How to update fragment/update fragment ui from activity?

Question

Pageviewer.java code:

    //hide status bar/action bar on single tap
    package com.app.imageswiper;

    import android.app.ActionBar;
    import android.app.Dialog;
    import android.app.Fragment;
    import android.app.FragmentManager;
    import android.app.FragmentTransaction;
    import android.content.Context;
    import android.content.Intent;
    import android.content.SharedPreferences;
    import android.net.Uri;
    import android.os.Handler;
    import android.preference.PreferenceManager;
    import android.support.design.widget.TabLayout;
    import android.support.v4.view.GestureDetectorCompat;
    import android.support.v4.view.MotionEventCompat;
    import android.support.v4.view.ViewPager;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.GestureDetector;
    import android.view.Gravity;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.MotionEvent;
    import android.view.View;
    import android.view.Window;
    import android.view.WindowManager;
    import android.widget.Button;
    import android.widget.ImageView;
    import android.widget.LinearLayout;
    import android.widget.RelativeLayout;
    import android.widget.TextView;
    import android.widget.Toast;

    public class Pageviwer extends AppCompatActivity {

        private Integer[] mImageIds = {R.drawable.page001, R.drawable.page002,
                R.drawable.page003};
        private static final String DEBUG_TAG = "pageviwer ";
        ImageView imageView;
        float startXValue = 1;
        public int num;
        public int click;
        protected static final String TAG = "Pageviwer";
        private GestureDetector mGestureDetector;
        public SharedPreferences prefs;
        public static int Bookmark = 0;
        public static int Pageno = 0;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            prefs = PreferenceManager.getDefaultSharedPreferences(this);
            int Bookmark1 = prefs.getInt("Bookmark", 0);
            Bookmark = Bookmark1;

            prefs = PreferenceManager.getDefaultSharedPreferences(this);
            int Pageno1 = prefs.getInt("Pageno", 0);
            Pageno = Pageno1;


            setContentView(R.layout.pageviwer);
            imageView = (ImageView) findViewById(R.id.image_place_holder);
            imageView.setImageResource(mImageIds[0]);
            TextView tv1 = (TextView) findViewById(R.id.pageno);
            tv1.setText("" + (num + 1));
            Toast.makeText(getApplicationContext(), "value is " + num, Toast.LENGTH_LONG).show();
            setupGestureDetector();
            hideActionBar(); // hide action bar after 1 second
        }


        private void setupGestureDetector() {


            mGestureDetector = new GestureDetector(this,

                    new GestureDetector.SimpleOnGestureListener() {

                        //Detecting Swipe/Fling Direction
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2,
                                               float velocityX, float velocityY) {
                            Log.i(TAG, "onFling");
                            if (e1.getX() < e2.getX()) {
                                Log.d(TAG, "Left to Right swipe performed");
                                if (num == 2) {
                                    num = num;
                                } else {
                                    imageView.setImageResource(mImageIds[num + 1]);
                                    num = num + 1;
                                }
                                TextView tv1 = (TextView) findViewById(R.id.pageno);
                                tv1.setText("" + (num + 1));
                                Toast.makeText(getApplicationContext(), "value is " + num, Toast.LENGTH_LONG).show();
                            }

                            if (e1.getX() > e2.getX()) {
                                Log.d(TAG, "Right to Left swipe performed");
                                if (num == 0) {
                                    num = num;
                                } else {
                                    imageView.setImageResource(mImageIds[num - 1]);
                                    num = num - 1;
                                }
                                TextView tv1 = (TextView) findViewById(R.id.pageno);
                                tv1.setText("" + (num + 1));

                                Toast.makeText(getApplicationContext(), "value is " + num, Toast.LENGTH_LONG).show();
                            }
                            return true;
                        }

                        //detecting single tap
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            Log.i(TAG, "onSingleTapUp");
                            Toast.makeText(getApplicationContext(), "Single Tap ", Toast.LENGTH_LONG).show();
                            //Remove notification bar and action bar
                            if (click == 0) {
                                getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
                                getWindow().addFlags(WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN);
                                if (getSupportActionBar() != null) getSupportActionBar().hide();
                                click = 1;
                            }
                            //Return notification bar and action bar
                            else {
                                getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
                                getWindow().getDecorView().setSystemUiVisibility(
                                        View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                                                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
                                if (getSupportActionBar() != null) getSupportActionBar().show();
                                click = 0;
                            }
                            return true;
                        }
                    });
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {

            if (mGestureDetector != null) {
                return mGestureDetector.onTouchEvent(event);
            } else {
                return super.onTouchEvent(event);
            }

