重写android返回键

在Activity里面加入下面代码：

@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
			showDialog(APP_EXIT);
			return true;
		} else
			return super.onKeyDown(keyCode, event);
	}

	@Override
	protected Dialog onCreateDialog(int id) {
		if (id == APP_EXIT) {
			return new AlertDialog.Builder(BaseActivity.this)
					.setMessage("是否退出程序?")
					.setTitle("用户退出")
					.setPositiveButton("确定",
							new DialogInterface.OnClickListener() {

								public void onClick(DialogInterface dialog,
										int which) {
									dialog.dismiss();
									android.os.Process
											.killProcess(android.os.Process
													.myPid());
									finish();

								}
							})
					.setNegativeButton("取消",
							new DialogInterface.OnClickListener() {

								public void onClick(DialogInterface dialog,
										int which) {
									dialog.dismiss();

								}
							}).create();

		}
		return null;

	}