在A片段点击碎片B按钮时更新的TextView [英] update TextView in fragment A when clicking button in fragment B

问题描述

我有两个片段在同一个活动坐在并排。当我在正确的片段（片段B）轻触一个按钮，我需要一个TextView左片段更新（片段A）。我已经到处寻找做到这一点的最好办法，但似乎没有任何工作，我的需要。可能有人可能给我的我会怎样code这样的例子？片段A是通过XML布局设置，并且B片段被载入编程到容器中。我曾尝试实现这一点通过使用碎片中的一个方法来更新文本，并呼吁从父活动的方法，该方法。然后，我呼吁从B片段父活动的方法。

I have two fragments sitting side by side in the same activity. When I touch a button in the right fragment (fragment B), I need a TextView in the left fragment to update (fragment A). I have looked all over for the best way to do this, but nothing seems to work for my needs. Could someone possibly give me an example of how I would code this? Fragment A is set through the XML layout, and fragment B gets loaded programmatically into a container. I have tried accomplishing this by using a method in fragment A to update the text, and calling on that method from a method in the parent activity. I then call on the method in the parent activity from fragment B.

这是在code在B片段声明的接口和调用方法在界面

This is the code in fragment B that declares the interface and calls a method in the interface

AttackCards attackCards; 

public interface AttackCards {
    public void deckSize();
}

public void onAttach(DeckBuilder deckBuilder) {
    super.onAttach(deckBuilder);

        attackCards = (AttackCards) deckBuilder;
        }

attackCards.deckSize(); //this is in my onclick methods

这是在code中实现接口，并呼吁在A片段的方法，活性

This is the code in the activity that implements the interface and calls the method in fragment A

public class DeckBuilder extends Activity implements AttackCards{

public void deckSize() {
    DeckBuilderFragment deckBuilderFragment = (DeckBuilderFragment)getFragmentManager().
            findFragmentById(R.id.deckbuilder_fragment);
    deckBuilderFragment.deckSize();
}

这是具有附加的共享preferences价值的内容

This is the method in fragment A that appends the textview with the contents of a shared preferences value

public void deckSize() {
deckSize = (TextView) getView().findViewById(R.id.decksize);  
final SharedPreferences defaultDeck = getActivity()
        .getSharedPreferences("defaultDeck", Context.MODE_PRIVATE);
deckSize.setText(String.valueOf(defaultDeck.getInt("decksize", 0)));
}

可悲的是这种尝试触摸按钮时，只需给我带来一个空指针。我得到一个空指针在

Sadly this attempt simply brings me a nullpointer when touching a button. I am getting a null pointer at

attackCards.deckSize(); //this is in my onclick methods

可能有人请帮助我如何做到这一点的例子是否正确？

Could someone please help me out with an example of how to do this correctly?

推荐答案

您可以定义在接口片段 B，并实现它的MainActivity。然后在回调方法（onClickOnB在这种情况下）设置在的TextView 的文本。你应该获得的TextView 在活动的参考的的onCreate（）在的setContentView（）。这样做是因为片段 A是静态的。否则，您可以创建在片段的公共方法 A这样你就可以得到片段的引用设置为从回调中的文本 A和调用这样的方法。

You can define an interface in Fragment B and implement it on the MainActivity. Then on the callback method (onClickOnB in this case) set the text on the TextView. You should obtain a reference of the TextView in the Activity's onCreate() after setContentView(). This works because Fragment A is static. Otherwise, you can create a public method inside Fragment A so you can set the text from inside the callback by getting a reference of Fragment A and calling such method.

片段 B

public class FragmentB extends Fragment implements onClickListener{
ClickOnB listener;
public void setOnFragmentBClickListener(ClickOnB listener){
this.listener = listener;

}

@Override

public void onClick(View v){
//stringMessage is a `String` you will pass to `Fragment` A to update its `TextView`
listener.onClickOnB(stringMessage);
}

interface ClickOnB{
public void onClickOnB(String message);
}

}

MainActivity

public class MainActivity extends Activity implements ClickOnB{
@Override   
protected onCreate(Bundle savedInstanceState){

//Get a reference of `Fragment` B somewhere in your code after you added it dynamically and set the listener.
((FragmentB)getFragmentManager().findFragmentByTag("FragmentB")).setOnFragmentBClickListener(this);

}

@Override
public void onClickOnB(String message){

//Set the text to the `TextView` here (I am assuming you get a reference of the `TextView` in onCreate() after inflating your layout.

mTextView.setText(message);

}
}

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