Convenient Super-Class for custom view.

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自定义View对于新手来说是道坎儿。基本来说有三种自定义View：

  • 继承自View，覆写onDraw方法，绘制需要的内容。
  • 继承自View的子类，如Button、RadioButton等，扩展其功能。
  • 继承自ViewGroup或XxxLayout，inflate布局，在自定义ViewGroup中控制子View。
    对于继承自View的方式，一般需要关心onMeasure，onDraw，onSizeChanged。而onMeasure基本有一套通用的处理方式，下面就来引入一个文件，一方面提供了这个通用模板，另一方面也可以直接使用作为自定义View的基类。

    更多关于SavedState的信息，转到另一篇博客查看。

RayView

也可以直接下载

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package com.kyleduo.view;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;

/**
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *
 * Convenient class for custom views, providing easy way to control 
 * width and height for custom views.
 * 
 * Sub-Classes override getMinimumMeasureWidth and getMinimumMeasureHeight
 * to provide minimum width and height excluding paddings, the sizes will 
 * be used for calculate real size for measure.
 * 
 * mWidth and mHeight are protected properties for sub-Classes. If
 * you want to maintain some other values related to the size. You can 
 * override onSizeRealChanged() method to deal with thees staff. This 
 * method is invoked only the size was REALLY changed in onSizeChanged().
 * 
 * @author kyle
 * 
 * Created by kyle on 15/11/21.
 */
public class RayView extends View {
	protected int mWidth, mHeight;

	public RayView(Context context) {
		super(context);
		init(null);
	}

	public RayView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init(attrs);
	}

	public RayView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		init(attrs);
	}

	protected void init(AttributeSet attrs) {

	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		if (customOnMeasure()) {
			setMeasuredDimension(measure(widthMeasureSpec, true), measure(heightMeasureSpec, false));
		} else {
			super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		}
	}

	protected int measure(int measureSpec, boolean WOH) {
		int size = MeasureSpec.getSize(measureSpec);
		int mode = MeasureSpec.getMode(measureSpec);
		int measured;

		int measureMinimum = WOH ? getMinimumMeasureWidth() : getMinimumMeasureHeight();

		measureMinimum = Math.max(measureMinimum, measureMinimum + getPaddingLeft() + getPaddingRight());
		measureMinimum = Math.max(measureMinimum, getSuggestedMinimumWidth());

		if (mode == MeasureSpec.EXACTLY) {
			measured = Math.max(measureMinimum, size);
		} else {
			measured = measureMinimum;
			if (mode == MeasureSpec.AT_MOST) {
				measured = Math.min(measured, size);
			}
		}

		return measured;
	}

	protected int getMinimumMeasureWidth() {
		return getSuggestedMinimumWidth();
	}

	protected int getMinimumMeasureHeight() {
		return getSuggestedMinimumHeight();
	}

	protected boolean customOnMeasure() {
		return true;
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		super.onSizeChanged(w, h, oldw, oldh);
		if (w != oldw || h != oldh) {
			mWidth = w;
			mHeight = h;
			onSizeRealChanged(w, h);
		}
	}

	protected void onSizeRealChanged(int w, int h) {

	}
}