一个用来设置警示View 的呼吸式背景颜色的工具类BreathingViewHelper

一个简单的小工具类，用来设置警示 View 的呼吸式背景颜色

import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Build;
import android.view.View;

import java.util.Date;

/**
 * 一个简单的小工具类，用来设置警示 View 的呼吸式背景颜色
 * 
 * https://github.com/drakeet/BreathingViewHelper
 *
 * Created by drakeet on 6/12/15.
 */
public class BreathingViewHelper {

    private static AsyncTask<Void, Integer, Void> mAsyncTask;
    private static int mColor;
    private static boolean mCancelled;


    public static void setBreathingBackgroundColor(final View view, final int color) {
        Date firstDate = new Date();
        final long firstTime = firstDate.getTime();
        mAsyncTask = new AsyncTask<Void, Integer, Void>() {
            int n = 1, t = 3000;
            boolean increaseN;


            @Override protected Void doInBackground(Void... params) {
                while (!isCancelled() || !mCancelled) {
                    Date currentDate = new Date();
                    long diffTime = currentDate.getTime() - firstTime;
                    if (diffTime > n * t) {
                        increaseN = true;
                    }
                    if (increaseN) {
                        n++;
                        increaseN = false;
                    }
                    double y = getBreathingY(diffTime, n, t);
                    int alpha = (int) ((y * 0.618f + 0.382f) * 255);
                    int resultColor = setAlphaComponent(color, alpha);
                    mColor = resultColor;
                    publishProgress(resultColor);
                    try {
                        Thread.sleep(38);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                return null;
            }


            @Override protected void onProgressUpdate(Integer... values) {
                super.onProgressUpdate(values);
                view.setBackgroundColor(values[0]);
            }
        };
        executeAsyncTask(mAsyncTask);
    }


    public static void stopBreathingBackgroundColor(View view) {
        if (mAsyncTask != null) { BreathingViewHelper.mAsyncTask.cancel(true); }
        else { mCancelled = true; }
        smoothToOrigin(view);
    }


    @SafeVarargs private static <Params, Progress, Result> void executeAsyncTask(
            AsyncTask<Params, Progress, Result> task, Params... params) {
        if (Build.VERSION.SDK_INT >= 11) {
            task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, params);
        }
        else {
            task.execute(params);
        }
    }


    private static double getBreathingY(long time, int n, int t) {
        float k = 1.0f / 3;
        float pi = 3.1415f;
        float x = time / 1000.0f;
        t = (int) (t / 1000.0f);
        if (x >= ((n - 1) * t) && x < ((n - (1 - k)) * t)) {
            double i = pi / (k * t) * ((x - (0.5f * k * t)) - (n - 1) * t);
            return 0.5f * Math.sin(i) + 0.5f;
        }
        else if (x >= ((n - (1 - k)) * t) && x < n * t) {
            double j = pi / ((1 - k) * t) * ((x - (0.5f * (3 - k) * t)) - (n - 1) * t);
            double one = 0.5f * Math.sin(j) + 0.5f;
            return one * one;
        }
        return 0;
    }


    private static double getSinY(long time) {
        return 0.5f * Math.sin(3 * time / 1000.0f) + 0.5;
    }


    private static void smoothToOrigin(final View view) {
        Date firstDate = new Date();
        final long firstTime = firstDate.getTime();
        executeAsyncTask(new AsyncTask<Void, Integer, Void>() {
                    int n = 1, t = 4000;
                    boolean increaseN;


                    @Override protected Void doInBackground(Void... params) {
                        while (!isCancelled()) {
                            Date currentDate = new Date();
                            long diffTime = currentDate.getTime() - firstTime;

                            double y = getCosY(diffTime);
                            int alpha = (int) (y * 255);
                            int resultColor = setAlphaComponent(mColor, alpha);
                            if (alpha < 0.038 * 255) {
                                publishProgress(0);
                                this.cancel(true);
                                return null;
                            }
                            publishProgress(resultColor, alpha);
                            try {
                                Thread.sleep(38);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        return null;
                    }


                    @Override protected void onProgressUpdate(Integer... values) {
                        super.onProgressUpdate(values);
                        view.setBackgroundColor(values[0]);
                    }
                });
    }


    public static void smoothToTransparentFromColor(final View view, final int color) {
        Date firstDate = new Date();
        final long firstTime = firstDate.getTime();
        executeAsyncTask(new AsyncTask<Void, Integer, Void>() {
                    int n = 1, t = 4000;
                    boolean increaseN;


                    @Override protected Void doInBackground(Void... params) {
                        while (!isCancelled()) {
                            Date currentDate = new Date();
                            long diffTime = currentDate.getTime() - firstTime;

                            double y = getCosY(diffTime);
                            int alpha = (int) (y * Color.alpha(color));
                            int resultColor = setAlphaComponent(color, alpha);
                            if (alpha < 0.038 * 255) {
                                publishProgress(0);
                                this.cancel(true);
                                return null;
                            }
                            publishProgress(resultColor, alpha);
                            try {
                                Thread.sleep(38);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        return null;
                    }


                    @Override protected void onProgressUpdate(Integer... values) {
                        super.onProgressUpdate(values);
                        view.setBackgroundColor(values[0]);
                    }
                });
    }


    private static double getCosY(long diffTime) {
        return 0.5f * Math.cos(3 * diffTime / 1000.0f) + 0.5;
    }


    public static int setAlphaComponent(int color, int alpha) {
        if (alpha < 0 || alpha > 255) {
            throw new IllegalArgumentException("alpha must be between 0 and 255.");
        }
        return (color & 0x00ffffff) | (alpha << 24);
    }
}

用法：

//一个简单的小工具类，用来设置警示 View 的呼吸式背景颜色
View nav_header = findViewById(R.id.nav_header);
BreathingViewHelper.setBreathingBackgroundColor(nav_header, Color.parseColor("#f36c60"));
		nav_header.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				BreathingViewHelper.stopBreathingBackgroundColor(v);
			}
		});

Android从顶部显示一个Snackbar：TSnackBar
http://www.open-open.com/lib/view/open1446621175092.html