使用 FragmentPagerAdapter 从父片段正确调用片段选项卡中的函数

Question

我使用 FragmentPagerAdapter:

创建了标签页

public class SectionsPagerAdapter extends FragmentPagerAdapter {
static final int PAGE_COUNT = 2;

public SectionsPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int index) {
    switch (index) {
    case 0:
        return new SessionDetails();
    case 1:
        return new SessionScoreTable();
    }
    return null;
}

@Override
public int getCount() {
    return PAGE_COUNT;
}}

我需要通过单击另一个选项卡上的按钮来更新一个选项卡。

父 FragmentActivity 有：

fragSessionDetails = (SessionDetails) mSectionsPagerAdapter.getItem(0);

并且有 function:

public void setSessionCompleted(){
    fragSessionDetails.processSessionCompleted();
}

这是从另一个选项卡 (SessionScoreTable) 调用的。

SessionDetails 选项卡具有功能：

    public void processSessionCompleted(){
    Log.d(TAG,"processSessionCompleted" );
        bSave.setEnabled(false);
        }

b保存按钮。

在日志中我有 NullPointerException 行 - bSave.setEnabled(false):

06-30 16:20:45.414: D/STS_SessionDetails(15876): processSessionCompleted 06-30 16:20:45.414: D/AndroidRuntime(15876): Shutting down VM 06-30 16:20:45.414: W/dalvikvm(15876): threadid=1: thread exiting with uncaught exception (group=0x41b62d88) 06-30 16:20:45.414: E/AndroidRuntime(15876): Exception 06-30 16:20:45.414: E/AndroidRuntime(15876): FATAL EXCEPTION: main 06-30 16:20:45.414: E/AndroidRuntime(15876): Process: com.vvv.vvvvvvvvvvvvv, PID: 15876 06-30 16:20:45.414: E/AndroidRuntime(15876): java.lang.NullPointerException 06-30 16:20:45.414: E/AndroidRuntime(15876): at com.vvv.vvvvvvvvvvvvv.SessionDetails.processSessionCompleted(SessionDetails.java:237) 06-30 16:20:45.414: E/AndroidRuntime(15876): at com.vvv.vvvvvvvvvvvvv.Session.setSessionCompleted(Session.java:151)

我好像丢了什么东西，但不知道是什么东西。请帮忙。

Answer 1

行

fragSessionDetails = (SessionDetails) mSectionsPagerAdapter.getItem(0);

是非常糟糕的做法。更好的方法是通过更改方法在运行时访问片段：

public void setSessionCompleted(){
    ((SessionDetails) mSectionsPagerAdapter.getItem(0)).processSessionCompleted();
}

Answer 2

终于，我找到了解决方案。

public class SectionsPagerAdapter extends FragmentPagerAdapter {
static final int PAGE_COUNT = 2;
private SessionDetails fragSessionDetails;
private SessionScoreTable fragSessionScoreTable;

public SectionsPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int index) {
    switch (index) {
    case 0:
        return new SessionDetails();
    case 1:
        return new SessionScoreTable();
    return null;
}

@Override
public int getCount() {
    return PAGE_COUNT;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    Fragment createdFragment = (Fragment) super.instantiateItem(container, position);
    // save the appropriate reference depending on position
    switch (position) {
        case 0:
            fragSessionDetails = (SessionDetails) createdFragment;
            break;
        case 1:
            fragSessionScoreTable = (SessionScoreTable) createdFragment;
            break;
    }
    return createdFragment;
}

public SessionDetails getFragSessionDetails(){
    return fragSessionDetails;
}

public SessionScoreTable getFragSessionScoreTable(){
    return fragSessionScoreTable;
}}

和

    public void setSessionCompleted(){
    SessionDetails fragSessionDetails = mSectionsPagerAdapter.getFragSessionDetails();
    if (fragSessionDetails != null) {
        Log.d(TAG, "fragSessionDetails");
        fragSessionDetails.processSessionCompleted();
    }
}

想法来自

使用 FragmentPagerAdapter 从父片段正确调用片段选项卡中的函数

Correctly to call function in fragment tab from parent fragment with FragmentPagerAdapter

android

android-fragments

fragmentpageradapter