Java – replace() does not work with multiple fragments

Main activities

package example.antonio.activitydemo;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.support.v4.app.*;

public class MainActivity extends FragmentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final FragmentManager fragmentManager = getSupportFragmentManager();

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FirstFragment fragment = new FirstFragment();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

                fragmentTransaction.add(R.id.container,fragment);
                fragmentTransaction.commit();
            }
        });

        Button button2 = (Button) findViewById(R.id.button2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SecondFragment fragment = new SecondFragment();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

                fragmentTransaction.replace(R.id.container,fragment);
                fragmentTransaction.commit();
            }
        });
    }
}

FirstFragment

package example.antonio.activitydemo;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.view.View;

public class FirstFragment extends Fragment {

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

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInsanceState) {
        return inflater.inflate(R.layout.first_fragment,container,false);
    }
}

SecondFragment

package example.antonio.activitydemo;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.view.View;

public class SecondFragment extends Fragment {

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

    @Override
    public View onCreateView(LayoutInflater inflater,Bundle savedInsanceState) {
        return inflater.inflate(R.layout.second_fragment,false);
    }
}

Their XML file:

main_ activity. xml

<?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:id="@+id/container"
    android:orientation="vertical">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start1"
        android:id="@+id/button"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start2"
        android:id="@+id/button2"/>

</LinearLayout>

first_ fragment. xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#000000">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="First!"
        android:textColor="#ffffff"/>


</FrameLayout>

second_ fragment. XML is just like the previous one, only Android: text = "second!"

This is a strange thing. When I click the start 1 button four times, and then I get four times the word first!, Until everything is normal here If I click the start 2 button, I will expect to delete the previous four clips and add a new one, which looks like second This is what I understand from the document:

But this is what I get:

I try to read the source code. Maybe I find out what a "problem" is. I want to know what you think. If it was me, I made a mistake somewhere

Here is the backstackrecord Java fragment, run () method:

case OP_REPLACE: {
                    Fragment f = op.fragment;
                    int containerId = f.mContainerId;
                    if (mManager.mAdded != null) {
                        for (int i = 0; i < mManager.mAdded.size(); i++) {
                            Fragment old = mManager.mAdded.get(i);
                            if (FragmentManagerImpl.DEBUG) {
                                Log.v(TAG,"OP_REPLACE: adding=" + f + " old=" + old);
                            }
                            if (old.mContainerId == containerId) {
                                if (old == f) {
                                    op.fragment = f = null;
                                } else {
                                    if (op.removed == null) {
                                        op.removed = new ArrayList<Fragment>();
                                    }
                                    op.removed.add(old);
                                    old.mNextAnim = op.exitAnim;
                                    if (mAddToBackStack) {
                                        old.mBackStackNesting += 1;
                                        if (FragmentManagerImpl.DEBUG) {
                                            Log.v(TAG,"Bump nesting of "
                                                    + old + " to " + old.mBackStackNesting);
                                        }
                                    }
                                    mManager.removeFragment(old,mTransition,mTransitionStyle);
                                }
                            }
                        }
                    }

This is fragmentmanager Java fragment:

public void removeFragment(Fragment fragment,int transition,int transitionStyle) {
        if (DEBUG) Log.v(TAG,"remove: " + fragment + " nesting=" + fragment.mBackStackNesting);
        final boolean inactive = !fragment.isInBackStack();
        if (!fragment.mDetached || inactive) {
            if (false) {
                // Would be nice to catch a bad remove here,but we need
                // time to test this to make sure we aren't crashes cases
                // where it is not a problem.
                if (!mAdded.contains(fragment)) {
                    throw new IllegalStateException("Fragment not added: " + fragment);
                }
            }
            **if (mAdded != null) {
                mAdded.remove(fragment);
            }**
            if (fragment.mHasMenu && fragment.mMenuVisible) {
                mNeedMenuInvalidate = true;
            }
            fragment.mAdded = false;
            fragment.mRemoving = true;
            moveToState(fragment,inactive ? Fragment.INITIALIZING : Fragment.CREATED,transition,transitionStyle,false);
        }
    }

As you can see, the removefragment method deletes a frame from madded, but after the run () method, the I index is not modified. It restarts from where it left, and some elements will be lost

Solution

This scheme cannot be implemented using LinearLayout as a container

You can do this if you try to use this clip as a container in the linear layout See this link for further instructions

Android – fragment . replace() doesn’t replace content – puts it on top

Otherwise, click the button with the following code,

Button button = (Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            FirstFragment fragment = new FirstFragment();
            FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();

            fragmentTransaction.add(R.id.container,fragment).addToBackStack(null);
            fragmentTransaction.commit();
        }
    });

    Button button2 = (Button) findViewById(R.id.button2);
    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            SecondFragment fragment = new SecondFragment();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            for(int i=0; i < getSupportFragmentManager().getBackStackEntryCount(); i++)
                getSupportFragmentManager().popBackStack();
            fragmentTransaction.replace(R.id.container,fragment);
            fragmentTransaction.commit();
        }
    });

I hope this will help you thank you