自定义控件（1）---初探之不断闪烁的圆环

小案例的原理：

1、new Thread(mCustomView).start();

2、public class CustomView extends View implements Runnable

3、

<strong>	public void run() {
		/*确保线程不断执行不断刷新界面*/
		while (true) {
			try {
				/*如果半径小于200则自加否则大于200后重置半径值以实现往复*/
				if (radiu <= 200) {
					radiu += 10;

					//刷新View
					postInvalidate();
				} else {
					radiu = 0;
				}
				// 每执行一次暂停40毫秒
				Thread.sleep(40);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}</strong>

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF"
    android:orientation="vertical" >

    <com.aigestudio.customviewdemo.views.CustomView
        android:id="@+id/main_cv"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

MainActivity

package com.aigestudio.customviewdemo.activities;

import android.app.Activity;
import android.os.Bundle;

import com.aigestudio.customviewdemo.R;
import com.aigestudio.customviewdemo.views.CustomView;

/**
 * 主界面
 */
public class MainActivity extends Activity {
	private CustomView mCustomView;// 我们的自定义View

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		// 获取控件
		mCustomView = (CustomView) findViewById(R.id.main_cv);

		/*
		 * 开线程
		 */
		new Thread(mCustomView).start();
	}
}

MeasureUtil

package com.aigestudio.customviewdemo.views;

import android.app.Activity;
import android.util.DisplayMetrics;

/**
 * 测绘工具类
 */
public final class MeasureUtil {
	/**
	 * 获取屏幕尺寸
	 * 
	 * @param activity
	 *            Activity
	 * @return 屏幕尺寸像素值，下标为0的值为宽，下标为1的值为高
	 */
	public static int[] getScreenSize(Activity activity) {
		DisplayMetrics metrics = new DisplayMetrics();
		activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);
		return new int[] { metrics.widthPixels, metrics.heightPixels };
	}
}

package com.aigestudio.customviewdemo.views;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

/**
 * 自定义View
 */
public class CustomView extends View implements Runnable {
	private Paint mPaint;// 画笔
	private Context mContext;// 上下文环境引用

	private int radiu;// 圆环半径

	public CustomView(Context context) {
		this(context, null);
	}

	public CustomView(Context context, AttributeSet attrs) {
		super(context, attrs);
		mContext = context;

		// 初始化画笔
		initPaint();
	}

	/**
	 * 初始化画笔
	 */
	private void initPaint() {
		// 实例化画笔并打开抗锯齿
		mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

		/*
		 * 设置画笔样式为描边，圆环嘛……当然不能填充不然就么意思了
		 * 
		 * 画笔样式分三种：
		 * 1.Paint.Style.STROKE：描边
		 * 2.Paint.Style.FILL_AND_STROKE：描边并填充
		 * 3.Paint.Style.FILL：填充
		 */
		mPaint.setStyle(Paint.Style.STROKE);

		// 设置画笔颜色为浅灰色
		mPaint.setColor(Color.LTGRAY);

		/*
		 * 设置描边的粗细，单位：像素px
		 * 注意：当setStrokeWidth(0)的时候描边宽度并不为0而是只占一个像素
		 */
		mPaint.setStrokeWidth(10);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);

		// 绘制圆环
		canvas.drawCircle(MeasureUtil.getScreenSize((Activity) mContext)[0] / 2, MeasureUtil.getScreenSize((Activity) mContext)[1] / 2, radiu, mPaint);
	}

	@Override
	public void run() {
		/*
		 * 确保线程不断执行不断刷新界面
		 */
		while (true) {
			try {
				/*
				 * 如果半径小于200则自加否则大于200后重置半径值以实现往复
				 */
				if (radiu <= 200) {
					radiu += 10;

					// 刷新View
					postInvalidate();
				} else {
					radiu = 0;
				}

				// 每执行一次暂停40毫秒
				Thread.sleep(40);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}