Start activity only once

问题:

I want my app to start a activity only the first time the app launches. Any one got any idea?

I found this but it only shows a black screen.

public class WhatsNew extends Activity {    
    public static final String PREFS_NAME = "MyPrefsFile";
    protected void onCreate(Bundle state){    
        super.onCreate(state);
        SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
        boolean dialogShown = settings.getBoolean("dialogShown", false);
            if (!dialogShown) {
                // AlertDialog code here
                SharedPreferences.Editor editor = settings.edit();
                editor.putBoolean("dialogShown", true);
                editor.commit();    
            }
        }
    }

回答1:

When the app launches, set a flag in the activity preferences that the activity has already run. Default your setting to false, and then only start that activity if the flag isn't set. Note that if the user cleans your application data, or uninstalls it and later installs it again the activity would show again.

回答2:

I think that you talk about activities like "log" page that you would launch only once in your application's whole life. For this, you can use sharedPreferences:

SharedPreferences prefs;
SharedPreferences.Editor editor;

and below your startActivity(intent), you add:

prefs = getSharedPreferences("nbRepet",Context.MODE_PRIVATE);
editor = prefs.edit();
editor.putInt("nbRepet", 1);
editor.commit();

Now your variable nbRepet have 1 as value.

After that, you can add these lines ABOVE your startActivity(intent) to verify that your activity was never launched before:

//here you recover nbRepet's value..

preferences = MainActivity.this.getSharedPreferences("nbRepet", MODE_PRIVATE);      
int value = preferences.getInt("nbRepet", 0);

//.. and you verify if your activity is launched before.

if(value<1)
{
    startActivity(intent);
}

回答3:

You will need an Activity which checks a persisted boolean. ie,

onCreate(Bundle bundle)
{
    boolean firstRun = // persistance method here
    Intent toForward;
    if(firstRun)
        // Create an intent to start you "only once" activity
        // persist "firstRun" as false;
    else
        // Create an intent for your usual startup
    startActivity(toForward);
    finish();
}

回答4:

this will do the job for you

package com.example.startup;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
    //setContentView(R.layout.activity_main); //we don't need this line
    SharedPreferences settings=getSharedPreferences("prefs",0);
    boolean firstRun=settings.getBoolean("firstRun",false);
    if(firstRun==false)//if running for first time
      {
        SharedPreferences.Editor editor=settings.edit();
        editor.putBoolean("firstRun",true);
        editor.commit();
        Intent i=new Intent(MainActivity.this,Second.class);//Activity to be     launched For the First time 
        startActivity(i);
        finish();
    }
    else
    {
        Intent a=new Intent(MainActivity.this,Main.class);//Default Activity 
        startActivity(a);
        finish();
    }
   }

}

回答5:

Depends on what "first time" means. Easiest way is to put some flag into the SharedPreferences... but that can stay around for a while. ^^

回答6:

If you mean that onCreate should be invoked only once when "start only once when app is launched", you could set the launchMode of the acitivty to singleInstance or singleTask in the manifest.

回答7:

See my answer in this post, regarding this same issue.

I recommend checking the SharedPreference value for whether the app has previously been ran, inside of the onResume().