APP实用开发——SplashScreen页面倒计时跳转

Handler对象的postDelayed方法

闪屏，就是SplashScreen，也可以说是启动画面，就是启动的时候，闪(展示)一下，持续数秒后，自动关闭。
android的实现非常简单，使用Handler对象的postDelayed方法就可以实现。在这个方法里传递一个Runnable对象和一个延迟的时间。该方法实现了一个延迟执行的效果，延迟的时间由第2个参数指定，单位是毫秒。第一个参数是Runnable对象，里面包含了延迟后需要执行的操作。demo代码如下：

public class JumpActivity extends Activity {
    TextView textView;
    int time=3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.jump);
        textView= (TextView) findViewById(R.id.textview);

        handler.postDelayed(runnable,3000);

    }
    Handler handler=new Handler();
    Runnable runnable=new Runnable() {
        @Override
        public void run() {
            time--;
            handler.postDelayed(this,2000);
            textView.setText("跳转："+time+"秒");

            if(time==0){
                Intent intent=new Intent(JumpActivity.this,TestActivity.class);
                startActivity(intent);
                finish();
            }else {
                textView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent=new Intent(JumpActivity.this,TestActivity.class);
                        startActivity(intent);
                        //结束线程
                        handler.removeCallbacks(runnable);
                        finish();
                    }
                });
            }
        }
    };
}

CountDownTimer类

以前编程的时候，遇到倒计时的功能时，经常自己去写，但其实Android已经帮封装好了一个倒计时类CountDownTimer，其实是将后台线程的创建和Handler队列封装成为了一个方便的类调用。
闪屏页用到了handler和CountDownTimer类，还需配置一下Activity的主题，这里是：android:theme=”@android:style/Theme.NoTitleBar.Fullscreen” 全屏主题的意思。

public class Welcome extends Activity {  
    private static final String MY_DB_FirstCheck = "my_db";  
    private TextView tv;  

    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);  
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,  
                WindowManager.LayoutParams.FLAG_FULLSCREEN);  
        setContentView(R.layout.welcome_layout);  
        tv= (TextView) findViewById(R.id.TView_countdown);  

        final SharedPreferences sharedpreferences = getSharedPreferences(  
                MY_DB_FirstCheck, Context.MODE_PRIVATE);  


        final boolean hasVisited = sharedpreferences.getBoolean("hasVisited",  
                false);  

        countdowntimer = new MyCountdownTimer(3000, 1000);  
        countdowntimer.start();  

        handler.postDelayed(new Runnable() {  

            @Override  
            public void run() {  
                if (!hasVisited) {  

                    Intent intent = new Intent();  
                    intent.setClass(Welcome.this, Login.class);  
                    startActivity(intent);  


                    Editor edit = sharedpreferences.edit();  
                    edit.putBoolean("hasVisited", true);  
                    edit.commit();  
                } else {  
                    Intent intent = new Intent();  
                    intent.setClass(Welcome.this, MainActivity.class);  
                    startActivity(intent);  
                }  
                finish();  
            }  
        }, 3000);  
    }  

    private Handler handler = new Handler();  
    private MyCountdownTimer countdowntimer;  


/** 
* 继承 CountDownTimer 防范 
* 参数：  倒计时总数，单位为毫秒、每隔多久调用onTick一次 
* 重写 父类的方法 onTick() 、 onFinish() 
*/
    protected class MyCountdownTimer extends CountDownTimer {  

        public MyCountdownTimer(long millisInFuture, long countDownInterval) {  
            super(millisInFuture, countDownInterval);  
        }  

        @Override  
        public void onTick(long millisUntilFinished) {  
           tv.setText("倒计时(" + millisUntilFinished / 1000 + ")");  
        }  

        @Override  
        public void onFinish() {  
            tv.setText("正在跳转"); 
        }  

    }  
}  

sendEmptyMessageDelayed

public class WelcomeActivity extends Activity {

    // 声明控件对象
    private TextView textView;
    private int count = 5;
    private Animation animation;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 去除标题
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_welcome);
        // 初始化控件对象
        textView = (TextView) findViewById(R.id.textView);
        animation = AnimationUtils.loadAnimation(this, R.anim.animation_text);
        //textView.startAnimation(animation);
        handler.sendEmptyMessageDelayed(0, 1000);

    }

    private int getCount() {
        count--;
        if (count == 0) {
            Intent intent = new Intent(this, MainActivity.class);
            startActivity(intent);
            finish();
        }
        return count;
    }

    private Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            if (msg.what == 0) {
                textView.setText(getCount()+"");
                handler.sendEmptyMessageDelayed(0, 1000);
                animation.reset();
                textView.startAnimation(animation);
            }

        };

    };

}

activity_welcome.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/image"
    tools:context="${relativePackage}.${activityClass}" >

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:orientation="horizontal" >

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"
            android:text="广告倒计时："
            android:textColor="#ffffff"
            android:textSize="20sp" />

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"
            android:text="5"
            android:textColor="#ffffff"
            android:textSize="20sp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"
            android:text="秒"
            android:textColor="#ffffff"
            android:textSize="20sp" />
    </LinearLayout>

</FrameLayout>

动画的xml文件animation_text.xml存放在了res/anim目录下，实现透明度和缩放的动画。
animation_text.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" >

    <alpha
        android:duration="1000"
        android:fromAlpha="0.0"
        android:toAlpha="1.0" />

    <scale
        android:duration="800"
        android:fromXScale="1.5"
        android:fromYScale="1.5"
        android:pivotX="50%"
        android:pivotY="50%"
        android:toXScale="1.0"
        android:toYScale="1.0" />

</set>