Java 按钮onclick无法使用我的第二个片段android

我正在为一个计算器编写代码，分别有两个片段fragmenOne和fragmentTwo。FragmentOne是我的默认片段，包含加法、减法和数字等基本功能。第二个片段FragmentII包含sin tan cos等高级功能。我的第二个片段中的按钮不起作用，也不附加编辑框。但是我的fragmentOne中的按钮工作正常。如果我先进入fragmentTwo，然后进入fragmentOne，按钮在fragmentOne中也不起作用。请用英文说明这个问题。下面提供了代码和图片

MainActivity.java

package com.example.fragmentstest;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.ExpressionBuilder;
import de.congrace.exp4j.UnknownFunctionException;
import de.congrace.exp4j.UnparsableExpressionException;

public class MainActivity extends Activity implements View.OnClickListener {
Button one, two, three, four, five, six, seven, eight, nine, zero, add,
sub, mul, div, equal, decimal, cancel, sin, cos, tan, open_bracket, close_bracket;
EditText disp;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);
    one = (Button) findViewById(R.id.one);
    two = (Button) findViewById(R.id.two);
    three = (Button) findViewById(R.id.three);
    four = (Button) findViewById(R.id.four);
    five = (Button) findViewById(R.id.five);
    six = (Button) findViewById(R.id.six);
    seven = (Button) findViewById(R.id.seven);
    eight = (Button) findViewById(R.id.eight);
    nine = (Button) findViewById(R.id.nine);
    zero = (Button) findViewById(R.id.zero);

    add = (Button) findViewById(R.id.add);
    sub = (Button) findViewById(R.id.sub);
    mul = (Button) findViewById(R.id.mul);
    div = (Button) findViewById(R.id.div);
    equal = (Button) findViewById(R.id.equal);
    decimal = (Button) findViewById(R.id.decimal);

    sin = (Button) findViewById(R.id.sin);
    cos = (Button) findViewById(R.id.cos);
    tan = (Button) findViewById(R.id.tan);
    open_bracket = (Button) findViewById(R.id.open_bracket);
    close_bracket = (Button)findViewById(R.id.close_bracket);

    disp = (EditText) findViewById(R.id.display_panel);
    cancel = (Button) findViewById(R.id.cancel); 
    try {
        one.setOnClickListener(this);
        two.setOnClickListener(this);
        three.setOnClickListener(this);
        four.setOnClickListener(this);
        five.setOnClickListener(this);
        six.setOnClickListener(this);
        seven.setOnClickListener(this);
        eight.setOnClickListener(this);
        nine.setOnClickListener(this);
        zero.setOnClickListener(this);

        add.setOnClickListener(this);
        sub.setOnClickListener(this);
        mul.setOnClickListener(this);
        div.setOnClickListener(this);
        equal.setOnClickListener(this);
        decimal.setOnClickListener(this);
        cancel.setOnClickListener(this);
        sin.setOnClickListener(this);
        cos.setOnClickListener(this);
        tan.setOnClickListener(this);
        open_bracket.setOnClickListener(this);
        close_bracket.setOnClickListener(this);
    } catch (Exception e) {
    }
}

public void selectFrag(View view) {
    Fragment fr;

    if (view == findViewById(R.id.button2)) {
        fr = new FragmentTwo();

    } else {
        fr = new FragmentOne();

    }

    FragmentManager fm = getFragmentManager();
    FragmentTransaction fragmentTransaction = fm.beginTransaction();
    fragmentTransaction.replace(R.id.fragment_place, fr);
    fragmentTransaction.commit();

