Android ViewPager中片段之间的通信
我正在尝试这样做: 除了我用的是一个残缺的StatePageRadapter 我有一个活动,有两个片段(片段A和片段B) FragmentA有一个edittext和一个按钮,FragmentB有一个textview 现在我想要的是,每当我在编辑文本中输入一些内容并单击按钮时,我的文本视图中就会出现一些内容 main活动:Android ViewPager中片段之间的通信,android,android-fragments,fragmentstatepageradapter,Android,Android Fragments,Fragmentstatepageradapter,我正在尝试这样做: 除了我用的是一个残缺的StatePageRadapter 我有一个活动,有两个片段(片段A和片段B) FragmentA有一个edittext和一个按钮,FragmentB有一个textview 现在我想要的是,每当我在编辑文本中输入一些内容并单击按钮时,我的文本视图中就会出现一些内容 main活动: public class MainActivity extends FragmentActivity { ViewPager viewPager = null;
public class MainActivity extends FragmentActivity {
ViewPager viewPager = null;
String TabFragmentB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new FragmentA();
}
if (i == 1)
{
fragment = new FragmentB();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
}
public void setTabFragmentB(String t) {
TabFragmentB = t;
}
public String getTabFragmentB() {
return TabFragmentB;
}
}
public class FragmentA extends Fragment {
EditText et;
Button bt;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fraga, container, false);
et = (EditText)v.findViewById(R.id.edit1);
bt = (Button)v.findViewById(R.id.button1);
bt.setOnClickListener(Click);
return v;
}
OnClickListener Click = new OnClickListener(){
@Override
public void onClick(View v) {
String textPassToB = et.getText().toString();
String TabOfFragmentB = ((MainActivity)getActivity()).getTabFragmentB();
FragmentB fragmentB = (FragmentB)getActivity()
.getSupportFragmentManager()
.findFragmentByTag(TabOfFragmentB);
fragmentB.updateText(textPassToB);
}
};
}
public class FragmentB extends Fragment {
TextView tv;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragb, container, false);
tv = (TextView)v.findViewById(R.id.text1);
String myTag = getTag();
((MainActivity)getActivity()).setTabFragmentB(myTag);
return v;
}
public void updateText(String t){
tv.setText(t);
}
}
FATAL EXCEPTION: main
java.lang.NullPointerException
at lmf.sample1.FragmentA$1.onClick(FragmentA.java:43)
at android.view.View.performClick(View.java:4212)
at android.view.View$PerformClick.run(View.java:17476)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
片段a:
public class MainActivity extends FragmentActivity {
ViewPager viewPager = null;
String TabFragmentB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new FragmentA();
}
if (i == 1)
{
fragment = new FragmentB();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
}
public void setTabFragmentB(String t) {
TabFragmentB = t;
}
public String getTabFragmentB() {
return TabFragmentB;
}
}
public class FragmentA extends Fragment {
EditText et;
Button bt;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fraga, container, false);
et = (EditText)v.findViewById(R.id.edit1);
bt = (Button)v.findViewById(R.id.button1);
bt.setOnClickListener(Click);
return v;
}
OnClickListener Click = new OnClickListener(){
@Override
public void onClick(View v) {
String textPassToB = et.getText().toString();
String TabOfFragmentB = ((MainActivity)getActivity()).getTabFragmentB();
FragmentB fragmentB = (FragmentB)getActivity()
.getSupportFragmentManager()
.findFragmentByTag(TabOfFragmentB);
fragmentB.updateText(textPassToB);
}
};
}
public class FragmentB extends Fragment {
TextView tv;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragb, container, false);
tv = (TextView)v.findViewById(R.id.text1);
String myTag = getTag();
((MainActivity)getActivity()).setTabFragmentB(myTag);
return v;
}
public void updateText(String t){
tv.setText(t);
}
}
FATAL EXCEPTION: main
java.lang.NullPointerException
at lmf.sample1.FragmentA$1.onClick(FragmentA.java:43)
at android.view.View.performClick(View.java:4212)
at android.view.View$PerformClick.run(View.java:17476)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
片段b:
public class MainActivity extends FragmentActivity {
ViewPager viewPager = null;
String TabFragmentB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new FragmentA();
}
if (i == 1)
{
fragment = new FragmentB();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
}
public void setTabFragmentB(String t) {
TabFragmentB = t;
}
public String getTabFragmentB() {
return TabFragmentB;
}
}
public class FragmentA extends Fragment {
EditText et;
Button bt;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fraga, container, false);
et = (EditText)v.findViewById(R.id.edit1);
bt = (Button)v.findViewById(R.id.button1);
bt.setOnClickListener(Click);
return v;
}
OnClickListener Click = new OnClickListener(){
@Override
public void onClick(View v) {
String textPassToB = et.getText().toString();
String TabOfFragmentB = ((MainActivity)getActivity()).getTabFragmentB();
FragmentB fragmentB = (FragmentB)getActivity()
.getSupportFragmentManager()
.findFragmentByTag(TabOfFragmentB);
fragmentB.updateText(textPassToB);
}
};
}
public class FragmentB extends Fragment {
TextView tv;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragb, container, false);
