<activity
android:label="@string/app_name"
android:name=".WelcomeActivity" 
android:theme="@android:style/Theme.NoTitleBar">
<此种方法，设置全屏可以消除刚进入Activity时，看到的那个title>

<activity
android:label="@string/app_name"
android:name=".WelcomeActivity" 
android:theme="@android:style/Theme.NoTitleBar.FullScreen">

package com.example.hideproject;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.Window;
import android.view.WindowManager;
import android.support.v4.app.NavUtils;
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//隐藏标题栏
requestWindowFeature(Window.FEATURE_NO_TITLE);
//隐藏状态栏
//定义全屏参数
int flag=WindowManager.LayoutParams.FLAG_FULLSCREEN;
//获得当前窗体对象
Window window=MainActivity.this.getWindow();
//设置当前窗体为全屏显示
window.setFlags(flag, flag);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}