Question

MainActivity

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, ViewGroup container, Bundle savedInsanceState) {
        return inflater.inflate(R.layout.second_fragment, container, false);
    }
}

他们的XML文件：

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 就像上一篇文章一样，只有android:text="Second!"

这是奇怪的事情，当我点击Start1按钮4次然后我得到First!这个词的4倍，直到这里一切正常。如果我单击Start2按钮，我会期望删除前面的4个片段并添加一个新片段，其外观为Second!。这是我从文档中理解的：

替换添加到容器的现有片段。这与使用相同的containerViewId添加的所有当前添加的片段调用remove（Fragment），然后使用此处给出的相同参数添加（int，Fragment，String）基本相同。

但这是我得到的：

我试着阅读源代码，也许我发现了“问题”在哪里，我想知道你的想法，如果是我，我在某个地方犯了错误。

以下是来自 BackStackRecord.java ，run()方法的代码段：

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);
                                }
                            }
                        }
                    }

以下是 FragmentManager.java ：

的摘录

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);
        }
    }

正如您所看到的，removeFragment方法从mAdded中删除了一个框架，但在run()方法之后，i索引未被修改，它从在它离开的地方，它会失去一些元素......

Answer 1

使用linearlayout作为容器无法实现此方案。

如果您尝试将此片段用作linearlayout中的容器，则可以实现此目的。请参阅此链接以获得进一步说明

Android - fragment .replace() doesn't replace content - puts it on top

否则，请使用以下代码进行按钮点击操作

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();
        }
    });

希望这会对你有所帮助..谢谢

replace（）与多片段无法正常工作

1 个答案: