Android：启动画面没有显示，为什么？

Question

我正在学习 Android。从我到目前为止阅读的文档中，我无法弄清楚如何让启动视图显示（在睡眠期间屏幕保持空白）。看来我需要为主布局启动一个新活动，但这似乎很浪费（飞溅应该永远消失，我想重用它的线程）。

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class Ext3 extends Activity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.splash);

        Log.v("Ext3", "starting to sleep");

        try {
            Thread.sleep (5000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        Log.v("Ext3", "done sleeping");

        setContentView (R.layout.main);
    }

}

Answer 1

我相信你的启动画面永远不会显示，因为你从来没有给 UI 线程（你所在的）一个机会来绘制它，因为你只是睡在那里什么都不做。

我建议您不要使用 Thread.sleep，而是查看 Timer 或类似的东西来安排刷新和更改视图的内容；另一种方法是启动一个AsyncTask，您可以在其中睡觉，然后像现在一样更改视图。

不要休眠或以任何其他方式阻塞 UI 线程，这很糟糕......（导致 ANR）

Answer 2

当你像这样调用sleep 时，你正在阻塞 UI 线程。相反，将第二次调用setContentView 放在Runnable 中，创建一个Handler，并使用Handler 的postDelayed 方法运行Runnable。像这样的：

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.splash);
    Runnable endSplash = new Runnable() {
        @Override
        public void run() {
            setContentView (R.layout.main);
        }
    }
    new Handler().postDelayed(endSplash, 5000L);
}

Answer 3

我已经在我的应用程序中尝试过这段代码，它运行良好。也许它会对你有所帮助。

public class SplashScreen extends Activity {

    /**
     * The thread to process splash screen events
     */
    private Thread mSplashThread;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Splash screen view
        setContentView(R.layout.splash);



        final SplashScreen sPlashScreen = this;

        // The thread to wait for splash screen events
        mSplashThread = new Thread() {
            @Override
            public void run() {
                try {
                    synchronized (this) {
                        // Wait given period of time or exit on touch
                        wait(5000);
                    }
                } catch (InterruptedException ex) {
                }

                finish();

                // Run next activity
                Intent intent = new Intent();
                intent.setClass(sPlashScreen, MainActivity.class);
                startActivity(intent);
                stop();
            }
        };

        mSplashThread.start();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        return false;
    }

    /**
     * Processes splash screen touch events
     */
    @Override
    public boolean onTouchEvent(MotionEvent evt) {
        if (evt.getAction() == MotionEvent.ACTION_DOWN) {
            synchronized (mSplashThread) {
                mSplashThread.notifyAll();
            }
        }
        return true;
    }

}

Answer 4

这是基本启动画面的 sn-p

public class Splash extends Activity {

//private ProgressDialog pd = null;
private final int SPLASH_DISPLAY_LENGTH = 3000; 

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.splashscreen);
    //this.pd = ProgressDialog.show(this, "Initializing..", "Initializing Infraline...", true, false);

    /* New Handler to start the InfralineTabWidget-Activity
     * and close this Splash-Screen after some seconds.*/

    new Handler().postDelayed(new Runnable(){
        @Override
        public void run() {
        /* Create an Intent that will start the InfralineTabWidget-Activity. */
            Intent mainIntent = new Intent(Splash.this,InfralineTabWidget.class);
            Splash.this.startActivity(mainIntent);
            Splash.this.finish();
        }
    }, SPLASH_DISPLAY_LENGTH);

}

}

然后在你的 AndroidManifest.xml 中放

    <activity android:name=".Splash" android:theme="@android:style/Theme.NoTitleBar" android:configChanges="orientation|keyboardHidden">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

希望这对你有用:)