帮助 Android 应用程序加载页面中的事件顺序

Question

I'm learning Android (ironically from a cross of the developer site from Google and SO), and I'm having trouble with an early step. The order of events I am going for is: 1. Load splash page 2. After 5 seconds (this is temporary... will eventually be actually used to cover up load time), switch to main view 3. On the main view load, pop a nag window (currently an alertDialog), which gives the user two button press options

I have this all working except for ONE problem. The nag window pops immediately when the splash page comes up (when the app starts). You can see the splash page is working fine beneath the nag window, it waits 5 seconds, then switches to main. Can someone please tell me what I'm doing wrong as far as trying to get the nag window to NOT pop until the splash page count is done? Main java page is pasted below:

public class MyProject extends Activity {

    protected Dialog mSplashDialog;
    private static final int NAG_BOX = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        MyStateSaver data = (MyStateSaver) getLastNonConfigurationInstance();
        if (data != null) {
            // Show splash screen if still loading
            if (data.showSplashScreen) {
                showSplashScreen();
            }
            setContentView(R.layout.main);    
            showDialog(NAG_BOX);

            // Rebuild your UI with your saved state here
        } else {
            showSplashScreen();
            setContentView(R.layout.main);
            // Do your heavy loading here

        }
    }

    @Override
    public Object onRetainNonConfigurationInstance() {
        MyStateSaver data = new MyStateSaver();
        // Save your important data here

        if (mSplashDialog != null) {
            data.showSplashScreen = true;
            removeSplashScreen();
        }
        return data;
    }

    /**
     * Removes the Dialog that displays the splash screen
     */
    protected void removeSplashScreen() {
        if (mSplashDialog != null) {
            mSplashDialog.dismiss();
            mSplashDialog = null;
        }
    }

    /**
     * Shows the splash screen over the full Activity
     */
    protected void showSplashScreen() {
        mSplashDialog = new Dialog(this, R.style.SplashScreen);
        mSplashDialog.setContentView(R.layout.splash);
        mSplashDialog.setCancelable(false);
        mSplashDialog.show();

        // Set Runnable to remove splash screen just in case
        final Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
          @Override
          public void run() {
            removeSplashScreen();
          }
        }, 5000);
    }

    /**
     * Simple class for storing important data across config changes
     */
    private class MyStateSaver {
        public boolean showSplashScreen = false;
        // Your other important fields here
    }

     @Override
        protected Dialog onCreateDialog(int id) {
            switch (id) {

            case NAG_BOX:
                // This example shows how to add a custom layout to an AlertDialog
                LayoutInflater factory = LayoutInflater.from(this);
                final View textEntryView = factory.inflate(R.layout.nagbox, null);
                return new AlertDialog.Builder(MyProject.this)
                    .setView(textEntryView)
                    .setNegativeButton("Maybe Later", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int whichButton) {
                           dismissDialog(NAG_BOX);
                        }
                    })
                    .setPositiveButton("Go To Site", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int whichButton) {

                            Uri url = Uri.parse("http://www.google.com");
                            Intent intent = new Intent(Intent.ACTION_VIEW, url);
                            startActivity(intent);
                        }
                    })

                    .create();
            }
            return null;
        }
}

Answer 1

if (data != null) {
    // Show splash screen if still loading
    if (data.showSplashScreen) {
        showSplashScreen();
    }
    setContentView(R.layout.main);    
    showDialog(NAG_BOX);

In this portion of your code your nested if, although shows your splashscreen, does not mean it will not show the NAG_BOX

You need a condition around the showDialog(NAG_BOX) which is called after the showSplashSreen() function

Answer 2

Why not invoke showDialog(NAG_BOX) after you dismiss your splash screen?

protected void removeSplashScreen() {
    if (mSplashDialog != null) {
        mSplashDialog.dismiss();
        mSplashDialog = null;
        showDialog(NAG_BOX);
    }
}

Answer 3

The preferred method is to use AsyncTask for long operations. You can use the publishProgress() method to update the splash screen to indicate progress. This will also create a nice stub spot for your fake wait time.

Then in AsyncTask's onPostExecute() you can show your dialog.

http://developer.android.com/reference/android/os/AsyncTask.html