How to prevent the activity from loading twice on

问题:

I am trying to prevent the activity from loading twice if I press the button twice instantly after the first click.

I have an activity which loads on click of a button, say

 myButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View view) {
       //Load another activity
    }
});

Now because the activity to be loaded has network calls, it takes a little time to load (MVC). I do show a loading view for this but if I press the button twice before that, I can see the activity being loaded twice.

Do any one know how to prevent this?

回答1:

In the button's event listener, disable the button and show another activity.

    Button b = (Button) view;
    b.setEnabled(false);

    Intent i = new Intent(this, AnotherActitivty.class);
    startActivity(i);

Override onResume() to re-enable the button.

@Override
    protected void onResume() {
        super.onResume();

        Button button1 = (Button) findViewById(R.id.button1);
        button1.setEnabled(true);
    }

回答2:

Add this to your Activity definition in Androidmanifest.xml...

android:launchMode = "singleInstance"

回答3:

You can use the intent flags like this.

Intent intent = new Intent(Class.class);    
intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
activity.startActivity(intent);

It will make only one activity be open at the top of the history stack.

回答4:

Since SO doesn't allow me to comment on other answers, I have to pollute this thread with a new answer.

Common answers for the "activity opens twice" problem and my experiences with these solutions (Android 7.1.1):

1. Disable button that starts the activity: Works but feels a little clumsy. If you have multiple ways to start the activity in your app (e.g. a button in the action bar AND by clicking on an item in a list view), you have to keep track of the enabled/disabled state of multiple GUI elements. Plus it's not very convenient to disable clicked items in a list view, for example. So, not a very universal approach.
2. launchMode="singleInstance": Not working with startActivityForResult(), breaks back navigation with startActivity(), not recommended for regular applications by Android manifest documentation.
3. launchMode="singleTask": Not working with startActivityForResult(), not recommended for regular applications by Android manifest documentation.
4. FLAG_ACTIVITY_REORDER_TO_FRONT: Breaks back button.
5. FLAG_ACTIVITY_SINGLE_TOP: Not working, activity is still opened twice.
6. FLAG_ACTIVITY_CLEAR_TOP: This is the only one working for me.

EDIT: This was for starting activities with startActivity(). When using startActivityForResult() I need to set both FLAG_ACTIVITY_SINGLE_TOP and FLAG_ACTIVITY_CLEAR_TOP.

回答5:

Let's say @wannik is right but if we have more than 1 button calling same action listener and i click two buttons once almost same time before starting next activity...

So it is good if you have field private boolean mIsClicked = false; and in the listener:

if(!mIsClicked)
{
    mIsClicked = true;
    Intent i = new Intent(this, AnotherActitivty.class);
    startActivity(i);
}

And onResume() we need to return the state:

@Override
protected void onResume() {
    super.onResume();

    mIsClicked = false;
}

What's the deifference between my and @wannik's answer?

If you set enabled to false in the listener of it's calling view other button using same listener will still be enabled. So to be sure that listener's action is not called twice you need to have something global that disables all callings of the listener(nevermind if it's new instance or no)

What is the difference between my answer and others?

They are thinking in right way but they are not thinking for future return to the same instance of the calling activity :)

回答6:

Use singleInstance to avoid activity to invoke twice.

<activity
            android:name=".MainActivity"
            android:label="@string/activity"
            android:launchMode = "singleInstance" />

回答7:

I think you're going about solving the problem the wrong way. Generally it is a bad idea for an activity to be making long-running web requests in any of its startup lifecycle methods (onCreate(), onResume(), etc). Really these methods should simply be used to instantiate and initialise objects your activity will use and should therefore be relatively quick.

If you need to be performing a web request then do this in a background thread from your newly launched activity (and show the loading dialog in the new activity). Once the background request thread completes it can update the activity and hide the dialog.

This then means your new activity should get launched immediately and prevent the double click from being possible.