}

@Override
public void onClick(View v) {
    Editable str = disp.getText();
    switch (v.getId()) {
    case R.id.zero:
        str = str.append(zero.getText());
        disp.setText(str);
        break;
    case R.id.one:
        str = str.append(one.getText());
        disp.setText(str);
        break;
    case R.id.two:
        str = str.append(two.getText());
        disp.setText(str);
        break;
    case R.id.three:
        str = str.append(three.getText());
        disp.setText(str);
        break;
    case R.id.four:
        str = str.append(four.getText());
        disp.setText(str);
        break;
    case R.id.five:
        str = str.append(five.getText());
        disp.setText(str);
        break;
    case R.id.six:
        str = str.append(six.getText());
        disp.setText(str);
        break;
    case R.id.seven:
        str = str.append(seven.getText());
        disp.setText(str);
        break;
    case R.id.eight:
        str = str.append(eight.getText());
        disp.setText(str);
        break;
    case R.id.nine:
        str = str.append(nine.getText());
        disp.setText(str);
        break;
    case R.id.add:
        str = str.append(add.getText());
        disp.setText(str);
        break;
    case R.id.sub:
        str = str.append(sub.getText());
        disp.setText(str);
        break;
    case R.id.mul:
        str = str.append(mul.getText());
        disp.setText(str);
        break;
    case R.id.div:
        str = str.append(div.getText());
        disp.setText(str);
        break;
    case R.id.decimal:
        str = str.append(decimal.getText());
        disp.setText(str);
        break;
    case R.id.sin:
        str = str.append(sin.getText());
        disp.setText(str);
        break;
    case R.id.cos:
        str = str.append(cos.getText());
        disp.setText(str);
        break;
    case R.id.tan:
        str = str.append(tan.getText());
        disp.setText(str);
        break;  
    case R.id.open_bracket:
        str = str.append(open_bracket.getText());
        disp.setText(str);
        break;
    case R.id.close_bracket:
        str = str.append(close_bracket.getText());
        disp.setText(str);
        break;  
    case R.id.cancel:
        disp.setText("");
        disp.setHint("Perform Operation");
        break;  
    case R.id.equal:
        String val;
        val = disp.getText().toString();
        Calculable calc = null;
        try {
            Calculable result = new ExpressionBuilder(val).build();
            disp.setText(Double.toString(result.calculate()));
            /* size_num = result.calculate(); */
        } catch (UnknownFunctionException e) {
            disp.setText("ERROR");
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnparsableExpressionException e) {
            disp.setText("ERROR");
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        break;

}

}
}

activity_main.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:orientation="vertical" >

<EditText 
   android:id="@+id/display_panel"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:hint="@string/dispHint"/> 
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >

<Button
    android:id="@+id/button1"
    style="?android:attr/buttonBarButtonStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="selectFrag"
    android:paddingRight="45dp"
    android:text="@string/basic" />

<Button
    android:id="@+id/button2"
    style="?android:attr/buttonBarButtonStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="selectFrag"
    android:paddingLeft="25dp"
    android:paddingRight="25dp"
    android:text="@string/adv" />

</LinearLayout>
<fragment
    android:id="@+id/fragment_place"
    android:name="com.example.fragmentstest.FragmentOne"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

</LinearLayout>

---

FragmentOne.java代码与FragmentTwo.java相同，只是类名为FragmentOne且位于“R.layout.fragment\u one”中。

创建活动时，活动\u main.xml膨胀后，它将只包含fragment\u one.xml中的视图。此时将不存在fragment_two.xml的视图（因为该片段将在运行时动态添加）。这意味着findViewById（R.id.sin）将在onCreate函数中返回null，现在有了注册onClickListener的视图。这就是为什么在注册ClickListeners时需要try-catch块（以避免NullPointerException）的原因

您应该在Fragments类中注册onClickListeners，而不是在活动中注册。尝试从Activity类中删除setOnClickListener调用，并在activities中执行此操作

public class FragmentTwo extends Fragment{
@Override
   public View onCreateView(LayoutInflater inflater,
  ViewGroup container, Bundle savedInstanceState) {    
  // Inflate the layout for this fragment    
  View view = inflater.inflate(
          R.layout.fragment_two, container, false);
  Button sin =  (Button) view.findViewById(R.id.sin);
  sin.setOnClickListener(...);
  //other onItemListeners go here
  return view;
 }
}

您可以通过调用getActivity从片段类访问MainActivity，并将其强制转换为MainActivity

((MainActivity)getActivity())

---

Ashoka试试这段代码这会对你有所帮助。这里我分享主要活动，片段一，片段二类代码，基本上我们在片段中使用按钮，所以最好在片段中处理事件，并且在你的主要活动中像这样使用处理程序更新edittext

