android 返回键退出两种表现方式

一： 点击一次返回键退出相关代码

protected void dialog() {
AlertDialog.Builder builder = new Builder(HomeActivity.this);
builder.setMessage("确定要退出吗?");
builder.setTitle("提示");
builder.setPositiveButton("确认",
new android.content.DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
//HomeActivity.this.finish();
AgentApplication.getInstance().onTerminate();
}
});
builder.setNegativeButton("取消",
new android.content.DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
builder.create().show();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
dialog();
return false;
}
return false;
}
二： 点击两次返回键自动退出

public boolean onKeyDown(int keyCode, KeyEvent event)
{
if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN)
{

if((System.currentTimeMillis()-exitTime) > 2000) //System.currentTimeMillis()无论何时调用，肯定大于2000
{
Toast.makeText(getApplicationContext(), "再按一次退出程序",Toast.LENGTH_SHORT).show();
exitTime = System.currentTimeMillis();
}
else
{
finish();
System.exit(0);
}

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