tv = (TextView)v.findViewById(R.id.text1);
String myTag = getTag();
((MainActivity)getActivity()).setTabFragmentB(myTag);
return v;
}
public void updateText(String t){
tv.setText(t);
}
}
FATAL EXCEPTION: main
java.lang.NullPointerException
at lmf.sample1.FragmentA$1.onClick(FragmentA.java:43)
at android.view.View.performClick(View.java:4212)
at android.view.View$PerformClick.run(View.java:17476)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
LogCat:
public class MainActivity extends FragmentActivity {
ViewPager viewPager = null;
String TabFragmentB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new FragmentA();
}
if (i == 1)
{
fragment = new FragmentB();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
}
public void setTabFragmentB(String t) {
TabFragmentB = t;
}
public String getTabFragmentB() {
return TabFragmentB;
}
}
public class FragmentA extends Fragment {
EditText et;
Button bt;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fraga, container, false);
et = (EditText)v.findViewById(R.id.edit1);
bt = (Button)v.findViewById(R.id.button1);
bt.setOnClickListener(Click);
return v;
}
OnClickListener Click = new OnClickListener(){
@Override
public void onClick(View v) {
String textPassToB = et.getText().toString();
String TabOfFragmentB = ((MainActivity)getActivity()).getTabFragmentB();
FragmentB fragmentB = (FragmentB)getActivity()
.getSupportFragmentManager()
.findFragmentByTag(TabOfFragmentB);
fragmentB.updateText(textPassToB);
}
};
}
public class FragmentB extends Fragment {
TextView tv;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragb, container, false);
tv = (TextView)v.findViewById(R.id.text1);
String myTag = getTag();
((MainActivity)getActivity()).setTabFragmentB(myTag);
return v;
}
public void updateText(String t){
tv.setText(t);
}
}
FATAL EXCEPTION: main
java.lang.NullPointerException
at lmf.sample1.FragmentA$1.onClick(FragmentA.java:43)
at android.view.View.performClick(View.java:4212)
at android.view.View$PerformClick.run(View.java:17476)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
每当我单击第一个片段上的按钮时,我的应用程序就会崩溃。到底是什么问题?在您切换到FragmentB.updateText(textPassToB)之前,FragmentB甚至不会被创建代码>为您提供NullPointerException 您需要将编辑文本中的文本存储在活动中,稍后(如果)创建碎片B时,您需要从中读取值
public class TextChangedEvent {
public String newText;
public TextChangedEvent(String newText) {
this.newText = newText;
}
}
然后,在片段A中:
//when text changes
EventBus bus = EventBus.getDefault();
bus.post(new TextChangedEvent(newText));
在片段B中:
EventBus bus = EventBus.getDefault();
//Register to EventBus
@Override
public void onCreate(SavedInstanceState savedState) {
bus.register(this);
}
//catch Event from fragment A
public void onEvent(TextChangedEvent event) {
yourTextView.setText(event.newText);
}
片段可以访问这些父活动。
因此,最简单的方法是在父活动中注册回调 更新:提交缓存已添加到MainActivity
public class MainActivity extends FragmentActivity {
private OnButtonClicked mOnButtonClicked;
private String mSubmitCache;
public interface OnButtonClicked {
void submit(final String s);
}
public void setOnButtonClicked(final OnButtonClicked c) {
mOnButtonClicked = c;
// deliver cached string, if any
if (TextUtils.isEmpty(mSubmitCache) == false) {
c.submit(mSubmitCache);
}
}
public void buttonClicked(final String s) {
if (mOnButtonClicked == null) {
// if FragmentB doesn't exist jet, cache value
mSubmitCache = s;
return;
}
mOnButtonClicked.submit(s);
}
}
public class FragmentA extends Fragment implements OnClickListener {
private MainActivity mMain;
private Button mButton;
@Override public onAttach(Activity a) {
mMain = (MainActivity) a;
}
@Override public void onClick(View v) {
mMain.buttonClicked("send this to FragmentB.");
}
}
public class FragmentB extends Fragment implements MainActivity.OnButtonClicked {
private MainActivity mMain;
private TextView mTextView;
// Called when the fragment's activity has been created
// and this fragment's view hierarchy instantiated
@Override public void onActivityCreated(Bundle savedState) {
mMain = (MainActivity) getActivity();
mMain.setOnButtonClicked(this);
}
@Override void submit(final String s) {
mTextView.setText(s);
}
}
我使用了上面Mr.的解决方案。但除此之外,Android Studio要求我在OneEvent
方法之前添加@Subscribe
注释
像这样:
@Subscribe
public void onEvent(TextChangedEvent event) {
textView.setText(event.newText);
}
根据:
订阅者实现事件处理方法(也称为“订阅者方法”),在发布事件时将调用这些方法。这些方法是用@Subscribe注释定义的。请注意,使用EventBus 3可以自由选择方法名称(没有像EventBus 2中那样的命名约定)
我已经编辑了答案,并建议如何解决。你的意思是我将把文本从FragmentA传递到Activity。然后当我在FragmentB中时,我将从Activity中获取它?没错。只需在Activity中为实例变量提供getter和setter,然后在fragmets中使用
MyActivity act=(MyActivity)getActivity();act.getMyVariable()
。这不是最干净的方法,但对于像您这样的简单情况,它是可以接受的。只需单击答案左侧的复选标记。它将变为绿色。公共类TextChangedEvent是否在MainActivity中?不,它是一个独立类(当然,如果需要,您可以将其声明为activity的内部类)(使用公共静态修饰符),并将其称为MainActivity.TextChangedEvent)。当然,片段B只有在[fragment B]已创建的情况下才会接收事件。因此,您需要在fragmennt的onCreate()中设置初始文本。最好的方法是确保添加“@Subscribe”以上是您想要从中获取信息的方法。否则它将崩溃。我认为这是一种比使用广播或任何第三方库更好的方法!