主要活动课

public class MainActivity extends Activity  {
EditText disp;
static Handler mHandler;
String str ;

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

    setContentView(R.layout.activity_main);

    disp = (EditText) findViewById(R.id.display_panel);
    str = disp.getText().toString();


    mHandler = new Handler()
    {
        public void handleMessage(android.os.Message msg) 
        {

            super.handleMessage(msg);
            if (msg.what == 1)
            {
                str = str + "seven";
            }
            else 
            {
                str = str + "sin";
            }
            disp.setText(str);

        }
    };
}

public void selectFrag(View view) {
    Fragment fr = null;

        if (view == findViewById(R.id.button2))
        {
            fr = new FragmentTwo();
            FragmentManager fm = getFragmentManager();
            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fragment_place, fr);
            fragmentTransaction.addToBackStack(null);

            fragmentTransaction.commit();
        } 
        else
        {
            fr = new FragmentOne();
            FragmentManager fm = getFragmentManager();
            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fragment_place, fr);
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
        }



}

}

片段一类

  // Inflate the layout for this fragment

    View v = inflater.inflate(R.layout.fragment_one, container, false);

    Button seven = (Button)v.findViewById(R.id.seven);
    seven.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Message msgtab=MainActivity.mHandler.obtainMessage();
            msgtab.what= 1;
            MainActivity.mHandler.sendMessage(msgtab);

        }
    });


  return v;

和片段二类

View v = inflater.inflate(R.layout.fragment_two, container, false);
    Button sin = (Button)v.findViewById(R.id.sin);
    sin.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Message msgtab=MainActivity.mHandler.obtainMessage();
            msgtab.what=2;
            MainActivity.mHandler.sendMessage(msgtab);

        }
    });
    return v;

---

你能扩展一下什么是。。。在setOnclickListenser中，包含以及如何通过调用getActivity从片段类访问MainActivity。我的意思是应该在主活动上写些什么。@balazs您应该在那里设置View.OnClickListener实现。目前这是你的主要活动。因此sin.setOnClickListener（（（MainActivity）getActivity（））应该可以工作。这意味着您在片段类中注册一个OnClickListener，该类将由MainActivity处理。另一种解决方案是在片段类中实现OnClickListener：公共类FragmentTwo扩展了Fragment implements View.OnClickListener，然后使用sin.setOnClickListener设置clickListener（此选项）；在片段类中。在这种情况下，Fragment类将处理click事件。

public class MainActivity extends Activity  {
EditText disp;
static Handler mHandler;
String str ;

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

    setContentView(R.layout.activity_main);

    disp = (EditText) findViewById(R.id.display_panel);
    str = disp.getText().toString();


    mHandler = new Handler()
    {
        public void handleMessage(android.os.Message msg) 
        {

            super.handleMessage(msg);
            if (msg.what == 1)
            {
                str = str + "seven";
            }
            else 
            {
                str = str + "sin";
            }
            disp.setText(str);

        }
    };
}

public void selectFrag(View view) {
    Fragment fr = null;

        if (view == findViewById(R.id.button2))
        {
            fr = new FragmentTwo();
            FragmentManager fm = getFragmentManager();
            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fragment_place, fr);
            fragmentTransaction.addToBackStack(null);

            fragmentTransaction.commit();
        } 
        else
        {
            fr = new FragmentOne();
            FragmentManager fm = getFragmentManager();
            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fragment_place, fr);
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
        }



}

  // Inflate the layout for this fragment

    View v = inflater.inflate(R.layout.fragment_one, container, false);

    Button seven = (Button)v.findViewById(R.id.seven);
    seven.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Message msgtab=MainActivity.mHandler.obtainMessage();
            msgtab.what= 1;
            MainActivity.mHandler.sendMessage(msgtab);

        }
    });


  return v;

View v = inflater.inflate(R.layout.fragment_two, container, false);
    Button sin = (Button)v.findViewById(R.id.sin);
    sin.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Message msgtab=MainActivity.mHandler.obtainMessage();
            msgtab.what=2;
            MainActivity.mHandler.sendMessage(msgtab);

        }
    });
    return v;