Android自定义View训练【1】

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前言：最近这段时间想根据网上博客的案例，自己练习自定义View，代码仅仅作为练习用，还有很多不足之处，见谅

案例取自：http://blog.csdn.net/wingichoy/article/details/50455412

先上传源码

public class PracticeView1 extends View {    private float mrectwidth = 200;    private float mrectheight = 100;    private float mround = 20;    private float len = 15;    private Paint mPaint = new Paint();    private Path mPath = new Path();    public PracticeView1(Context context) {        super(context);    }    public PracticeView1(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int mwidthmode = MeasureSpec.getMode(widthMeasureSpec);        int mwidthsize = MeasureSpec.getSize(widthMeasureSpec);        int mheightmode = MeasureSpec.getMode(heightMeasureSpec);        int mheightsize = MeasureSpec.getSize(heightMeasureSpec);        mrectwidth = (float) mwidthsize;        mrectheight = (float) mheightsize;        if(mwidthmode == MeasureSpec.AT_MOST) {            mrectwidth = (float) (600/2);        }        if(mheightmode == MeasureSpec.AT_MOST) {            mrectheight = (float) (300/2);        }        setMeasuredDimension((int) mrectwidth, (int) mrectheight);        Log.d("SunJ:", "mrectwidth " + String.valueOf(mrectwidth) + ",  mrectheight " + String.valueOf(mrectheight));    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        mPaint.setColor(Color.GRAY);        mPaint.setStyle(Paint.Style.FILL);        mPaint.setAntiAlias(true);        RectF mRectF = new RectF(0, 0, mrectwidth, mrectheight-len);        canvas.drawRoundRect(mRectF, mround, mround, mPaint);        mPath.moveTo(mrectwidth/2, mrectheight);        mPath.lineTo(mrectwidth/2+len, mrectheight-len);        mPath.lineTo(mrectwidth/2-len, mrectheight-len);        mPath.close();        canvas.drawPath(mPath, mPaint);    }}

效果图：

要点：

1.重写onMeasure()是为了在xml中设置layout_weight/layout_height属性为wrap_content时，不会变成match_parent

2.在onDraw()里面的矩形尺寸是由onMeasure()来得到的，这样子，在xml中设置具体的宽和高时，该矩形的大小同样也会发生相应的变化，这样，才能做到随意改变大小；而不会出现当设置具体的宽和高时，view缺胳膊少腿或者是多出空白的区域

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