2;       imageRect.bottom = (mHeight - titleRect.height()) / 2 + image.getHeight() / 2;        canvas.drawBitmap(image, null, imageRect, mPaint);     }   }}

  第三步:布局文件

<LinearLayout   ="http://schemas.android.com/apk/res/com.example.myselfview"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical" >    <com.example.myselfview.view.MySelfImageView     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:TitleColor="#ff0000"     zhy:TitleSize="30sp" />    <com.example.myselfview.view.MySelfImageView     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:TitleColor="#00ff00"     zhy:TitleSize="20sp" />    <com.example.myselfview.view.MySelfImageView     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_margin="10dp"     android:padding="10dp"     zhy:image="@drawable/im"     zhy:imageScaleType="center"     zhy:TitleText="山水美景"     zhy:TitleColor="#ff0000"     zhy:TitleSize="12sp" /></LinearLayout>

  最后效果图:

  

  相对第一、三步,第二步相对更复杂一些,下面我就对第二步里面的具体内容进行一下解析:

//获取自定义设置的属性    TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyleAttr, 0);    int n = typedArray.getIndexCount();    for(int i=0; i<n; i++){      int att = typedArray.getIndex(i);      //分别取出自定义属性设置的值      switch (att) {        case R.styleable.CustomImageView_TitleText:          titleText = typedArray.getString(att);          break;        case R.styleable.CustomImageView_TitleColor:          titleColor = typedArray.getColor(att, Color.RED);              break;        case R.styleable.CustomImageView_TitleSize:          titleSize = typedArray.getDimensionPixelSize(att, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,               16, getResources().getDisplayMetrics()));           break;        case R.styleable.CustomImageView_image:          image = BitmapFactory.decodeResource(getResources(), typedArray.getResourceId(att, 0));          break;        case R.styleable.CustomImageView_imageScaleType:          imageFillXY = typedArray.getInt(att, 0);          break;      }    }    typedArray.recycle();

  作用是获取我们在attrs中设置的自定义参数,在布局文件中进行的赋值。

  onMeasure()方法用于设置控件的宽度,控件的长宽值如何取得呢?下面我们就来进行一下解析:

  

  最后是我们绘图方法onDraw(Canvas canvas):

@Override  protected void onDraw(Canvas canvas) {    /**     * 空心矩形绘制     */     mPaint.setStrokeWidth(4);//设置空心线宽     mPaint.setStyle(Paint.Style.STROKE);//设置画笔为空心     mPaint.setColor(Color.CYAN);//设置画笔颜色     canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);      imageRect.left = getPaddingLeft();//获取图片左上角坐标     imageRect.right = mWidth - getPaddingRight();//获取图片右上角坐标     imageRect.top = getPaddingTop();//获取图片距控件顶部距离     imageRect.bottom = mHeight - getPaddingBottom();//确定图片底部坐标      mPaint.setColor(titleColor);//设置文本的颜色     mPaint.setStyle(Style.FILL);//设置文本内容的填充方式     /**     * 当前设置的宽度小于字体需要的宽度,将字体改为xxx...     */     if (titleRect.width() > mWidth) {       TextPaint paint = new TextPaint(mPaint);       String msg = TextUtils.ellipsize(titleText, 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(titleText, mWidth / 2 - titleRect.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);    }      //取消使用掉的块     imageRect.bottom -= titleRect.height();//因为文字内容占用一定的高度,所以图片的底部坐标需要上移。      if (imageFillXY == 0) {      canvas.drawBitmap(image, null, imageRect, mPaint);     } else {       //计算居中的矩形范围       imageRect.left = mWidth / 2 - image.getWidth() / 2;       imageRect.right = mWidth / 2 + image.getWidth() / 2;       imageRect.top = (mHeight - titleRect.height()) / 2 - image.getHeight() / 2;       imageRect.bottom = (mHeight - titleRect.height()) / 2 + image.getHeight() / 2;        canvas.drawBitmap(image, null, imageRect, mPaint);     }   }

  好了,到这里关于自定义View的初步学习就介绍完毕,如果你有更好的关于自定义View的文章,欢迎留言交流。