Android开发中拦截或屏蔽返回键

在Android开发中我们常常会遇到需要拦截或屏蔽返回键的 需求，对拦截后的返回键进行特殊操作

这里写代码片public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if ((System.currentTimeMillis() - mExitTime) > 2000) {// System.currentTimeMillis()无论何时调用，肯定大于2000
                Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
                mExitTime = System.currentTimeMillis();
            }
            return true;
        } else if (keyCode == KeyEvent.KEYCODE_MENU) {
            System.out.println("您按了菜单键");
            CreatAlertDialog("您按了菜单键");
            Toast.makeText(this, "您按了菜单键", Toast.LENGTH_SHORT).show();
            return true;
        } else if (keyCode == KeyEvent.KEYCODE_HOME) {
            // 由于Home键为系统键，此处不能捕获，需要重写onAttachedToWindow()
            System.out.println("您按了HOME键");
            CreatAlertDialog("您按了HOME键");
            Toast.makeText(this, "您按了HOME键", Toast.LENGTH_SHORT).show();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

    private void CreatAlertDialog(String str){
        new AlertDialog.Builder(this).setIcon(R.drawable.ic_launcher)
        .setMessage(str)
        .show();
    }

 返回true时则禁掉返回键；

2， dialog对话框拦截返回键

Dialog dialog = new Dialog(this, R.style.loginDialogTheme);
 dialog.setOnKeyListener(new DialogInterface.OnKeyListener() {
         @Override
              public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
                                if (keyCode == KeyEvent.KEYCODE_BACK){//监听返回键
                                    System.exit(0);
                                }
                                return false;//返回键可用，点击返回键退出应用
                            }
                        });

3,frgment 消耗返回事件

 @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {

            if (mHomeTabIndexEnum != null) {
                // 将返回键分给fragment处理
                Fragment currentFragment = mFragmentManager
                        .findFragmentByTag(mHomeTabIndexEnum.toString());
                if (mHomeTabIndexEnum == HomeTabIndexEnum.TAB_HOME_LIVE_CHINA) {
                    LiveChinaFragment liveChinaFragment = (LiveChinaFragment) currentFragment;
                    // 消费了返回事件
                    boolean onkeyDownBack = liveChinaFragment.onkeyDownBack();
                    if (onkeyDownBack) {
                        return true;
                    }
                } else if (mHomeTabIndexEnum == HomeTabIndexEnum.TAB_HOME_PANDA_LIVE) {
                    LovePandaFragment lovePandaFragment = (LovePandaFragment) currentFragment;
                    // 消费了返回事件
                    boolean onkeyDownBack = lovePandaFragment.onkeyDownBack();
                    if (onkeyDownBack) {
                        return true;
                    }
                }
            }
            long now = new Date().getTime();
            if (now - mLastBackTime < 2000) {

                // getSharedPreferences("config",
                // MODE_PRIVATE).edit().clear().commit;
                return super.onKeyDown(keyCode, event);
            } else {
                mLastBackTime = now;
                Toast.makeText(MainActivity.this, "连续点击两次退出应用!!!",
                        Toast.LENGTH_SHORT).show();

            }
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }