android自定义View处理padding和wrap_content和自定义属性

android View 处理padding

@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int paddingLeft=getPaddingLeft();
        int paddingRight=getPaddingRight();
        int paddingTop=getPaddingTop();
        int paddingBottom=getPaddingBottom();
        int width = getWidth()-paddingLeft-paddingRight;
        int height = getHeight()-paddingTop-paddingBottom;
        canvas.drawRect(0+paddingLeft,0+paddingTop,width+paddingRight,height+paddingBottom,mPaint);
    }

对wrap_content属性进行处理

在onMeasure方法中指定一个默认的宽和高，在设置wrap_content属性时设置此默认的宽和高就可以了：
setMeasuredDimension() 方法px

@Override
protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec,heightMeasureSpec);
    int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
    int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
    if(widthSpecMode==MeasureSpec.AT_MOST&&heightSpecMode==MeasureSpec.AT_MOST){
        setMeasuredDimension(600,600);
    }else if(widthSpecMode==MeasureSpec.AT_MOST){
        setMeasuredDimension(600,heightSpecSize);
    }else if(heightSpecMode==MeasureSpec.AT_MOST){
        setMeasuredDimension(widthSpecSize,600);
    }
}

自定义属性

在values目录下创建attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="RectView">
        <attr name="rect_color" format="color"/>
    </declare-styleable>
</resources>

解析自定义属性的值

public RectView(Context context, AttributeSet attrs) {
    super(context, attrs);
    TypedArray mTypedArray=context.obtainStyledAttributes(attrs,R.styleable.RecyView);
    // 提取RectView属性集合的rect_color属性。如果没设置，默认值为Color.RED
    mColor=mTypedArray.getColor(R.styleable.RectView_rect_color,Color.RED);
    // 获取资源后要及时回收
    mTypedArray.recycle();
    initDraw();
}

<com.xx.RectView
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/rv_rect"
    android:layout_width="wrap_content"
    android:layout_height="200dp"
    android:layout_below="@id/iv_text"
    android:layout_marginTop="50dp"
    android:layout_centerHorizontal="true"
    android:padding="10dp"
    app:rect_color="@android:color/holo_blue_light"/>

完整代码：

public class RectView extends View {
    private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private int mColor=Color.RED;
    public RectView(Context context) {
        super(context);
        initDraw();
    }

    public RectView(Context context,AttributeSet attrs) {
        super(context, attrs);
        TypedArray mTypedArray=context.obtainStyledAttributes(attrs,R.styleable.RectView);
        //提取RectView属性集合的rect_color属性。如果没设置，默认值为Color.RED
        mColor=mTypedArray.getColor(R.styleable.RectView_rect_color,Color.RED);
        //获取资源后要及时回收
        mTypedArray.recycle();
        initDraw();
    }

    public RectView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initDraw();
    }

    private void initDraw() {
        mPaint.setColor(mColor);
        mPaint.setStrokeWidth((float)1.5);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec,heightMeasureSpec);
        int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
        int widthSpecSize=MeasureSpec.getSize(widthMeasureSpec);
        int heightSpecSize=MeasureSpec.getSize(heightMeasureSpec);
        if(widthSpecMode==MeasureSpec.AT_MOST&&heightSpecMode==MeasureSpec.AT_MOST){
            setMeasuredDimension(400,400);
        }else if(widthSpecMode==MeasureSpec.AT_MOST){
            setMeasuredDimension(400,heightSpecSize);
        }else if(heightSpecMode==MeasureSpec.AT_MOST){
            setMeasuredDimension(widthSpecSize,400);
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int paddingLeft = getPaddingLeft();
        int paddingRight = getPaddingRight();
        int paddingTop = getPaddingTop();
        int paddingBottom = getPaddingBottom();
        int width = getWidth()-paddingLeft-paddingRight;
        int height = getHeight()-paddingTop-paddingBottom;
        canvas.drawRect(0+paddingLeft,0+paddingTop,width+paddingRight,height+paddingBottom,mPaint);
    }
}