Android退出应用最优雅的方式(改进版)

import java.util.ArrayList;
import java.util.List;

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

public class BaseActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // 添加Activity到堆栈
    AtyContainer.getInstance().addActivity(this);
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    // 结束Activity&从栈中移除该Activity
    AtyContainer.getInstance().removeActivity(this);
  }

}

class AtyContainer {

  private AtyContainer() {
  }

  private static AtyContainer instance = new AtyContainer();
  private static List<Activity> activityStack = new ArrayList<Activity>();

  public static AtyContainer getInstance() {
    return instance;
  }

  public void addActivity(Activity aty) {
    activityStack.add(aty);
  }

  public void removeActivity(Activity aty) {
    activityStack.remove(aty);
  }

  /**
   * 结束所有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 class BaseActivity extends Activity {

  private static final String EXITACTION = "action.exit";

  private ExitReceiver exitReceiver = new ExitReceiver();

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    IntentFilter filter = new IntentFilter();
    filter.addAction(EXITACTION);
    registerReceiver(exitReceiver, filter);
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(exitReceiver);
  }

  class ExitReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
      BaseActivity.this.finish();
    }

  }

}

  android.os.Process.killProcess(android.os.Process.myPid());
  System.exit(0);

  ActivityManager manager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
  manager.killBackgroundProcesses(getPackageName());

 private static final String TAG_EXIT = "exit";

  @Override
  protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    if (intent != null) {
      boolean isExit = intent.getBooleanExtra(TAG_EXIT, false);
      if (isExit) {
        this.finish();
      }
    }
  }

Intent intent = new Intent(this,MainActivity.class);
    intent.putExtra(MainActivity.TAG_EXIT, true);
    startActivity(intent);

private boolean mIsExit;
@Override
  /**
   * 双击返回键退出
   */
  public boolean onKeyDown(int keyCode, KeyEvent event) {

    if (keyCode == KeyEvent.KEYCODE_BACK) {
      if (mIsExit) {
        this.finish();

      } else {
        Toast.makeText(this, "再按一次退出", Toast.LENGTH_SHORT).show();
        mIsExit = true;
        new Handler().postDelayed(new Runnable() {
          @Override
          public void run() {
            mIsExit = false;
          }
        }, 2000);
      }
      return true;
    }

    return super.onKeyDown(keyCode, event);
  }