Activityのスタックの操作

package com.meishe.sdkdemo.utils;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

import java.util.Stack;

import static android.app.Activity.RESULT_OK;

/**
 * Created by Newnet on 2017/1/9.
 */

public class AppManager {

    private static Stack activityStack = new Stack<>();
    private volatile static AppManager instance = new AppManager();

    private AppManager() {
    }

    /**
     *  
     */
    public static AppManager getInstance() {
        if (instance == null) {
            instance = new AppManager();
        }
        return instance;
    }

    /**
     *  Activity 
     */
    public void addActivity(Activity activity) {
        if (activityStack == null) {
            activityStack = new Stack();
        }
        activityStack.add(activity);
    }

    public void popActivity() {
        if (activityStack.size() > 0) {
            activityStack.pop();
        }
    }

    /**
     *  Activity（ ）
     */
    public Activity currentActivity() {
        if (activityStack.size() > 0) {
            Activity activity = activityStack.lastElement();
            return activity;
        } else {
            return null;
        }
    }

    /**
     *  Activity
     */
    public void finishAllActivity() {
        for (int i = 0, size = activityStack.size(); i < size; i++) {
            if (null != activityStack.get(i)) {
                activityStack.get(i).finish();
            }
        }
        activityStack.clear();
    }

    public int activietySizes() {
        if (null != activityStack) {
            return activityStack.size();
        }
        return 0;
    }


    /**
     *  
     *
     * @param activity
     * @param cls
     * @param bundle
     */
    public void jumpActivity(Activity activity, Class extends Activity> cls, Bundle bundle) {
        Intent intent = new Intent(activity, cls);
        if (bundle != null) {
            intent.putExtras(bundle);
        }
        activity.startActivity(intent);
    }

    /**
     *  
     *
     * @param activity
     * @param cls
     * @param bundle
     * @param requstcode
     */
    public void jumpActivityForResult(Activity activity, Class extends Activity> cls, Bundle bundle, int requstcode) {
        Intent intent = new Intent(activity, cls);
        if (bundle != null) {
            intent.putExtras(bundle);
        }
        activity.startActivityForResult(intent, requstcode);
    }


    /**
     *  stack 
     */
    public int getActivitySize() {
        if (null != activityStack) {
            return activityStack.size();
        }
        return 0;
    }


    /**
     *  
     */
    private long exitTime = 0;

    @SuppressWarnings("deprecation")
    public void safetyExitApp(Context context) {
        if ((System.currentTimeMillis() - exitTime) > 2000) {
            Toast.makeText(context.getApplicationContext(), " ",
                    Toast.LENGTH_SHORT).show();
            exitTime = System.currentTimeMillis();
        } else {
            try {
                finishAllActivity();
                //  
                android.os.Process.killProcess(android.os.Process.myPid());
                System.exit(0);
            } catch (Exception e) {
            }
        }
    }
}