        }

        public void hideActionBar() {
            Handler h = new Handler();
            h.postDelayed(new Runnable() {
                @Override
                public void run() {
                    // DO DELAYED STUFF
                    getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
                    getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN);
                    if (getSupportActionBar() != null) getSupportActionBar().hide();
                    click = 1;
                }
            }, 1000); //  1000 milliseconds (1 second)
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {

            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();


            if (id == com.app.imageswiper.R.id.action_settings) {
                Bookmark=1;
                prefs.edit().putInt("Bookmark", Bookmark).commit();
                prefs.edit().putInt("Pageno", num).commit();
                Toast.makeText(getApplicationContext(), "Bookmark value is "+Bookmark, Toast.LENGTH_LONG).show();



            }


            return super.onOptionsItemSelected(item);


        }
    }

ViewPagerAdapter code:

package com.app.imageswiper;

/**
 * Created by Jaffer on 14-Apr-16.
 */
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.Toast;

public class Bookmarks extends Fragment {
    public SharedPreferences prefs;
    public static int Bookmark = 0;
    public static int Pageno = 0;
    Button sendButton = null;
    View inflatedView = null;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
        int Bookmark1 = prefs.getInt("Bookmark", 0);
        Bookmark = Bookmark1;

        prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
        int Pageno1 = prefs.getInt("Pageno", 0);
        Pageno = Pageno1;

        this.inflatedView = inflater.inflate(R.layout.bookmarks, container, false);

        sendButton = (Button) inflatedView.findViewById(R.id.bookmark);
        if(Bookmark==1){sendButton.setText("Page "+Pageno);}
        else {sendButton.setText("No Bookmark ");}

        if(sendButton == null)
        {
            Log.d("debugCheck", "HeadFrag: sendButton is null");
            return inflatedView;
        }
        sendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getActivity(), Pageviwer.class);
                startActivity(intent);
            }
        });
        return inflatedView;
    }
}

bookmarks.xml code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:id="@+id/bookmarks">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAllCaps="false"
        style="@style/Widget.AppCompat.Button.Borderless"
        android:id="@+id/bookmark"
        android:layout_alignParentBottom="true" />
    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@android:color/darker_gray"/>

</LinearLayout>

I don't know how to update the button text from Pageviewer.java for the button with R.id.bookmark that shows up on the Bookmarks fragment on the click of menu item R.id.action_settings. I want to do this so that the button text corresponds to the page that is being bookmarked. I tried alot of things but to no avail. Can someone please help me with anything?

Thanks in advance

Answer 1

Create a method in your fragment to update the text of your button.

public void updateText(String newText){
  //assuming button is globally declared in your fragment.
  button.setText(newText);
}

Instead of Gesture Detector you could use a ViewPager which supports swiping to the left and right.You can find a sample implementation here .

Then in your Activty,implement PageChanegListener on ViewPager .

viewPager.addOnPageChangeListener(new OnPageChangeListener() {
    public void onPageScrollStateChanged(int state) {}
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}

    public void onPageSelected(int position) {
        // Check if this is the page you want.You have to implement viewpager's adapter with getItem(index) which returns a fragment at that index.
        BookMarkFragment fragment  (BookMarkFragment)mAdapter.getItem(position);
        fragment.updateText(newText);
    };
});

Answer 2

You should save the state of a button somewhere. Your field int Bookmark == 0 , so expression sendButton.setText("Page "+Pageno); never execute. Save the state in SharedPreferences and get this state. Like this:

prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
int isBookmark = prefs.getInt("Bookmark", 0);
int mPageno = prefs.getInt("Pageno", 0);
...
if(isBookmark == 1){
    sendButton.setText("Page " + mPageno);
} else {
    sendButton.setText("No Bookmark");
}