回答8:

Hope this helps:

 protected static final int DELAY_TIME = 100;

// to prevent double click issue, disable button after click and enable it after 100ms
protected Handler mClickHandler = new Handler() {

    public void handleMessage(Message msg) {

        findViewById(msg.what).setClickable(true);
        super.handleMessage(msg);
    }
};

@Override
public void onClick(View v) {
    int id = v.getId();
    v.setClickable(false);
    mClickHandler.sendEmptyMessageDelayed(id, DELAY_TIME);
    // startActivity()
}`

回答9:

It was only working for me when startActivity(intent)

intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP);

回答10:

For this situation, I'll go for one of two approached, singleTask in manifest.xml OR a flag in the Activity's onResume() & onDestroy() methods respectively.

For the first solution: I prefer to use singleTask for the activity in the manifest rather than singleInstance, as per using singleInstance I figured out that in some occasions the activity creating a new separate instance for itself which result to have a two separate applications window in the running apps in bcakground and besides extra memory allocations that would result a very bad User Experience when the user opens the apps view to choose some app to resume. So, the better way is to have the activity defined at the manifest.xml like the following:

<activity
    android:name=".MainActivity"
    android:launchMode="singleTask"</activity>

you can check activity launch modes here.

---

For the second solution, you have to just define a static variable or a preference variable, for example:

public class MainActivity extends Activity{
    public static boolean isRunning = false;

    @Override
    public void onResume() {
        super.onResume();
        // now the activity is running
        isRunning = true;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // now the activity will be available again
        isRunning = false;
    }

}

and from the other side when you want to launch this activity, just check:

private void launchMainActivity(){
    if(MainActivity.isRunning)
        return;
    Intent intent = new Intent(ThisActivity.this, MainActivity.class);
    startActivity(intent);
}

回答11:

Other very very simple solution if you no want use onActivityResult() is disable the button for 2 seconds (or time you want), is not ideal, but can solve partly the problem is some cases and the code is simple:

   final Button btn = ...
   btn.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            //start activity here...
            btn.setEnabled(false);   //disable button

            //post a message to run in UI Thread after a delay in milliseconds
            btn.postDelayed(new Runnable() {
                public void run() {
                    btn.setEnabled(true);    //enable button again
                }
            },1000);    //1 second in this case...
        }
    });

回答12:

Just maintain one flag in button onClick method as:

public boolean oneTimeLoadActivity = false;

    myButton.setOnClickListener(new View.OnClickListener() {
          public void onClick(View view) {
               if(!oneTimeLoadActivity){
                    //start your new activity.
                   oneTimeLoadActivity = true;
                    }
        }
    });

回答13:

If you're using onActivityResult, you could use a variable to save state.

private Boolean activityOpenInProgress = false;

myButton.setOnClickListener(new View.OnClickListener() {
  public void onClick(View view) {
    if( activityOpenInProgress )
      return;

    activityOpenInProgress = true;
   //Load another activity with startActivityForResult with required request code
  }
});

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  if( requestCode == thatYouSentToOpenActivity ){
    activityOpenInProgress = false;
  }
}

Works on back button pressed too because request code is returned on event.

回答14:

Adding:

android:launchMode="singleTop"

Inside the activity tag in AndroidManifest.xml solved the issue.

回答15:

myButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View view) {
      myButton.setOnClickListener(null);
    }
});

回答16:

Use a flag variable set it to true, Check if its true just return else perform Activity Call.

You can also use setClickable(false) one executing the Activity Call

flg=false
 public void onClick(View view) { 
       if(flg==true)
         return;
       else
       { flg=true;
        // perform click}
    } 

回答17:

You can try this also

Button game = (Button) findViewById(R.id.games);
        game.setOnClickListener(new View.OnClickListener() 
        {
            public void onClick(View view) 
            {
                Intent myIntent = new Intent(view.getContext(), Games.class);
                startActivityForResult(myIntent, 0);
            }

        });

回答18:

You could just override startActivityForResult and use instance variable:

boolean couldStartActivity = false;

@Override
protected void onResume() {
    super.onResume();

    couldStartActivity = true;
}

@Override
public void startActivityForResult(Intent intent, int requestCode, Bundle options) {
    if (couldStartActivity) {
        couldStartActivity = false;
        intent.putExtra(RequestCodeKey, requestCode);
        super.startActivityForResult(intent, requestCode, options);
    }
}