App的小功能点，很简单几十行代码就可以实现

主页面代码

package com.buildingbuilding;import android.content.Intent;import android.os.Handler;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.WindowManager;import android.widget.TextView;import com.buildingbuilding.activitys.BuildingActivity;public class MainActivity extends AppCompatActivity { private TextView textView; private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what != 0) { textView.setText(msg.what + "秒后进入APP"); } else { Intent intent = new Intent(MainActivity.this, BuildingActivity.class); startActivity(intent); finish(); } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); init(); } private void init() { //全屏显示 getSupportActionBar().hide(); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); textView = (TextView) findViewById(R.id.textView); textView.setText("布丁布丁"); new CountDown().start(); } //进入APP倒计时 class CountDown extends Thread { int count = 3; @Override public void run() { try { while (count >= 0) { sleep(1000); Message message = new Message(); message.what = count; handler.sendMessage(message); count--; } } catch (InterruptedException e) { e.printStackTrace(); } } }}

基本思路就是，通过一个计时线程来控制主线程（即UI线程）来更新UI

通过Handler来接受来自计时线程的Message

private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what != 0) { textView.setText(msg.what + "秒后进入APP"); } else { Intent intent = new Intent(MainActivity.this, BuildingActivity.class); startActivity(intent); finish(); } } };

2.计时线程（内部类），设置每隔1秒睡一次，共3秒

//进入APP倒计时 class CountDown extends Thread { int count = 3; @Override public void run() { try { while (count >= 0) { sleep(1000); Message message = new Message(); message.what = count; handler.sendMessage(message); count--; } } catch (InterruptedException e) { e.printStackTrace(); } } }

3.最后别忘了在init（）方法中启动线程

private void init() { //全屏显示 getSupportActionBar().hide(); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); textView = (TextView) findViewById(R.id.textView); textView.setText("布丁布丁"); new CountDown().start(); }

OK，现在基本都完成了，来看效果

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